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-
-<title> Advanced Linux Sound Architecture - Library API</title>
-
-<H1 align=center>Advanced Linux Sound Architecture - Library API </H1>
-
-<p>
-
-<H3 align=center><b>Jaroslav Kysela <perex@suse.cz></b> with assistance from Alan Robinson and Fred Floberg</H3>
-
-<p>
-
-<H3 align=center>1998-11-11 </H3>
-
-<p>
-<center> <i>This document describes, in full detail, the Advanced Linux
-Sound Architecture library API. </i>
-<p>
-</center>
-<H1>Contents </H1><A href="#tth_sEc1"
->1 Introduction</A><br>
-<A href="#tth_sEc2"
->2 Error Codes</A><br>
- <A href="#tth_sEc2.1"
->2.1 Error Codes in Detail</A><br>
- <A href="#tth_sEc2.2"
->2.2 Functions</A><br>
-<A href="#tth_sEc3"
->3 Control Interface</A><br>
- <A href="#tth_sEc3.1"
->3.1 Low-Level Layer</A><br>
- <A href="#tth_sEc3.1.1"
->3.1.1 Examples</A><br>
-<A href="#tth_sEc4"
->4 Mixer Interface</A><br>
- <A href="#tth_sEc4.1"
->4.1 Low-Level Layer</A><br>
- <A href="#tth_sEc4.1.1"
->4.1.1 Examples</A><br>
-<A href="#tth_sEc5"
->5 Digital Audio (PCM) Interface</A><br>
- <A href="#tth_sEc5.1"
->5.1 Low-Level Layer</A><br>
- <A href="#tth_sEc5.1.1"
->5.1.1 Example</A><br>
- <A href="#tth_sEc5.2"
->5.2 PCM Loopback Interface</A><br>
-<A href="#tth_sEc6"
->6 RawMidi Interface</A><br>
- <A href="#tth_sEc6.1"
->6.1 Low Level Layer</A><br>
- <A href="#tth_sEc6.1.1"
->6.1.1 Example</A><br>
-
-<p>
- <H2><A NAME="tth_sEc1">
-1</A> Introduction</H2>
-
-<p>
-The Advanced Linux Sound Architecture comes with a kernel API & library API.
-This document describes the library API and how it interfaces with the kernel
-API. The kernal API will probably never be documented in standalone form.
-
-<p>
-Application programmers should use the library API rather than kernel API. The
-Library offers 100% of the functionally of the kernel API, but add major improvements
-in usability, making the application code simpler and better looking. In addition,
-some of the some fixes/compatibility code may be placed in the library code
-instead of the kernel driver.
-
-<p>
-For a complete list of all variables and functions in the API you should look
-at the following header files:
-
-<p>
-
-<UL>
-<li> /usr/include/sys/asoundlib.h
-
-<li> /usr/include/linux/asound.h
-
-<li> /usr/include/linux/asoundid.h
-</UL>
-<p>
- <H2><A NAME="tth_sEc2">
-2</A> Error Codes</H2>
-
-<p>
-All functions return int (or some sort of signed value). If this value is negative
-it represents an error code. Codes up to <i>SND_ERROR_BEGIN (500000)</i>
-represent standard system errors. Codes equal to or greather than this value
-represent sound library API errors. All error codes begin with the prefix <i>SND_ERROR_</i>.
-
-<p>
- <H3><A NAME="tth_sEc2.1">
-2.1</A> Error Codes in Detail</H3>
-
-<p>
-
-<table border>
-<tr><td align="center">SND_ERROR_UNCOMPATIBLE_VERSION</td><td align="center">500000</td></td></table>
-
-
-<p>
-This error is caused if the driver uses an incompatible kernel API for this
-interface and hence the library doesn't know how this API can be used.
-
-<p>
- <H3><A NAME="tth_sEc2.2">
-2.2</A> Functions</H3>
-
-<p>
-
-<H4>const char *snd_strerror(int errnum) </H4>
-
-<p>
-This function converts an error code to a string. Its functionality is the same
-as the <i>strerror</i> function from the standard C library, but this function
-returns error message strings for sound error codes, as well.
-
-<p>
- <H2><A NAME="tth_sEc3">
-3</A> Control Interface</H2>
-
-<p>
-The control interface gives applications various information about the currently
-installed sound driver in the system. The interface should be used to detect
-if another sound interface is present for a selected soundcard or, for example,
-to create a list of devices (MIXER, PCM etc) from which the user can select.
-
-<p>
- <H3><A NAME="tth_sEc3.1">
-3.1</A> Low-Level Layer</H3>
-
-<p>
-
-<H4>int snd_cards(void)</H4>
-
-<p>
-Returns the number of soundcards present in the system, if any. Otherwise it
-returns a negative value, which maps to an error code. This function will return
-0 if no soundcards are detected.
-
-<p>
-
-<H4>unsigned int snd_cards_mask(void)</H4>
-
-<p>
-Returns the bitmap of soundcards present in the system, if any. This function
-will return 0 if no soundcards are detected. The first soundcard is represented
-with bit 0 (0x00000001). See the documentation on installing ALSA and /etc/conf.modules
-configuration for information on assigning numbers to soundcards.
-
-<p>
-
-<H4>int snd_card_name(const char *name)</H4>
-
-<p>
-Returns soundcard number for appropriate soundcard name. String <i>name</i>
-can contain word identification for card (ALSA driver allows the user choose
-card identification using snd_id module parameter) or soundcard index (1-N)
-encoded into ASCII.
-
-<p>
-
-<H4>int snd_ctl_open(void **handle, int card)</H4>
-
-<p>
-Creates a new handle and opens communication with the kernel sound control interface
-for soundcard number <i>card</i> (0-N). The function also checks if the protocol
-is compatible, so as to prevent the use of old programs with a new kernel API.
-Function returns zero if successful, otherwise an error code is returned.
-
-<p>
-
-<H4>int snd_ctl_close(void *handle)</H4>
-
-<p>
-Frees all resources allocated with control handle and closes the kernel sound
-control interface. This function returns zero if successful, otherwise it returns
-an error code.
-
-<p>
-
-<H4>int snd_ctl_file_descriptor(void *handle)</H4>
-
-<p>
-Returns a file descriptor for the kernel sound control interface. This function
-is normally only used in very special cases. This function returns a negative
-error code if an error was encountered.
-
-<p>
-
-<H4>int snd_ctl_hw_info(void *handle, snd_ctl_hw_info_t *info)</H4>
-
-<p>
-Fills the info structure with data about the sound hardware referenced by handle.
-This function returns zero if successful, otherwise it returns an error code.
-
-<p>
-
-<DL compact> <dt><b></b></dt>
- <dd>
-<i>/* driver has MIDI interface */ </i>
-
-<p>
-#define SND_CTL_GCAPS_MIDI 0x0000001
-
-<p>
-<i>/* soundcard has synthesizer */</i>
-
-<p>
-#define SND_CTL_LCAPS_SYNTH 0x0000001
-
-<p>
-<i>/* soundcard has RAW FM/OPL3 */</i>
-
-<p>
-#define SND_CTL_LCAPS_RAWFM 0x0000002
-</DL>
-<p>
-
-
-<p>
-
-<DL compact> <dt><b></b></dt>
- <dd>
-struct snd_ctl_hw_info {
-
-<p>
- <i>/* type of card - see SND_CARD_TYPE_XXXX */</i>
-
-<p>
- unsigned int type;
-
-<p>
- <i>/* global capabilities - see SND_CTL_GCAPS_XXXX*/</i>
-
-<p>
- unsigned int gcaps;
-
-<p>
- <i>/* local capabilities ¯ see SND_CTL_LCAPS_XXXX */</i>
-
-<p>
- unsigned int lcaps;
-
-<p>
- <i>/* count of PCM devices (0 to N) */</i>
-
-<p>
- unsigned int pcmdevs;
-
-<p>
- <i>/* count of MIXER devices (0 to N)*/</i>
-
-<p>
- unsigned int mixerdevs;
-
-<p>
- <i>/* count of raw MIDI devices (0 to N) */</i>
-
-<p>
- unsigned int mididevs;
-
-<p>
- <i>/* ID of card (user selectable) */</i>
-
-<p>
- char id[80];
-
-<p>
- <i>/* name/info text about soundcard */</i>
-
-<p>
- char name[80];
-
-<p>
- <i>/* count of control switches */</i>
-
-<p>
- unsigned int switches;
-
-<p>
- <i>/* reserved for future use */</i>
-
-<p>
- unsigned char reserved[124];
-
-<p>
-};
-</DL>
-<p>
-
-<H4>int snd_ctl_switches(void *handle)</H4>
-
-<p>
-Returns the number of control switches. In this context 'switch' means universal
-control interface between kernel and application which allows various types
-of control. Function returns count if successful, otherwise it returns an error
-code. Return value should be zero if the soundcard doesn't have any control
-switches.
-
-<p>
-
-<H4>int snd_ctl_switch(void *handle, const char *switch_id)</H4>
-
-<p>
-Returns the index for the switch with the name <i>switch_id</i>. This function
-returns switch index if successful, otherwise it returns an error code.
-
-<p>
-
-<H4>int snd_ctl_switch_read(void *handle int switchn snd_ctl_switch_t
-*data)</H4>
-
-<p>
-Fills the <i>*data</i> structure with data about the switch with index <i>switchn</i>.
-This function returns zero if successful, otherwise it returns an error code.
-
-<p>
-
-<DL compact> <dt><b></b></dt>
- <dd>
-<i>/* 0 or 1 (enable member of union) */</i>
-
-<p>
-#define SND_CTL_SW_TYPE_BOOLEAN 0
-
-<p>
-<i>/* 0 to 255 - from low to high (data8[0] member of union) */</i>
-
-<p>
-#define SND_CTL_SW_TYPE_BYTE 1
-
-<p>
-<i>/* 0 to 65535 - from low to high (data16[0] member of union) */</i>
-
-<p>
-#define SND_CTL_SW_TYPE_WORD 2
-
-<p>
-<i>/* 0 to 4294967296 ¯ from low to high (data32[0] member of union) */</i>
-
-<p>
-#define SND_CTL_SW_TYPE_DWORD 3
-
-<p>
-<i>/* user type - no type control */</i>
-
-<p>
-#define SND_CTL_SW_TYPE_USER (~0)
-</DL>
-<p>
-
-
-<p>
-
-<DL compact> <dt><b></b></dt>
- <dd>
-<i>/* well known (named) switches */</i>
-
-<p>
-#define SND_CTL_SW_JOYSTICK "Joystick"
-
-<p>
-#define SND_CTL_SW_JOYSTICK_ADDRESS "Joystick Address"
-
-<p>
-#define SND_CTL_SW_JOYSTICK_SPEED "Joystick Speed"
-</DL>
-<p>
-
-
-<p>
-
-<DL compact> <dt><b></b></dt>
- <dd>
-struct snd_ctl_switch {
-
-<p>
- <i>/* switch index (filled by application) */</i>
-
-<p>
- unsigned int switchn;
-
-<p>
- <i>/* indentification of switch (for driver) */</i>
-
-<p>
- unsigned char name[32];
-
-<p>
- <i>/* type of switch value - See SND_CTL_SW_TYPE_XXXX */</i>
-
-<p>
- unsigned int type;
-
-<p>
- <i>/* low range value */</i>
-
-<p>
- unsigned int low;
-
-<p>
- <i>/* high range value */</i>
-
-<p>
- unsigned int high;
-
-<p>
- union {
-
-<p>
- unsigned int enable; <i>/* 0 = off 1 = on */</i>
-
-<p>
- unsigned char data8[32]; <i>/* 8-bit data */</i>
-
-<p>
- unsigned short data16[16]; <i>/* 16-bit data */</i>
-
-<p>
- unsigned int data32[8]; <i>/* 32-bit data */</i>
-
-<p>
- } value;
-
-<p>
- <i>/* reserved for future use ¯ must be zero !!! */</i>
-
-<p>
- unsigned char reserved[32];
-
-<p>
-}
-</DL>
-<p>
-
-<H4>int snd_ctl_switch_write(void *handle int switchn snd_ctl_switch_t
-*data)</H4>
-
-<p>
-Writes the <i>*data</i> structure with data about the switch with index
-<i>switchn</i> to kernel. This function returns zero if successful, otherwise
-it returns an error code.
-
-<p>
-
-<H4>int snd_ctl_mixer_info(void *handle, int dev, snd_mixer_info_t *info)</H4>
-
-<p>
-Fills the *info structure with data about the mixer device. Returns zero if
-successful, otherwise it returns an error code. Details about the <i>snd_mixer_info_t</i>
-structure are in the <b>Mixer Interface</b> section. The argument <i>dev</i>
-specifies the device number for the appropriate soundcard. Its range is 0 to
-N where N is determined by <i>struct snd_ctl_hw_info->mixerdevs - 1</i>.
-It should be used to collect information about mixer devices.
-
-<p>
-
-<H4>int snd_ctl_mixer_switches(void *handle)</H4>
-
-<p>
-Returns count of mixer switches. In this context 'switch' means universal control
-interface between kernel and application which allows various types control.
-This function returns count if successful, otherwise it returns an error code.
-Return value should be zero if soundcard doesn't have any mixer switches.
-
-<p>
-
-<H4>int snd_ctl_mixer_switch(void *handle, const char *switch_id)</H4>
-
-<p>
-Returns the index for the switch with the name <i>switch_id</i>. This function
-returns switch index if successful, otherwise it returns an error code.
-
-<p>
-
-<H4>int snd_ctl_mixer_switch_read(void *handle int switchn snd_mixer_switch_t
-*data)</H4>
-
-<p>
-Fills the <i>*data</i> structure with data about the switch with index <i>switchn</i>.
-This function returns zero if successful, otherwise it returns an error code.
-Details about the <i>snd_mixer_switch_t</i> structure are in the <b>Mixer
-Interface</b> section.
-
-<p>
-
-<H4>int snd_ctl_mixer_switch_write(void *handle int switchn snd_mixer_switch_t
-*data)</H4>
-
-<p>
-Writes the <i>*data</i> structure with data about switch with index <i>switchn</i>
-to kernel. Function returns zero if successful, otherwise it returns an error
-code. Details about the <i>snd_mixer_switch_t</i> structure are in the
-<b>Mixer Interface</b> Interface section.
-
-<p>
-
-<H4>int snd_ctl_pcm_info(void *handle, int dev, snd_pcm_info_t *info)</H4>
-
-<p>
-Fills the <i>*info</i> structure with data about the PCM device. Function
-returns zero if successful, otherwise it returns an error code. Details about
-the <i>snd_pcm_info_t</i> structure are in the <b>Digital Audio (PCM)</b>
-Interface section. The argument <i>dev</i> selects the device number for the
-sound card referenced by <i>*handle</i>. Its range is 0 to N where N is
-<i>struct snd_ctl_hw_info->pcmdevs - 1</i>. This function will work if
-the selected PCM device is busy, too. It should be used to collect information
-about PCM devices without exclusive lock.
-
-<p>
-
-<H4>int snd_ctl_pcm_playback_info(void *handle, int dev, snd_pcm_playback_info_t
-*info) </H4>
-
-<p>
-Fills the <i>*info</i> structure with data about the PCM device and playback
-direction. Function returns zero if successful, otherwise it returns an error
-code. Details about the <i>snd_pcm_playback_info_t</i> structure are in
-the <b>Digital Audio (PCM) Interface</b> section. The argument <i>dev</i>
-selects the device number for the sound card referenced by <i>*handle</i>.
-Its range is 0 to N where N is <i>struct snd_ctl_hw_info->pcmdevs -
-1</i>. This function will work if the selected PCM device is busy, too. It should
-be used to collect information about PCM devices without exclusive lock.
-
-<p>
-
-<H4>int snd_ctl_pcm_playback_switches(void *handle)</H4>
-
-<p>
-Returns count of PCM playback switches. In this context 'switch' means universal
-control interface between kernel and application which allows various types
-of control. Function returns count if successful, otherwise it returns an error
-code. Return value should be zero if sound card doesn't have any PCM playback
-switch.
-
-<p>
-
-<H4>int snd_ctl_pcm_playback_switch(void *handle, const char *switch_id)</H4>
-
-<p>
-Returns index for switch with name <i>switch_id</i>. Function returns switch
-index if successful, otherwise it returns an error code.
-
-<p>
-
-<H4>int snd_ctl_pcm_playback_switch_read(void *handle int switchnsnd_pcm_switch_t *data)</H4>
-
-<p>
-Fills the <i>*data</i> structure with data about switch with index <i>switchn</i>.
-Function returns zero if successful, otherwise it returns an error code. Details
-about the <i>snd_pcm_switch_t</i> structure are in the <b>Digital
-Audio (PCM)</b> Interface section.
-
-<p>
-
-<H4>int snd_ctl_pcm_playback_switch_write(void *handle int switchnsnd_pcm_switch_t *data)</H4>
-
-<p>
-Writes the <i>*data</i> structure with data about switch with index <i>switchn</i>
-to kernel. Function returns zero if successful, otherwise it returns an error
-code. Details about the <i>snd_pcm_switch_t</i> structure are in the <b>Digital
-Audio (PCM)</b> Interface section.
-
-<p>
-
-<H4>int snd_ctl_pcm_record_info(void *handle, int dev, snd_pcm_record_info_t
-*info)</H4>
-
-<p>
-Fills the <i>*info</i> structure with data about the PCM device and record
-direction. Function returns zero if successful, otherwise it returns an error
-code. Details about the <i>snd_pcm_record_info_t</i> structure are in
-the <b>Digital Audio (PCM) Interface</b> section. The argument <i>dev</i>
-selects the device number for the sound card referenced by <i>*handle</i>.
-Its range is 0 to N where N is <i>struct snd_ctl_hw_info->pcmdevs -
-1</i>. This function will work if the selected PCM device is busy, too. It should
-be used to collect information about PCM devices without exclusive lock.
-
-<p>
-
-<H4>int snd_ctl_pcm_record_switches(void *handle)</H4>
-
-<p>
-Returns count of PCM record switches. In this context 'switch' means universal
-control interface between kernel and application which allows various types
-of control. Function returns count if successful, otherwise it returns an error
-code. Return value should be zero if sound card doesn't have any PCM record
-switch.
-
-<p>
-
-<H4>int snd_ctl_pcm_record_switch(void *handle, const char *switch_id)</H4>
-
-<p>
-Returns index for switch with name <i>switch_id</i>. Function returns switch
-index if successful, otherwise it returns an error code.
-
-<p>
-
-<H4>int snd_ctl_pcm_record_switch_read(void *handle int switchnsnd_pcm_switch_t *data)</H4>
-
-<p>
-Fills the <i>*data</i> structure with data about switch with index <i>switchn</i>.
-Function returns zero if successful, otherwise it returns an error code. Details
-about the <i>snd_pcm_switch_t</i> structure are in the <b>Digital
-Audio (PCM)</b> Interface section.
-
-<p>
-
-<H4>int snd_ctl_pcm_record_switch_write(void *handle int switchnsnd_pcm_switch_t *data)</H4>
-
-<p>
-Writes the <i>*data</i> structure with data about switch with index <i>switchn</i>
-to kernel. Function returns zero if successful, otherwise it returns an error
-code. Details about the <i>snd_pcm_switch_t</i> structure are in the <b>Digital
-Audio (PCM)</b> Interface section.
-
-<p>
-
-<H4>int snd_ctl_rawmidi_info(void *handle, int dev, snd_rawmidi_info_t
-*info)</H4>
-
-<p>
-Fills the <i>*info</i> structure with data about the rawmidi device. Function
-returns zero if successful, otherwise it returns an error code. Details about
-the <i>snd_rawmidi_info_t</i> structure are in the <b>RawMidi Interface</b>
-section. The argument <i>dev</i> selects the device number for the sound card
-referenced by <i>*handle</i>. Its range is 0 to N where N is <i>struct
-snd_ctl_hw_info->mididevs - 1</i>. This function will work if the selected rawmidi
-device is busy, too. It should be used to collect information about rawmidi
-devices without exclusive lock.
-
-<p>
-
-<H4>int snd_ctl_rawmidi_output_info(void *handle, int dev, snd_rawmidi_output_info_t
-*info) </H4>
-
-<p>
-Fills the <i>*info</i> structure with data about the rawmidi device and
-output direction. Function returns zero if successful, otherwise it returns
-an error code. Details about the <i>snd_pcm_playback_info_t</i> structure
-are in the <b>RawMidi Interface</b> section. The argument <i>dev</i> selects
-the device number for the sound card referenced by <i>*handle</i>. Its range
-is 0 to N where N is <i>struct snd_ctl_hw_info->mididevs - 1</i>. This
-function will work if the selected rawmidi device is busy, too. It should be
-used to collect information about rawmidi devices without exclusive lock.
-
-<p>
-
-<H4>int snd_ctl_rawmidi_output_switches(void *handle)</H4>
-
-<p>
-Returns count of rawmidi output switches. In this context 'switch' means universal
-control interface between kernel and application which allows various types
-of control. Function returns count if successful, otherwise it returns an error
-code. Return value should be zero if sound card doesn't have any control switch.
-
-<p>
-
-<H4>int snd_ctl_rawmidi_output_switch(void *handle, const char *switch_id)</H4>
-
-<p>
-Returns index for switch with name <i>switch_id</i>. Function returns switch
-index if successful, otherwise it returns an error code. Return value should
-be zero if sound card doesn't have any rawmidi output switch.
-
-<p>
-
-<H4>int snd_ctl_rawmidi_output_switch_read(void *handle int switchnsnd_rawmidi_switch_t *data)</H4>
-
-<p>
-Fills the <i>*data</i> structure with data about switch with index <i>switchn</i>.
-Function returns zero if successful, otherwise it returns an error code. Details
-about the <i>snd_rawmidi_switch_t</i> structure are in the <b>RawMidi
-Interface</b> section.
-
-<p>
-
-<H4>int snd_ctl_rawmidi_output_switch_write(void *handle int switchnsnd_rawmidi_switch_t *data)</H4>
-
-<p>
-Writes the <i>*data</i> structure with data about switch with index <i>switchn</i>
-to kernel. Function returns zero if successful, otherwise it returns an error
-code. Details about the <i>snd_rawmidi_switch_t</i> structure are in the
-<b>RawMidi Interface</b> section.
-
-<p>
-
-<H4>int snd_ctl_rawmidi_input_info(void *handle, int dev, snd_rawmidi_input_info_t
-*info)</H4>
-
-<p>
-Fills the <i>*info</i> structure with data about the rawmidi device and
-input direction. Function returns zero if successful, otherwise it returns an
-error code. Details about the <i>snd_rawmidi_record_info_t</i> structure
-are in the <b>RawMidi Interface</b> section. The argument <i>dev</i> selects
-the device number for the sound card referenced by <i>*handle</i>. Its range
-is 0 to N where N is <i>struct snd_ctl_hw_info->pcmdevs - 1</i>. This function
-will work if the selected rawmidi device is busy, too. It should be used to
-collect information about rawmidi devices without exclusive lock.
-
-<p>
-
-<H4>int snd_ctl_rawmidi_input_switches(void *handle)</H4>
-
-<p>
-Returns count of rawmidi input switches. In this context 'switch' means universal
-control interface between kernel and application which allows various types
-of control. Function returns count if successful, otherwise it returns an error
-code. Return value should be zero if sound card doesn't have any rawmidi input
-switch.
-
-<p>
-
-<H4>int snd_ctl_rawmidi_input_switch(void *handle, const char *switch_id)</H4>
-
-<p>
-Returns index for switch with name <i>switch_id</i>. Function returns switch
-index if successful, otherwise it returns an error code.
-
-<p>
-
-<H4>int snd_ctl_rawmidi_input_switch_read(void *handle int switchnsnd_pcm_switch_t *data)</H4>
-
-<p>
-Fills the <i>*data</i> structure with data about switch with index <i>switchn</i>.
-Function returns zero if successful, otherwise it returns an error code. Details
-about the <i>snd_rawmidi_switch_t</i> structure are in the <b>RawMidi
-Interface</b> Interface section.
-
-<p>
-
-<H4>int snd_ctl_rawmidi_input_switch_write(void *handle int switchnsnd_pcm_switch_t *data)</H4>
-
-<p>
-Writes the <i>*data</i> structure with data about switch with index <i>switchn</i>
-to kernel. Function returns zero if successful, otherwise it returns an error
-code. Details about the <i>snd_rawmidi_switch_t</i> structure are in the
-<b>RawMidi Interface</b> section.
-
-<p>
- <H4><A NAME="tth_sEc3.1.1">
-3.1.1</A> Examples</H4>
-
-<p>
-The following example shows how all PCM devices can be detected for the first
-sound card (#0) in the system.
-
-<p>
-
-<DL compact> <dt><b></b></dt>
- <dd>
-int card = 0, err;
-
-<p>
-void *handle;
-
-<p>
-snd_ctl_hw_info_t info;<br>
-
-<p>
-if ((err = snd_ctl_open(&handle, card)) < 0) {
-
-<p>
- fprintf(stderr, "open failed: %s\n", snd_strerror(err));
-
-<p>
- return;
-
-<p>
-}
-
-<p>
-if ((err = snd_ctl_hw_info(handle, &info)) < 0) {
-
-<p>
- fprintf(stderr, "hw info failed: %s\n",
-
-<p>
- snd_strerror(err));
-
-<p>
- snd_ctl_close(handle);
-
-<p>
- return;
-
-<p>
-}
-
-<p>
-printf("Installed PCM devices for card #i: %i\n",
-
-<p>
- card + 1, info.pcmdevs);
-
-<p>
-snd_ctl_close(handle);
-</DL>
-<p>
- <H2><A NAME="tth_sEc4">
-4</A> Mixer Interface</H2>
-
-<p>
-The Mixer Interface allows applications to change the volume level of a sound
-card's input/output channels in both the linear range percentage range
-(0-100) and in decibels. It also supports features like hardware mute, input
-sound source, stereo signal routing etc.
-
-<p>
- <H3><A NAME="tth_sEc4.1">
-4.1</A> Low-Level Layer</H3>
-
-<p>
-Mixer devices aren't opened exclusively. This allows applications to open a
-device multiple times with one or more processes.
-
-<p>
-
-<H4>int snd_mixer_open(void **handle, int card, int device) </H4>
-
-<p>
-Creates new handle and opens a connection to the kernel sound mixer interface
-for sound card number <i>card</i> (0-N) and mixer device number <i>device</i>.
-Also checks if protocol is compatible to prevent use of old programs with new
-kernel API. Function returns zero if successful, otherwise it returns an error
-code.
-
-<p>
-
-<H4>int snd_mixer_close(void *handle)</H4>
-
-<p>
-Frees all resources allocated to the mixer handle and closes its connection
-to the kernel sound mixer interface. Function returns zero if successful, otherwise
-it returns an error code.
-
-<p>
-
-<H4>int snd_mixer_file_descriptor(void *handle)</H4>
-
-<p>
-Returns the file descriptor for the connection to the kernel sound mixer interface.
-This function should be used only in very special cases. Function returns a
-negative error code if an error was encountered.
-
-<p>
-The file descriptor should be used for the <i>select(2)</i> synchronous multiplexer
-function for determining read direction. Applications should call <i>snd_mixer_read()</i>
-function if some data is waiting to be read. It is recommended that you do this,
-since it leaves place for this function to handle some new kernel API specifications.
-
-<p>
-
-<H4>int snd_mixer_channels(void *handle) </H4>
-
-<p>
-Returns the count of mixer channels for appropriate mixer device, otherwise
-the return value is negative, and signifies an error code. Never returns zero.
-
-<p>
-
-<H4>int snd_mixer_info(void *handle, snd_mixer_info_t *info) </H4>
-
-<p>
-Fills the <i>*info</i> structure with information about the mixer associated
-with <i>*handle</i>. Returns zero if successful, otherwise it returns an
-error code.
-
-<p>
-
-<DL compact> <dt><b></b></dt>
- <dd>
-<i>/* mixer can do only exclusive record */</i>
-
-<p>
-#define SND_MIXER_INFO_CAP_EXCL_RECORD 0x00000001
-</DL>
-<p>
-
-
-<p>
-
-<DL compact> <dt><b></b></dt>
- <dd>
-struct snd_mixer_info {
-
-<p>
- <i>/* type of sound card - SND_CARD_TYPE_XXXX */</i>
-
-<p>
- unsigned int type;
-
-<p>
- <i>/* count of mixer devices */</i>
-
-<p>
- unsigned int channels;
-
-<p>
- <i>/* some flags about this device (SND_MIXER_INFO_CAP_XXXX) */</i>
-
-<p>
- unsigned int caps;
-
-<p>
- <i>/* ID of this mixer */</i>
-
-<p>
- unsigned char id[32];
-
-<p>
- <i>/* name of this device */</i>
-
-<p>
- unsigned char name[80];
-
-<p>
- <i>/* reserved for future use */</i>
-
-<p>
- char reserved[ 32 ];
-
-<p>
-};
-</DL>
-<p>
-
-<H4>int snd_mixer_switches(void *handle)</H4>
-
-<p>
-Returns count of mixer switches. In this context 'switch' means universal control
-interface between kernel and application which allows various types of control.
-Function returns count if successful, otherwise it returns an error code. Return
-value will be zero if sound card doesn't have any mixer switch.
-
-<p>
-
-<H4>int snd_mixer_switch(void *handle, const char *switch_id)</H4>
-
-<p>
-Returns index for switch with name <i>switch_id</i>. Function returns switch
-index if successful, otherwise it returns an error code.
-
-<p>
-
-<H4>int snd_mixer_switch_read(void *handle int switchn snd_mixer_switch_t
-*data)</H4>
-
-<p>
-Fills the <i>*data</i> structure with data about switch with index <i>switchn</i>.
-Function returns zero if successful, otherwise it returns an error code.
-
-<p>
-
-<DL compact> <dt><b></b></dt>
- <dd>
-<i>/* 0 or 1 (enable member of union) */</i>
-
-<p>
-#define SND_MIXER_SW_TYPE_BOOLEAN 0
-
-<p>
-<i>/* 0 to 255 - from low to high (data8[0] member of union) */</i>
-
-<p>
-#define SND_MIXER_SW_TYPE_BYTE 1
-
-<p>
-<i>/* 0 to 65535 - from low to high (data16[0] member of union) */</i>
-
-<p>
-#define SND_MIXER_SW_TYPE_WORD 2
-
-<p>
-<i>/* 0 to 4294967296 ¯ from low to high (data32[0] member of union) */</i>
-
-<p>
-#define SND_MIXER_SW_TYPE_DWORD 3
-
-<p>
-<i>/* user type - no type control */</i>
-
-<p>
-#define SND_MIXER_SW_TYPE_USER (~0)
-</DL>
-<p>
-
-
-<p>
-
-<DL compact> <dt><b></b></dt>
- <dd>
-<i>/* well known (named) switches */</i>
-
-<p>
-#define SND_MIXER_SW_LOUDNESS "Loudness" <i>/* bass boost */</i>
-
-<p>
-#define SND_MIXER_SW_SIM_STEREO "Simulated Stereo Enhancement"
-
-<p>
-#define SND_MIXER_SW_3D "3D Stereo Enhancement"
-
-<p>
-<i>/* microphone gain */</i>
-
-<p>
-#define SND_MIXER_SW_MIC_GAIN "MIC Gain"
-
-<p>
-<i>/* microphone auto gain control */</i>
-
-<p>
-#define SND_MIXER_SW_MIC_GAIN "MIC Auto-Gain-Control"
-
-<p>
-<i>/* change microphone impedance */</i>
-
-<p>
-#define SND_MIXER_SW_MIC_GAIN "Change MIC Impedance"
-
-<p>
-<i>/* change line-in to output */</i>
-
-<p>
-#define SND_MIXER_SW_MIC_GAIN "Line In to Output"
-
-<p>
-#define SND_MIXER_SW_IEC958OUT "IEC-958 (S/PDIF) Output"
-
-<p>
-#define SND_MIXER_SW_IEC958IN "IEC-958 (S/PDIF) Input"
-</DL>
-<p>
-
-
-<p>
-
-<DL compact> <dt><b></b></dt>
- <dd>
-struct snd_mixer_switch {
-
-<p>
- <i>/* switch index (filled by application) */</i>
-
-<p>
- unsigned int switchn;
-
-<p>
- <i>/* identification of switch (for driver) */</i>
-
-<p>
- unsigned char name[32];
-
-<p>
- <i>/* type of switch value ¯ See SND_CTL_SW_TYPE_XXXX */</i>
-
-<p>
- unsigned int type;
-
-<p>
- <i>/* low range value */</i>
-
-<p>
- unsigned int low;
-
-<p>
- <i>/* high range value */</i>
-
-<p>
- unsigned int high;
-
-<p>
- union {
-
-<p>
- unsigned int enable; <i>/* 0 = off 1 = on */</i>
-
-<p>
- unsigned char data8[32]; <i>/* 8-bit data */</i>
-
-<p>
- unsigned short data16[16]; <i>/* 16-bit data */</i>
-
-<p>
- unsigned int data32[8]; <i>/* 32-bit data */</i>
-
-<p>
- } value;
-
-<p>
- <i>/* reserved for future use ¯ must be zero !!! */</i>
-
-<p>
- unsigned char reserved[32];
-
-<p>
-}
-</DL>
-<p>
-
-<H4>int snd_mixer_switch_write(void *handle int switchn snd_mixer_switch_t
-*data)</H4>
-
-<p>
-Writes the <i>*data</i> structure with data about switch with index <i>switchn</i>
-to kernel. Function returns zero if successful, otherwise it returns an error
-code.
-
-<p>
-
-<H4>int snd_mixer_exact_mode(void *handle, int enable)</H4>
-
-<p>
-Turns on = 1 or off = 0 (by default) exact mode. This mode allows application
-to set/get volume values in exact range which uses hardware. In non-exact mode
-range is always from percentage 0 to 100 and driver does conversion to hardware
-range. Function returns zero if successful, otherwise it returns an error code.
-
-<p>
-
-<H4>int snd_mixer_channel(void *handle, const char *channel_id)</H4>
-
-<p>
-Returns the channel number (index) associated with <i>channel_id</i> (channel
-name), or returns an error code. Note: Below mixer channel IDs are subject to
-change and will be extended if new hardware has support for other mixer input/output
-channels.
-
-<p>
-
-<DL compact> <dt><b></b></dt>
- <dd>
-#define SND_MIXER_ID_MASTER "Master"
-
-<p>
-#define SND_MIXER_ID_MASTER1 "Master 1"
-
-<p>
-<i>/* digital master */</i>
-
-<p>
-#define SND_MIXER_ID_MASTERD "Master D"
-
-<p>
-<i>/* second digital master */</i>
-
-<p>
-#define SND_MIXER_ID_MASTERD1 "Master D1"
-
-<p>
-#define SND_MIXER_ID_HEADPHONE "Headphone"
-
-<p>
-#define SND_MIXER_ID_MASTER_MONO "Master M"
-
-<p>
-#define SND_MIXER_ID_3D "3D Wide"
-
-<p>
-#define SND_MIXER_ID_3D_VOLUME "3D Volume"
-
-<p>
-#define SND_MIXER_ID_3D_CENTER "3D Center"
-
-<p>
-#define SND_MIXER_ID_3D_SPACE "3D Space"
-
-<p>
-#define SND_MIXER_ID_3D_DEPTH "3D Depth"
-
-<p>
-#define SND_MIXER_ID_BASS "Bass"
-
-<p>
-#define SND_MIXER_ID_TREBLE "Treble"
-
-<p>
-#define SND_MIXER_ID_FADER "Fader"
-
-<p>
-#define SND_MIXER_ID_SYNTHESIZER "Synth"
-
-<p>
-#define SND_MIXER_ID_SYNTHESIZER1 "Synth 1"
-
-<p>
-#define SND_MIXER_ID_FM "FM"
-
-<p>
-#define SND_MIXER_ID_EFFECT "Effect"
-
-<p>
-#define SND_MIXER_ID_DSP "DSP"
-
-<p>
-#define SND_MIXER_ID_PCM "PCM"
-
-<p>
-#define SND_MIXER_ID_PCM1 "PCM 1"
-
-<p>
-#define SND_MIXER_ID_LINE "Line-In"
-
-<p>
-#define SND_MIXER_ID_MIC "MIC"
-
-<p>
-#define SND_MIXER_ID_CD "CD"
-
-<p>
-#define SND_MIXER_ID_VIDEO "Video"
-
-<p>
-#define SND_MIXER_ID_PHONE "Phone"
-
-<p>
-#define SND_MIXER_ID_GAIN "Record-Gain"
-
-<p>
-#define SND_MIXER_ID_MIC_GAIN "Mic-Gain"
-
-<p>
-#define SND_MIXER_ID_IGAIN "In-Gain"
-
-<p>
-#define SND_MIXER_ID_OGAIN "Out-Gain"
-
-<p>
-#define SND_MIXER_ID_LOOPBACK "Loopback"
-
-<p>
-#define SND_MIXER_ID_SPEAKER "PC Speaker"
-
-<p>
-#define SND_MIXER_ID_MONO "Mono"
-
-<p>
-#define SND_MIXER_ID_MONO1 "Mono 1"
-
-<p>
-#define SND_MIXER_ID_MONO2 "Mono 2"
-
-<p>
-#define SND_MIXER_ID_AUXA "Aux A"
-
-<p>
-#define SND_MIXER_ID_AUXB "Aux B"
-
-<p>
-#define SND_MIXER_ID_AUXC "Aux C"
-</DL>
-<p>
-
-<H4>int snd_mixer_channel_info(void *handle, int channel, snd_mixer_channel_info_t
-*info) </H4>
-
-<p>
-Fills the <i>*info</i> structure. The argument <i>channel</i> specifies
-channel (0 to N) for which is the info requested. Function returns zero if successful,
-otherwise it returns an error code.
-
-<p>
-
-<DL compact> <dt><b></b></dt>
- <dd>
-<i>/* mixer channel is record source */</i>
-
-<p>
-#define SND_MIXER_CINFO_CAP_RECORD 0x00000001
-
-<p>
-<i>/* mixer channel is stereo */</i>
-
-<p>
-#define SND_MIXER_CINFO_CAP_STEREO 0x00000002
-
-<p>
-<i>/* always set at this moment driver emulates mute */</i>
-
-<p>
-#define SND_MIXER_CINFO_CAP_MUTE 0x00000004
-
-<p>
-<i>/* channel supports hardware mute */</i>
-
-<p>
-#define SND_MIXER_CINFO_CAP_HWMUTE 0x00000008
-
-<p>
-<i>/* channel does digital (not analog) mixing */</i>
-
-<p>
-#define SND_MIXER_CINFO_CAP_DIGITAL 0x00000010
-
-<p>
-<i>/* external input channel */</i>
-
-<p>
-#define SND_MIXER_CINFO_CAP_INPUT 0x00000020
-
-<p>
-<i>/* join mute is supported only */</i>
-
-<p>
-<i>/* left and right channel doesn't have separate mute control */</i>
-
-<p>
-#define SND_MIXER_CINFO_CAP_JOINMUTE 0x00000040
-
-<p>
-<i>/* join record is supported only *</i>
-
-<p>
-<i>/* left and right channel doesn't have separate record control */</i>
-
-<p>
-#define SND_MIXER_CINFO_CAP_JOINRECORD 0x00000080
-
-<p>
-<i>/* route left input to right output is supported */</i>
-
-<p>
-#define SND_MIXER_CINFO_CAP_LTOR_OUT 0x00000100
-
-<p>
-<i>/* route right input to left output is supported */</i>
-
-<p>
-#define SND_MIXER_CINFO_CAP_RTOL_OUT 0x00000200
-
-<p>
-<i>/* route left input to right ADC is supported */</i>
-
-<p>
-#define SND_MIXER_CINFO_CAP_LTOR_IN 0x00000400
-
-<p>
-<i>/* route right input to left ADC is supported */</i>
-
-<p>
-#define SND_MIXER_CINFO_CAP_RTOL_IN 0x00000800
-
-<p>
-<i>/* output route is only switch (cannot be used separately) */</i>
-
-<p>
-#define SND_MIXER_CINFO_CAP_SWITCH_OUT 0x00001000
-
-<p>
-<i>/* input route is only switch (cannot be used separately) */</i>
-
-<p>
-#define SND_MIXER_CINFO_CAP_SWITCH_IN 0x00002000
-
-<p>
-<i>/* data can be recorded even if output path is muted */</i>
-
-<p>
-<i>/* (to avoid loopback) */</i>
-
-<p>
-#define SND_MIXER_CINFO_CAP_RECORDBYMUTE 0x00004000
-</DL>
-<p>
-
-
-<p>
-
-<DL compact> <dt><b></b></dt>
- <dd>
-struct snd_mixer_channel_info {
-
-<p>
-<i> /* channel index (filled by application) */</i>
-
-<p>
- unsigned int channel;
-
-<p>
-<i> /* parent channel # or SND_MIXER_PARENT */</i>
-
-<p>
- unsigned int parent;
-
-<p>
-<i> /* name of this device */</i>
-
-<p>
- unsigned char name[12];
-
-<p>
-<i> /* some flags about this device (SND_MIXER_CINFO_XXXX) */</i>
-
-<p>
- unsigned int caps;
-
-<p>
-<i> /* min. value when exact mode (or always 0) */</i>
-
-<p>
- int min;
-
-<p>
-<i> /* max. value when exact mode (or always 100) */ </i>
-
-<p>
- int max;
-
-<p>
-<i> /* minimum decibel value (*100) */</i>
-
-<p>
- int min_dB;
-
-<p>
-<i> /* maximum decibel value (*100) */</i>
-
-<p>
- int max_dB;
-
-<p>
-<i> /* step decibel value (*100) */</i>
-
-<p>
- int step_dB;
-
-<p>
-<i> /* reserved for future use */</i>
-
-<p>
- unsigned char reserved[16];
-
-<p>
-};
-</DL>
-<p>
-
-<H4>int snd_mixer_channel_read(void *handle, int channel, snd_mixer_channel_t
-*data) </H4>
-
-<p>
-Fills the <i>*data</i> structure. The argument <i>channel</i> specifies
-the channel (0 to N) for which is data requested. Function returns zero if successful,
-otherwise it returns an error code.
-
-<p>
-
-<DL compact> <dt><b></b></dt>
- <dd>
-/* channel record source flags */
-
-<p>
-#define SND_MIXER_FLG_RECORD_LEFT 0x00000001
-
-<p>
-#define SND_MIXER_FLG_RECORD_RIGHT 0x00000002
-
-<p>
-#define SND_MIXER_FLG_RECORD 0x00000003
-
-<p>
-/* mute channel flags */
-
-<p>
-#define SND_MIXER_FLG_MUTE_LEFT 0x00010000
-
-<p>
-#define SND_MIXER_FLG_MUTE_RIGHT 0x00020000
-
-<p>
-#define SND_MIXER_FLG_MUTE 0x00030000
-
-<p>
-/* input to output route setup */
-
-<p>
-#define SND_MIXER_FLG_LTOR_OUT 0x00100000
-
-<p>
-#define SND_MIXER_FLG_RTOL_OUT 0x00200000
-
-<p>
-#define SND_MIXER_FLG_SWITCH_OUT 0x00300000
-
-<p>
-/* input to ADC route setup */
-
-<p>
-#define SND_MIXER_FLG_LTOR_IN 0x00400000
-
-<p>
-#define SND_MIXER_FLG_RTOL_IN 0x00800000
-
-<p>
-#define SND_MIXER_FLG_SWITCH_IN 0x00c00000
-
-<p>
-/* set volume in decibels from dB variables */
-
-<p>
-#define SND_MIXER_FLG_DECIBEL 0x40000000
-
-<p>
-/* reserved for kernel use, don't use this flag from application */
-
-<p>
-#define SND_MIXER_FLG_FORCE 0x80000000
-</DL>
-<p>
-
-
-<p>
-
-<DL compact> <dt><b></b></dt>
- <dd>
-struct snd_mixer_channel {
-
-<p>
- /* channel # (filled by application) */
-
-<p>
- unsigned int channel;
-
-<p>
- /* some flags to read/write (SND_MIXER_FLG_XXXX) */
-
-<p>
- unsigned int flags;
-
-<p>
- /* min - max when exact mode (or 0 - 100) */
-
-<p>
- int left;
-
-<p>
- /* min - max when exact mode (or 0 - 100) */
-
-<p>
- int right;
-
-<p>
- /* dB * 100 */
-
-<p>
- int left_dB;
-
-<p>
- /* dB * 100 */
-
-<p>
- int right_dB;
-
-<p>
- unsigned char reserved[16];
-
-<p>
-};
-</DL>
-<p>
-
-<H4>int snd_mixer_channel_write(void *handle, int channel, snd_mixer_channel_t
-*data)</H4>
-
-<p>
-Writes the <i>*data</i> structure to kernel. The <i>channel</i> argument
-specifies the channel (0 to N) for which is data is to be applied. Function
-returns zero if successful, otherwise it returns an error code. This functions
-is the opposite of <i>snd_mixer_channel_read</i>.
-
-<p>
-
-<H4>int snd_mixer_read(void *handle, snd_mixer_callbacks_t *callbacks)</H4>
-
-<p>
-This function reads and parses data from driver. Parsed actions are returned
-back to the application using the <i>callbacks</i> structure. Applications
-should not parse data from the driver in standard cases. This function returns
-immediately after all data is read from driver. Does not block process.
-
-<p>
-
-<DL compact> <dt><b></b></dt>
- <dd>
-typedef struct snd_mixer_callbacks {
-
-<p>
- /* should be used by application */
-
-<p>
- void *private_data;
-
-<p>
- void (*channel_was_changed)(void *private_data, int channel);
-
-<p>
- void (*switch_was_changed)(void *private_data, int switchn);
-
-<p>
- /* reserved for future use - must be NULL!!! */
-
-<p>
- void *reserved[14];
-
-<p>
-} snd_mixer_callbacks_t;
-</DL>
-<p>
- <H4><A NAME="tth_sEc4.1.1">
-4.1.1</A> Examples</H4>
-
-<p>
-The following example shows installed mixer channels for sound card #0 and
-mixer device #0 in the system, and also sets the master volume (if present)
-to 50.
-
-<p>
-
-<DL compact> <dt><b></b></dt>
- <dd>
-int card = 0, device = 0, err;
-
-<p>
-void *handle;
-
-<p>
-snd_mixer_info_t info;
-
-<p>
-snd_mixer_channel_t channel;
-</DL>
-<p>
-
-
-<p>
-
-<DL compact> <dt><b></b></dt>
- <dd>
-if ((err = snd_mixer_open(&handle, card, device)) < 0) {
-
-<p>
- fprintf(stderr, "open failed: %s\n", snd_strerror(err));
-
-<p>
- return;
-
-<p>
-}
-
-<p>
-if ((err = snd_mixer_info(handle, &info)) < 0) {
-
-<p>
- fprintf(stderr, "info failed: %s\n", snd_strerror(err));
-
-<p>
- snd_mixer_close(handle);
-
-<p>
- return;
-
-<p>
-}
-
-<p>
-printf("Installed MIXER channels for card #i and device %i: %i\n", card + 1, device,
-
-<p>
- info.channels);
-
-<p>
-master = snd_mixer_channel(handle, SND_MIXER_ID_MASTER);
-
-<p>
-if (master >= 0) {
-
-<p>
- if ((err = snd_mixer_read(handle, master, &channel)) < 0) { fprintf(stderr, "master read failed: %s\n", snd_strerror( err ));
-
-<p>
- snd_mixer_close( handle );
-
-<p>
- return;
-
-<p>
- }
-
-<p>
- channel.left = channel.right = 50;
-
-<p>
- if ((err = snd_mixer_write(handle, master, &channel)) < 0 ) { fprintf(stderr, "master write failed: %s\n", snd_strerror( err ));
-
-<p>
- snd_mixer_close(handle);
-
-<p>
- return;
-
-<p>
- }
-
-<p>
-}
-
-<p>
-snd_mixer_close(handle);
-</DL>
-<p>
- <H2><A NAME="tth_sEc5">
-5</A> Digital Audio (PCM) Interface</H2>
-
-<p>
-Digital audio is the most commonly used method of representing sound inside
-a computer. In this method sound is stored as a sequence of samples taken from
-the audio signal using constant time intervals. A sample represents volume of
-the signal at the moment when it was measured. In uncompressed digital audio
-each sample require one or more bytes of storage. The number of bytes required
-depends on number of channels (mono, stereo) and sample format (8 or 16 bits,
-mu-Law, etc.). The length of this interval determines the sampling rate. Commonly
-used sampling rates are between 8 kHz (telephone quality) and 48 kHz (DAT tapes).
-
-<p>
-The physical devices used in digital audio are called the ADC (Analog to Digital
-Converter) and DAC (Digital to Analog Converter). A device containing both ADC
-and DAC is commonly known as a codec. The codec device used in a Sound Blaster
-cards is called a DSP which is somewhat misleading since DSP also stands for
-Digital Signal Processor (the SB DSP chip is very limited when compared to "true"
-DSP chips).
-
-<p>
-Sampling parameters affect the quality of sound which can be reproduced from
-the recorded signal. The most fundamental parameter is sampling rate which limits
-the highest frequency that can be stored. It is well known (Nyquist's Sampling
-Theorem) that the highest frequency that can be stored in a sampled signal is
-at most 1/2 of the sampling frequency. For example, an 8 kHz sampling rate permits
-the recording of a signal in which the highest frequency is less than 4 kHz.
-Higher frequency signals must be filtered out before feeding them to DAC.
-
-<p>
-Sample encoding limits the dynamic range of a recorded signal (difference between
-the faintest and the loudest signal that can be recorded). In theory the maximum
-dynamic range of signal is number_of_bits * 6 dB . This means that 8 bits
-sampling resolution gives dynamic range of 48 dB and 16 bit resolution gives
-96 dB.
-
-<p>
-Quality has price. The number of bytes required to store an audio sequence depends
-on sampling rate, number of channels and sampling resolution. For example just
-8000 bytes of memory is required to store one second of sound using 8 kHz/8
-bits/mono but 48 kHz/16bit/stereo takes 192 kilobytes. A 64 kbps ISDN channel
-is required to transfer a 8kHz/8bit/mono audio stream in real time, and about
-1.5 Mbps is required for DAT quality (48kHz/16bit/stereo). On the other hand
-it is possible to store just 5.46 seconds of sound in a megabyte of memory when
-using 48kHz/16bit/stereo sampling. With 8kHz/8bits/mono it is possible to store
-131 seconds of sound using the same amount of memory. It is possible to reduce
-memory and communication costs by compressing the recorded signal but this is
-beyond the scope of this document.
-
-<p>
- <H3><A NAME="tth_sEc5.1">
-5.1</A> Low-Level Layer</H3>
-
-<p>
-Audio devices are opened exclusively for a selected direction. This doesn't
-allow open from more than one processes for the same audio device in the same
-direction, but does allow one open call to each playback direction and second
-open call to record direction independently. Audio devices return EBUSY error
-to applications when other applications have already opened the requested direction.
-
-<p>
-Low-Level layer supports these formats:
-
-<p>
-
-<DL compact> <dt><b></b></dt>
- <dd>
-<i>/* muLaw compressed samples */</i>
-
-<p>
-#define SND_PCM_SFMT_MU_LAW 0
-
-<p>
-<i>/* aLaw compressed samples */</i>
-
-<p>
-#define SND_PCM_SFMT_A_LAW 1
-
-<p>
-<i>/* Ima-ADPM 4:1 compressed samples */</i>
-
-<p>
-#define SND_PCM_SFMT_IMA_ADPCM 2
-
-<p>
-<i>/* Unsigned 8-bit samples (most common 8-bit format) */</i>
-
-<p>
-#define SND_PCM_SFMT_U8 3
-
-<p>
-<i>/* Signed 16-bit Little Endian samples (most common 16-bit format) */</i>
-
-<p>
-#define SND_PCM_SFMT_S16_LE 4
-
-<p>
-<i>/* Signed 16-bit Big Endian samples */</i>
-
-<p>
-#define SND_PCM_SFMT_S16_BE 5
-
-<p>
-<i>/* Signed 8-bit samples */</i>
-
-<p>
-#define SND_PCM_SFMT_S8 6
-
-<p>
-<i>/* Unsigned 16-bit Little Endian samples */</i>
-
-<p>
-#define SND_PCM_SFMT_U16_LE 7
-
-<p>
-<i>/* Unsigned 16-bit Big Endian samples */</i>
-
-<p>
-#define SND_PCM_SFMT_U16_BE 8
-
-<p>
-<i>/* MPEG 1/2 stream */</i>
-
-<p>
-#define SND_PCM_SFMT_MPEG 9
-
-<p>
-<i>/* GSM stream */</i>
-
-<p>
-#define SND_PCM_SFMT_GSM 10
-</DL>
-<p>
-
-
-<p>
-
-<DL compact> <dt><b></b></dt>
- <dd>
-#define SND_PCM_FMT_MU_LAW (1 << SND_PCM_SFMT_MU_LAW)
-
-<p>
-#define SND_PCM_FMT_A_LAW (1 << SND_PCM_SFMT_A_LAW)
-
-<p>
-#define SND_PCM_FMT_IMA_ADPCM (1 << SND_PCM_SFMT_IMA_ADPCM)
-
-<p>
-#define SND_PCM_FMT_U8 (1 << SND_PCM_SFMT_U8)
-
-<p>
-#define SND_PCM_FMT_S16_LE (1 << SND_PCM_SFMT_S16_LE)
-
-<p>
-#define SND_PCM_FMT_S16_BE (1 << SND_PCM_SFMT_S16_BE)
-
-<p>
-#define SND_PCM_FMT_S8 (1 << SND_PCM_SFMT_S8)
-
-<p>
-#define SND_PCM_FMT_U16_LE (1 << SND_PCM_SFMT_U16_LE)
-
-<p>
-#define SND_PCM_FMT_U16_BE (1 << SND_PCM_SFMT_U16_BE)
-
-<p>
-#define SND_PCM_FMT_MPEG (1 << SND_PCM_SFMT_MPEG)
-
-<p>
-#define SND_PCM_FMT_GSM (1 << SND_PCM_SFMT_GSM)
-</DL>
-<p>
-Constants with prefix <i>SND_PCM_FMT_</i> are used in info structures and
-constants with prefix <i>SND_PCM_SFMT_</i> are used in format structures.
-
-<p>
-ALSA PCM API uses an enhanced double buffering scheme. This allows the user
-to implement a more comfortable buffer setup. Audio buffer is separated to small
-fragments. Each fragment has the same size. Application can set wakeup limits
-like ``I want to get recorded data when at least two fragments with size 160
-bytes are filled.''. For more information you should see description of <i>snd_pcm_*_params_t</i>
-and <i>snd_pcm_*_status_t</i> structures and the <em>snd_pcm_playback_status(),
-snd_pcm_record_status()</em> functions, documented below.
-
-<p>
-
-<H4>int snd_pcm_open(void **handle, int card, int device, int mode)</H4>
-
-<p>
-Creates a new handle and opens a connection to the kernel sound audio interface
-for sound card number <i>card</i> (0-N) and audio device number <i>device</i>.
-Function also checks if protocol is compatible to prevent use of old programs
-with a new kernel API. Function returns zero if successful otherwise it returns
-an error code. Error code -EBUSY is returned when some process owns the selected
-direction.
-
-<p>
-Default format after opening is mono <i>mu-Law</i> at 8000Hz. This device
-can be used directly for playback of standard .au (Sparc) files.
-
-<p>
-The following modes should be used for the <i>mode</i> argument:
-
-<p>
-
-<DL compact> <dt><b></b></dt>
- <dd>
-#define SND_PCM_OPEN_PLAYBACK (O_WRONLY)
-
-<p>
-#define SND_PCM_OPEN_RECORD (O_RDONLY)
-
-<p>
-#define SND_PCM_OPEN_DUPLEX (O_RDWR)
-</DL>
-<p>
-
-<H4>int snd_pcm_close(void *handle)</H4>
-
-<p>
-Frees all resources allocated with audio handle and closes the connection to
-the kernel sound audio interface. Function returns zero if successful, otherwise
-it returns an error code.
-
-<p>
-
-<H4>int snd_pcm_file_descriptor(void *handle)</H4>
-
-<p>
-Returns the file descriptor of the connection to the kernel sound audio interface.
-Function returns an error code if an error was encountered.
-
-<p>
-The file descriptor should be used for the <i>select(2)</i> synchronous multiplexer
-function for setting the read direction. Application should call <i>snd_pcm_read()</i>
-or <i>snd_pcm_write()</i> functions if data is waiting to be read or a write
-can be performed. Calling these functions is highly recommended, as it leaves
-a place for the API to do things like data conversions, if needed.
-
-<p>
-
-<H4>int snd_pcm_block_mode(void *handle, int enable) </H4>
-
-<p>
-Sets up block (default) or non-block mode for a handle. Block mode suspends
-execution of a program when <i>snd_pcm_read()</i> or <i>snd_pcm_write()</i>
-is called for the time which is needed for the actual playback or record over
-of the selected limit. In non-block mode, programs aren't suspended and the
-above functions return immediately with the count of bytes which were read or
-written by the driver. When used in this way, don't try to use the entire buffer
-after the call, but instead process the number of bytes returned, and call the
-function again.
-
-<p>
-
-<H4>int snd_pcm_info(void *handle, snd_pcm_info_t *info)</H4>
-
-<p>
-Fills the <i>*info</i> structure with data about the PCM device selected
-by <i>*handle</i>. Function returns zero if successful, otherwise it returns
-an error code.
-
-<p>
-
-<DL compact> <dt><b></b></dt>
- <dd>
-<i>/* hardware have codec */</i>
-
-<p>
-#define SND_PCM_INFO_CODEC 0x00000001
-
-<p>
-#define SND_PCM_INFO_DSP SND_PCM_INFO_CODEC
-
-<p>
-<i>/* this flag is reserved and should be never used */</i>
-
-<p>
-<i>/* It remains for compatibility with Open Sound System driver. */</i>
-
-<p>
-#define SND_PCM_INFO_MMAP 0x00000002
-
-<p>
-<i>/* playback direction is supported */</i>
-
-<p>
-#define SND_PCM_INFO_PLAYBACK 0x00000100
-
-<p>
-<i>/* record direction is supported */</i>
-
-<p>
-#define SND_PCM_INFO_RECORD 0x00000200
-
-<p>
-#define SND_PCM_INFO_DUPLEX 0x00000400
-
-<p>
-<i>/* rate for playback & record must be same */</i>
-
-<p>
-#define SND_PCM_INFO_DUPLEX_LIMIT 0x00000800
-
-<p>
-<i>/* duplex is supported only by mono (one channel) format */</i>
-
-<p>
-#define SND_PCM_INFO_DUPLEX_MONO 0x00001000
-</DL>
-<p>
-
-
-<p>
-
-<DL compact> <dt><b></b></dt>
- <dd>
-struct snd_pcm_info {
-
-<p>
-<i> /* sound card type */</i>
-
-<p>
- unsigned int type;
-
-<p>
-<i> /* see SND_PCM_INFO_XXXX */</i>
-
-<p>
- unsigned int flags;
-
-<p>
-<i> /* ID of this PCM device */</i>
-
-<p>
- unsigned char id[32];
-
-<p>
-<i> /* name of this device */</i>
-
-<p>
- unsigned char name[80];
-
-<p>
-<i> /* reserved for future use */</i>
-
-<p>
- unsigned char reserved[64];
-
-<p>
-};
-</DL>
-<p>
-
-<H4>int snd_pcm_playback_info(void *handle, snd_pcm_playback_info_t *info)</H4>
-
-<p>
-Fills the *info structure with data about PCM playback. Function returns zero
-if successful, otherwise it returns an error code.
-
-<p>
-
-<DL compact> <dt><b></b></dt>
- <dd>
-#define SND_PCM_PINFO_BATCH 0x00000001
-
-<p>
-#define SND_PCM_PINFO_8BITONLY 0x00000002
-
-<p>
-#define SND_PCM_PINFO_16BITONLY 0x00000004
-</DL>
-<p>
-
-
-<p>
-
-<DL compact> <dt><b></b></dt>
- <dd>
-struct snd_pcm_playback_info {
-
-<p>
-<i> /* see SND_PCM_PINFO_XXXX */</i>
-
-<p>
- unsigned int flags;
-
-<p>
-<i> /* supported formats */ </i>
-
-<p>
- unsigned int formats;
-
-<p>
-<i> /* min rate (in Hz) */ </i>
-
-<p>
- unsigned int min_rate;
-
-<p>
-<i> /* max rate (in Hz) */ </i>
-
-<p>
- unsigned int max_rate;
-
-<p>
-<i> /* min channels - voices (probably always 1) */ </i>
-
-<p>
- unsigned int min_channels;
-
-<p>
-<i> /* max channels - voices */ </i>
-
-<p>
- unsigned int max_channels;
-
-<p>
-<i> /* playback buffer size in bytes */</i>
-
-<p>
- unsigned int buffer_size;
-
-<p>
-<i> /* min fragment size in bytes */ </i>
-
-<p>
- unsigned int min_fragment_size;
-
-<p>
-<i> /* max fragment size in bytes */</i>
-
-<p>
- unsigned int max_fragment_size;
-
-<p>
-<i> /* align fragment value */</i>
-
-<p>
- unsigned int fragment_align;
-
-<p>
-<i> /* supported formats directly by hardware */</i>
-
-<p>
- unsigned int hw_formats;
-
-<p>
-<i> /* count of playback switches */</i>
-
-<p>
- unsigned int switches;
-
-<p>
-<i> /* reserved for future use */</i>
-
-<p>
- unsigned char reserved[56];
-
-<p>
-};
-</DL>
-<p>
-
-<DL compact><dt><b></b></dt>
- <dd> [SND_PCM_PINFO_BATCH]Driver implements double buffering with this device.
-This means that the chip used for data processing has its own memory, and output
-will be more delayed than if a traditional codec chip is used.
-<dt><b></b></dt>
- <dd> [SND_PCM_PINFO_8BITONLY]If this bit is set, the driver uses 8-bit format
-for 16-bit samples and does software conversion. This bit is set on broken SoundBlaster
-16/AWE sound cards which can't do full 16-bit duplex. If this bit is set application
-or higher digital audio layer should do the conversion from 16-bit samples to
-8-bit samples rather than making the driver to do it in the kernel.
-<dt><b></b></dt>
- <dd> [SND_PCM_PINFO_16BITONLY]If this bit is set, driver uses 16-bit format for
-8-bit samples and does software conversion. This bit is set on broken SoundBlaster
-16/AWE sound cards which can't do full 8-bit duplex. If this bit is set the
-application or higher digital audio layer should do conversion from 8-bit samples
-to 16-bit samples rather than making the driver to do it in the kernel.
-</DL>
-<p>
-
-<H4>int snd_pcm_record_info(void *handle, snd_pcm_record_info_t *info)</H4>
-
-<p>
-Fills the *info structure. Returns zero if successful, otherwise it returns
-an error code.
-
-<p>
-
-<DL compact> <dt><b></b></dt>
- <dd>
-#define SND_PCM_RINFO_BATCH 0x00000001
-
-<p>
-#define SND_PCM_RINFO_8BITONLY 0x00000002
-
-<p>
-#define SND_PCM_RINFO_16BITONLY 0x00000004
-
-<p>
-#define SND_PCM_RINFO_OVERRANGE 0x00001000
-</DL>
-<p>
-
-
-<p>
-
-<DL compact> <dt><b></b></dt>
- <dd>
-struct snd_pcm_record_info {
-
-<p>
-<i> /* see SND_PCM_RINFO_XXXX */</i>
-
-<p>
- unsigned int flags;
-
-<p>
-<i> /* supported formats */ </i>
-
-<p>
- unsigned int formats;
-
-<p>
-<i> /* min rate (in Hz) */ </i>
-
-<p>
- unsigned int min_rate;
-
-<p>
-<i> /* max rate (in Hz) */ </i>
-
-<p>
- unsigned int max_rate;
-
-<p>
-<i> /* min channels - voices (probably always 1) */ </i>
-
-<p>
- unsigned int min_channels;
-
-<p>
-<i> /* max channels - voices */ </i>
-
-<p>
- unsigned int max_channels;
-
-<p>
-<i> /* playback buffer size in bytes */</i>
-
-<p>
- unsigned int buffer_size;
-
-<p>
-<i> /* min fragment size in bytes */ </i>
-
-<p>
- unsigned int min_fragment_size;
-
-<p>
-<i> /* max fragment size in bytes */</i>
-
-<p>
- unsigned int max_fragment_size;
-
-<p>
-<i> /* align fragment value */</i>
-
-<p>
- unsigned int fragment_align;
-
-<p>
-<i> /* supported formats directly by hardware */</i>
-
-<p>
- unsigned int hw_formats;
-
-<p>
-<i> /* count of record switches */</i>
-
-<p>
- unsigned int switches;
-
-<p>
-<i> /* reserved for future use */</i>
-
-<p>
- unsigned char reserved[56];
-
-<p>
-};
-</DL>
-<p>
-
-<DL compact><dt><b></b></dt>
- <dd> [SND_PCM_RINFO_BATCH]Driver implements double buffering with this device.
-This means that the chip used for data processing has its own memory, and input
-will be more delayed than if a traditional codec chip is used.
-<dt><b></b></dt>
- <dd> [SND_PCM_RINFO_8BITONLY]If this bit is set, the driver uses 8-bit format
-for 16-bit samples and does software conversion. This bit is set on broken SoundBlaster
-16/AWE sound cards which can't do full 16-bit duplex. If this bit is set application
-or higher digital audio layer should do the conversion from 16-bit samples to
-8-bit samples rather than making the driver to do it in the kernel.
-<dt><b></b></dt>
- <dd> [SND_PCM_RINFO_16BITONLY]If this bit is set, driver uses 16-bit format for
-8-bit samples and does software conversion. This bit is set on broken SoundBlaster
-16/AWE sound cards which can't do full 8-bit duplex. If this bit is set the
-application or higher digital audio layer should do conversion from 8-bit samples
-to 16-bit samples rather than making the driver to do it in the kernel.
-<dt><b></b></dt>
- <dd> [SND_PCM_RINFO_OVERRANGE]If this bit is set the hardware can do ADC
-over-range detection.
-</DL>
-<p>
-
-<H4>int snd_pcm_playback_switches(void *handle)</H4>
-
-<p>
-Returns count of PCM playback switches. In this contents switch means universal
-control interface between kernel and application which allows variable type
-control. Function returns count if successful, otherwise it returns an error
-code. Return value should be zero if sound card doesn't have any PCM playback
-switch.
-
-<p>
-
-<H4>int snd_pcm_playback_switch(void *handle, const char *switch_id)</H4>
-
-<p>
-Returns index for switch with name <i>switch_id</i>. Function returns switch
-index if successful, otherwise it returns an error code.
-
-<p>
-
-<H4>int snd_pcm_playback_switch_read(void *handle int switchnsnd_pcm_switch_t *data)</H4>
-
-<p>
-Fills the <i>*data</i> structure with data about switch with index <i>switchn</i>.
-Function returns zero if successful, otherwise it returns an error code.
-
-<p>
-
-<DL compact> <dt><b></b></dt>
- <dd>
-<i>/* 0 or 1 (enable member of union) */</i>
-
-<p>
-#define SND_PCM_SW_TYPE_BOOLEAN 0
-
-<p>
-<i>/* 0 to 255 - from low to high (data8[0] member of union) */</i>
-
-<p>
-#define SND_PCM_SW_TYPE_BYTE 1
-
-<p>
-<i>/* 0 to 65535 - from low to high (data16[0] member of union) */</i>
-
-<p>
-#define SND_PCM_SW_TYPE_WORD 2
-
-<p>
-<i>/* 0 to 4294967296 ¯ from low to high (data32[0] member of union) */</i>
-
-<p>
-#define SND_PCM_SW_TYPE_DWORD 3
-
-<p>
-<i>/* user type - no type control */</i>
-
-<p>
-#define SND_PCM_SW_TYPE_USER (~0)
-</DL>
-<p>
-
-
-<p>
-
-<DL compact> <dt><b></b></dt>
- <dd>
-struct snd_pcm_switch {
-
-<p>
- <i>/* switch index (filled by application) */</i>
-
-<p>
- unsigned int switchn;
-
-<p>
- <i>/* identification of switch (for driver) */</i>
-
-<p>
- unsigned char name[32];
-
-<p>
- <i>/* type of switch value ¯ See SND_PCM_SW_TYPE_XXXX */</i>
-
-<p>
- unsigned int type;
-
-<p>
- <i>/* low range value */</i>
-
-<p>
- unsigned int low;
-
-<p>
- <i>/* high range value */</i>
-
-<p>
- unsigned int high;
-
-<p>
- union {
-
-<p>
- unsigned int enable; <i>/* 0 = off 1 = on */</i>
-
-<p>
- unsigned char data8[32]; <i>/* 8-bit data */</i>
-
-<p>
- unsigned short data16[16]; <i>/* 16-bit data */</i>
-
-<p>
- unsigned int data32[8]; <i>/* 32-bit data */</i>
-
-<p>
- } value;
-
-<p>
- <i>/* reserved for future use ¯ must be zero !!! */</i>
-
-<p>
- unsigned char reserved[32];
-
-<p>
-}
-</DL>
-<p>
-
-<H4>int snd_pcm_playback_switch_write(void *handle int switchnsnd_pcm_switch_t *data)</H4>
-
-<p>
-Writes the <i>*data</i> structure with data about switch with index <i>switchn</i>
-to kernel. Function returns zero if successful, otherwise it returns an error
-code.
-
-<p>
-
-<H4>int snd_pcm_record_switches(void *handle)</H4>
-
-<p>
-Returns count of PCM record switches. In this context 'switch' means universal
-control interface between kernel and application which allows various types
-of control. Function returns count if successful, otherwise it returns an error
-code. Return value should be zero if sound card doesn't have any PCM record
-switch.
-
-<p>
-
-<H4>int snd_pcm_record_switch(void *handle, const char *switch_id)</H4>
-
-<p>
-Returns index for switch with name <i>switch_id</i>. Function returns switch
-index if successful, otherwise it returns an error code.
-
-<p>
-
-<H4>int snd_pcm_record_switch_read(void *handle int switchn snd_pcm_switch_t
-*data)</H4>
-
-<p>
-Fills the <i>*data</i> structure with data about switch with index <i>switchn</i>.
-Function returns zero if successful, otherwise it returns an error code.
-
-<p>
-
-<H4>int snd_pcm_record_switch_write(void *handle int switchnsnd_pcm_switch_t *data)</H4>
-
-<p>
-Writes the <i>*data</i> structure with data about switch with index <i>switchn</i>
-to kernel. Function returns zero if successful, otherwise it returns an error
-code.
-
-<p>
-
-<H4>int snd_pcm_playback_format(void *handle, snd_pcm_format_t *format)</H4>
-
-<p>
-Sets up format, rate (in Hz) and number of channels for playback, in the desired
-direction. Function returns zero if successful, otherwise it returns an error
-code.
-
-<p>
-
-<DL compact> <dt><b></b></dt>
- <dd>
-struct snd_pcm_format {
-
-<p>
- unsigned int format; <i>/* SND_PCM_SFMT_XXXX */</i>
-
-<p>
- unsigned int rate; <i>/* rate in Hz */</i>
-
-<p>
- unsigned int channels; <i>/* channels (voices) */</i>
-
-<p>
- unsigned char reserved[16];
-
-<p>
-};
-</DL>
-<p>
-
-<H4>int snd_pcm_record_format(void *handle, snd_pcm_format_t *format) </H4>
-
-<p>
-Sets up format, rate (in Hz) and number of channels for used for recording in
-the specified direction. Function returns zero if successful, otherwise it returns
-an error code.
-
-<p>
-
-<DL compact> <dt><b></b></dt>
- <dd>
-struct snd_pcm_format {
-
-<p>
- unsigned int format; <i>/* SND_PCM_SFMT_XXXX */</i>
-
-<p>
- unsigned int rate; <i>/* rate in Hz */</i>
-
-<p>
- unsigned int channels; <i>/* channels (voices) */</i>
-
-<p>
- unsigned char reserved[16];
-
-<p>
-};
-</DL>
-<p>
-
-<H4>int snd_pcm_playback_params(void *handle, snd_pcm_playback_params_t
-*params)</H4>
-
-<p>
-Sets various parameters for playback direction. Function returns zero if successful,
-otherwise it returns an error code.
-
-<p>
-
-<DL compact> <dt><b></b></dt>
- <dd>
-struct snd_pcm_playback_params {
-
-<p>
- int fragment_size;
-
-<p>
- int fragments_max;
-
-<p>
- int fragments_room;
-
-<p>
-<i> /* reserved for future use - must be filled with zero */</i>
-
-<p>
- unsigned char reserved[16];
-
-<p>
-};
-</DL>
-<p>
-
-<DL compact><dt><b></b></dt>
- <dd> [fragment_size]Requested size of fragment. This value should be aligned for
-current format (for example to 4 if stereo 16-bit samples are used) or with
-the <i>fragment_align</i> variable from <i>snd_pcm_playback_info_t</i>
-structure. Its range can be from <i>min_fragment_size</i> to <i>max_fragment_size</i>.
-<dt><b></b></dt>
- <dd> [fragments_max]Maximum number of fragments in queue for wakeup. This number
-doesn't include partly used fragments. If the current count of filled playback
-fragments is greater than this value the driver will block the application or
-return immediately back if non-block mode is active.
-<dt><b></b></dt>
- <dd> [fragments_room]Minimum number of fragments writable for wakeup. This value
-should in most cases be 1 which means return back to application if at least
-one fragment is free for playback. This value includes partly used fragments,
-too.
-</DL>
-<p>
-
-<H4>int snd_pcm_record_params(void *handle, snd_pcm_record_params_t *params)</H4>
-
-<p>
-Function sets various parameters for the recording direction. Function returns
-zero if successful, otherwise it returns an error code.
-
-<p>
-
-<DL compact> <dt><b></b></dt>
- <dd>
-struct snd_pcm_record_params {
-
-<p>
- int fragment_size;
-
-<p>
- int fragments_min;
-
-<p>
-<i> /* reserved for future use - must be filled with zero */</i>
-
-<p>
- unsigned char reserved[16];
-
-<p>
-};
-</DL>
-<p>
-
-<DL compact><dt><b></b></dt>
- <dd> [fragment_size]Requested size of fragment. This value should be aligned for
-current format (for example to 4 if stereo 16-bit samples are used) or set to
-the <i>fragment_align</i> variable from <i>snd_pcm_playback_info_t</i>
-structure. Its range can be from <i>min_fragment_size</i> to <i>max_fragment_size</i>.
-<dt><b></b></dt>
- <dd> [fragments_min]Minimum filled fragments for wakeup. Driver blocks the application
-(if block mode is selected) until input buffer is filled with less than the
-number of fragments specified with this value.
-</DL>
-<p>
-
-<H4>int snd_pcm_playback_status(void *handle, snd_pcm_playback_status_t
-*status)</H4>
-
-<p>
-Fills the <i>*status</i> structure. Function returns zero if successful,
-otherwise it returns an error code.
-
-<p>
-
-<DL compact> <dt><b></b></dt>
- <dd>
-struct snd_pcm_playback_status {
-
-<p>
- unsigned int rate;
-
-<p>
- int fragments;
-
-<p>
- int fragment_size;
-
-<p>
- int count;
-
-<p>
- int queue;
-
-<p>
- int underrun;
-
-<p>
- struct timeval time;
-
-<p>
- struct timeval stime;
-
-<p>
- int scount;
-
-<p>
-<i> /* reserved for future use - must be filled with zero */</i>
-
-<p>
- unsigned char reserved[16];
-
-<p>
-};
-</DL>
-<p>
-
-<DL compact><dt><b></b></dt>
- <dd> [rate]Real playback rate. This value reflects hardware limitations.
-<dt><b></b></dt>
- <dd> [fragments]Currently allocated fragments by the driver for playback direction.
-<dt><b></b></dt>
- <dd> [fragment_size]Current fragment size used by driver for the playback direction.
-<dt><b></b></dt>
- <dd> [count]Count of bytes writable without blocking.
-<dt><b></b></dt>
- <dd> [queue]Count of bytes in queue. Note: <i>(fragments*fragment_size) -
-queue</i> should not be equal to <i>count</i>.
-<dt><b></b></dt>
- <dd> [underrun]This value tells the application the number of underruns since the
-last call to <i>snd_pcm_playback_status</i><em>()</em>.
-<dt><b></b></dt>
- <dd> [time]Estimated time when the next written sample will actually be played (time
-is always in the future). The estimate is calculated with: current time + sample
-queue <em></em>converted to time (number of samples waiting for write to device,
-i.e., the same as the <em>queue</em> member above). This value should be used
-for time synchronization. Returned value is in the same format as returned from
-the standard C function <em>gettimeofday</em>(&<em>time</em>, <em>NULL</em>). This
-variable contains valid information only if playback time mode is enabled (see
-<i>snd_pcm_playback_time()</i> function).
-<dt><b></b></dt>
- <dd> [stime]Time when playback was started. This variable contains valid information
-only if playback time mode is enabled (see <i>snd_pcm_playback_time()</i>
-function).
-<dt><b></b></dt>
- <dd> [scount]Number of bytes processed (actually played) from playback start. This
-number is not necessarily the same as byte count written by application.
-</DL>
-<p>
- <center><img src="pcmbuf.gif">
-<p>
-</center> The figure above shows an example situation in the audio playback buffer in
-the ALSA driver. The driver splits the audio buffer into 16 <em>fragments</em>,
-each being <em>fragment_size</em> bytes long. Fragments 0 and 12-15 are filled
-with samples. Fragment 1 is filled partly (about 75%). Driver is playing and
-current playback position is in fragment 12 (about 35%). As you can seefree space (structure member <i>count</i>) is counted without including the
-fragment which is being played.
-
-<p>
-
-<H4>int snd_pcm_record_status(void *handle, snd_pcm_record_status_t *status)</H4>
-
-<p>
-Fills the <i>*status</i> structure. Function returns zero if successful,
-otherwise it returns an error code.
-
-<p>
-
-<DL compact> <dt><b></b></dt>
- <dd>
-struct snd_pcm_record_status {
-
-<p>
- unsigned int rate;
-
-<p>
- int fragments;
-
-<p>
- int fragment_size;
-
-<p>
- int count;
-
-<p>
- int free;
-
-<p>
- int overrun;
-
-<p>
- struct timeval time;
-
-<p>
- struct timeval stime;
-
-<p>
- int scount;
-
-<p>
- int overrange;
-
-<p>
-<i> /* reserved for future use - must be filled with zero */</i>
-
-<p>
- unsigned char reserved[16];
-
-<p>
-};
-</DL>
-<p>
-
-<DL compact><dt><b></b></dt>
- <dd> [rate]Real record rate. This value reflects hardware limitations.
-<dt><b></b></dt>
- <dd> [fragments]Currently allocated fragments by driver for the record direction.
-<dt><b></b></dt>
- <dd> [fragment_size]Current fragment size used by driver for the record direction.
-<dt><b></b></dt>
- <dd> [count]Count of bytes readable without blocking.
-<dt><b></b></dt>
- <dd> [free]Count of bytes in buffer still free. Note: <i>(fragments*fragment_size)
-- free</i> should not be equal to <i>count</i>.
-<dt><b></b></dt>
- <dd> [overrun]This value tells application the count of overruns since the last call
-to <i>snd_pcm_record_status</i>.
-<dt><b></b></dt>
- <dd> [time]Returns a timestamp for the next sample to be read from the record ring
-buffer (time is always in the past). The timestamp is calculated with: current
-time - sample queue converted to time (waiting for application read() + current
-position in fragment is the same as record count + current position in fragment).
-This value should be used for time synchronization. Returned value is in the
-same format as returned by the standard C function gettimeofday(&time, NULL).
-This variable contains right valid information only if record time mode is enabled
-(see <i>snd_pcm_record_time()</i> function).
-<dt><b></b></dt>
- <dd> [stime]Time when record was started. This variable contains valid information
-only if record time mode is enabled (see <i>snd_pcm_record_time</i> function).
-<dt><b></b></dt>
- <dd> [scount]Number of bytes processed (actually recorded) from record start (stime).
-This number is not necessarily the same as the byte count read by application.
-<dt><b></b></dt>
- <dd> [overrange]ADC overrange count. This value is used only when <i>SND_PCM_RINFO_OVERRANGE</i>
-bit in <i>struct snd_pcm_record_info_t->flags</i> is set (if hardware
-supports this feature).
-</DL>
-<p>
- <center><img src="pcmbuf1.gif">
-<p>
-</center> The figure above shows an example situation in the audio record buffer in the
-ALSA driver. The driver splits the audio buffer into 16 <em>fragments</em>, each
-being <em>fragment_size</em> bytes in length. Fragments 0 and 12-15 are filled
-with samples. Fragment 1 is partly filled (about 75%) and at the end of the
-filled area is the active record position. Data which is ready for the application
-begins in fragment 12 (about 35%). As you can see free space (structure
-member <i>free</i>) is counted without including the fragment which is partly
-filled with samples and the application reads data from this fragment.
-
-<p>
-
-<H4>int snd_pcm_drain_playback(void *handle)</H4>
-
-<p>
-This function stops and drains (destroys) the playback buffers immediately.
-Function returns zero if successful, otherwise it returns an error code.
-
-<p>
-
-<H4>int snd_pcm_flush_playback(void *handle)</H4>
-
-<p>
-This function flushes the playback buffers. It blocks the program while the
-all the waiting samples in kernel playback buffers are processed. Function returns
-zero if successful, otherwise it returns an error code.
-
-<p>
-
-<H4>int snd_pcm_flush_record(void *handle)</H4>
-
-<p>
-This function flushes (destroys) record buffers. Function returns zero if successful,
-otherwise it returns an error code.
-
-<p>
-
-<H4>int snd_pcm_playback_pause(void *handle int enable)</H4>
-
-<p>
-This function pauses playback if <i>enable</i> is non-zero. To restore playing
-mode call this function with <i>enable</i> equal to zero. Function returns
-zero if successful, otherwise it returns an error code.
-
-<p>
-
-<H4>int snd_pcm_playback_time(void *handle, int enable)</H4>
-
-<p>
-This function enables or disables time mode for the playback direction. Time
-mode is useful in synchronizing an application with other events. Function returns
-zero if successful, otherwise it returns an error code.
-
-<p>
-
-<H4>int snd_pcm_record_time(void *handle, int enable)</H4>
-
-<p>
-This function enables or disables time mode for record direction. Time mode
-is useful in synchronizing an application with other events. Function returns
-zero if successful, otherwise it returns an error code.
-
-<p>
-
-<H4>ssize_t snd_pcm_write(void *handle, const void *buffer, size_t size)</H4>
-
-<p>
-Writes samples to the device which must be in the proper format specified by
-the <i>snd_pcm_playback_format</i> function. Function returns zero or positive
-value if playback was successful (value represents count of bytes which were
-successfully written to device) or an error value if an error occurred. Function
-will suspend process if block mode is active.
-
-<p>
-
-<H4>ssize_t snd_pcm_read(void *handle, void *buffer, size_t size)</H4>
-
-<p>
-Function reads samples from driver. Samples are in format specified by <i>snd_pcm_record_format</i>
-function. Function returns zero or positive value if record was success (value
-represents count of bytes which was successfully read from device) or negative
-error value if error occurred. Function will suspend process if block mode is
-active.
-
-<p>
- <H4><A NAME="tth_sEc5.1.1">
-5.1.1</A> Example</H4>
-
-<p>
-The following example shows how to play the first 512kB from the /tmp/test.au
-file with sound card #0 and PCM device #0:
-
-<p>
-
-<DL compact> <dt><b></b></dt>
- <dd>
-int card = 0, device = 0, err, fd, count, size, idx;
-
-<p>
-void *handle;
-
-<p>
-snd_pcm_format_t format;
-
-<p>
-char *buffer;
-</DL>
-<p>
-
-
-<p>
-
-<DL compact> <dt><b></b></dt>
- <dd>
-buffer = (char *)malloc(512 * 1024);
-
-<p>
-if (!buffer) return;
-
-<p>
-if ((err = snd_pcm_open(&handle, card, device,
-
-<p>
- SND_PCM_OPEN_PLAYBACK)) < 0) {
-
-<p>
- fprintf(stderr, "open failed: %s\n", snd_strerror( err ));
-
-<p>
- return;
-
-<p>
-}
-
-<p>
-bzero(&format sizeof(format));
-
-<p>
-format.format = SND_PCM_SFMT_MU_LAW;
-
-<p>
-format.rate = 8000;
-
-<p>
-format.channels = 1;
-
-<p>
-if ((err = snd_pcm_playback_format(handle, &format)) < 0) {
-
-<p>
- fprintf(stderr, "format setup failed: %s\n",
-
-<p>
- snd_strerror( err ));
-
-<p>
- snd_pcm_close( handle );
-
-<p>
- return;
-
-<p>
-}
-
-<p>
-fd = open("/tmp/test.au", O_RDONLY);
-
-<p>
-if (fd < 0) {
-
-<p>
- perror("open file");
-
-<p>
- snd_pcm_close(handle);
-
-<p>
- return;
-
-<p>
-}
-
-<p>
-idx = 0;
-
-<p>
-count = read(fd, buffer, 512 * 1024);
-
-<p>
-if (count <= 0) {
-
-<p>
- perror("read from file");
-
-<p>
- snd_pcm_close( handle );
-
-<p>
- return;
-
-<p>
-}
-
-<p>
-close( fd );
-
-<p>
-if (!memcmp(buffer, ".snd", 4)) {
-
-<p>
- idx = (buffer[4]<<24)|(buffer[5]<<16)|
-
-<p>
- (buffer[6]<<8)|(buffer[7]);
-
-<p>
- if (idx > 128) idx = 128;
-
-<p>
- if (idx > count) idx = count;
-
-<p>
-}
-
-<p>
-size = snd_pcm_write(handle, &buffer[ idx ], count - idx);
-
-<p>
-printf("Bytes written %i from %i...\n", size, count - idx);
-
-<p>
-snd_pcm_close(handle);
-
-<p>
-free(buffer);
-</DL>
-<p>
- <H3><A NAME="tth_sEc5.2">
-5.2</A> PCM Loopback Interface</H3>
-
-<p>
-This interface is designed to pass data currently being played or recorded from
-one application to another application for other processing like a graphical
-equalizer sample recorder etc... The programmer should be aware that each
-loopback connection eats CPU time (for data copying from the process which is
-doing the playback or record).
-
-<p>
-
-<H4>int snd_pcm_loopback_open(void **handle, int card, int device, int mode)</H4>
-
-<p>
-Creates a new handle and opens a connection to the kernel sound audio loopback
-interface for sound card number <i>card</i> (0-N) and audio device number
-<i>device</i>. Function also checks if protocol is compatible to prevent use
-of old programs with a new kernel API. Function returns zero if successful otherwise
-it returns an error code. Error code -EBUSY is returned when another process
-owns the selected direction.
-
-<p>
-The following modes should be used for the <i>mode</i> argument:
-
-<p>
-
-<DL compact> <dt><b></b></dt>
- <dd>
-#define SND_PCM_LB_OPEN_PLAYBACK 0
-
-<p>
-#define SND_PCM_LB_OPEN_RECORD 1
-</DL>
-<p>
-
-<H4>int snd_pcm_loopback_close(void *handle)</H4>
-
-<p>
-Frees all resources allocated with audio handle and closes the connection to
-the kernel sound audio interface. Function returns zero if successful, otherwise
-it returns an error code.
-
-<p>
-
-<H4>int snd_pcm_loopback_file_descriptor(void *handle)</H4>
-
-<p>
-Returns the file descriptor of the connection to the kernel sound audio interface.
-Function returns an error code if an error was encountered.
-
-<p>
-The file descriptor should be used for the <i>select(2)</i> synchronous multiplexer
-function for setting the read direction. Application should call <i>snd_pcm_loopback_read()</i>
-function if data is waiting to be read.
-
-<p>
-
-<H4>int snd_pcm_loopback_block_mode(void *handle, int enable) </H4>
-
-<p>
-Sets up block (default) or non-block mode for a handle. Block mode suspends
-execution of a program when <i>snd_pcm_loopback_read()</i> is called for
-the time until some data arrives for file descriptor. In non-block mode, programs
-aren't suspended and the above function returns immediately with the count of
-bytes which were read by the driver. When used in this way, don't try to use
-the entire buffer after the call, but instead process the number of bytes returned,
-and call the function again.
-
-<p>
-
-<H4>int snd_pcm_loopback_stream_mode(void *handle, int mode)</H4>
-
-<p>
-Sets up stream mode which should be one of these values:
-
-<p>
-
-<DL compact> <dt><b></b></dt>
- <dd>
-#define SND_PCM_LB_STREAM_MODE_RAW 0
-
-<p>
-#define SND_PCM_LB_STREAM_MODE_PACKET 1
-</DL>
-<p>
-Mode raw (default mode) means that the stream contains only PCM samples. Packet
-mode is more complicated. The stream contains a header at the begining of the
-packet. Information like data type and data size is contain in this header.
-
-<p>
-
-<DL compact> <dt><b></b></dt>
- <dd>
-#define SND_PCM_LB_TYPE_DATA 0 <i>/* sample data */</i>
-
-<p>
-#define SND_PCM_LB_TYPE_FORMAT 1 <i>/* PCM format */</i>
-</DL>
-<p>
-
-
-<p>
-
-<DL compact> <dt><b></b></dt>
- <dd>
-struct snd_pcm_loopback_header {
-
-<p>
- unsigned int size; <i>/* block size */</i>
-
-<p>
- unsigned int type; <i>/* block type (SND_PCM_LB_TYPE_*) */</i>
-
-<p>
-};
-</DL>
-<p>
-
-<H4>int snd_pcm_loopback_format(void *handle, snd_pcm_format_t *format) </H4>
-
-<p>
-Get current format for PCM stream.
-
-<p>
-
-<DL compact> <dt><b></b></dt>
- <dd>
-struct snd_pcm_format {
-
-<p>
- unsigned int format; <i>/* SND_PCM_SFMT_XXXX */</i>
-
-<p>
- unsigned int rate; <i>/* rate in Hz */</i>
-
-<p>
- unsigned int channels; <i>/* number of channels (voices) */</i>
-
-<p>
- unsigned char reserved[16];
-
-<p>
-};
-</DL>
-<p>
-
-<H4>ssize_t snd_pcm_loopback_read(void *handle, void *buffer, size_t size)</H4>
-
-<p>
-This function reads samples or loopback packets from the stream. Data depends
-on stream mode which should be set with <i>snd_pcm_loopback_stream_mode()</i>
-function. Function returns zero or positive value if record was success (value
-represents count of bytes which were successfully read from device) or negative
-error value if error occurred. Function will suspend process if block mode is
-active.
-
-<p>
- <H2><A NAME="tth_sEc6">
-6</A> RawMidi Interface</H2>
-
-<p>
-RawMidi Interface is designed to write or read raw (unchanged) MIDI data over
-the MIDI line. MIDI stands Musical Instrument Digital Interface and more informations
-about this standard can be found at <b>http://www.midi.org</b>.
-
-<p>
- <H3><A NAME="tth_sEc6.1">
-6.1</A> Low Level Layer</H3>
-
-<p>
-RawMidi devices are opened exclusively for a selected direction. While more
-than one process may not open a given MIDI device in the same direction simultaniously,
-seperate processes may open a single MIDI device in different directions (i.e.
-process one opens a MIDI device in playback direction and process two opens
-the same device in record direction). Audio devices (with MIDI ports) return
-EBUSY error to applications when other applications have already opened the
-requested direction.
-
-<p>
-
-<H4>int snd_rawmidi_open(void **handle, int card, int device, int mode)</H4>
-
-<p>
-Creates a new handle and opens a connection to the kernel sound audio interface
-for sound card number <i>card</i> (0-N) and rawmidi device number <i>device</i>.
-Function also checks if protocol is compatible to prevent use of old programs
-with a new kernel API. Function returns zero if successful, otherwise it returns
-an error code. Error code -EBUSY is returned when another process owns the selected
-direction.
-
-<p>
-The following modes should be used for the <i>mode</i> argument:
-
-<p>
-
-<DL compact> <dt><b></b></dt>
- <dd>
-#define SND_RAWMIDI_OPEN_OUTPUT (O_WRONLY)
-
-<p>
-#define SND_RAWMIDI_OPEN_INPUT (O_RDONLY)
-
-<p>
-#define SND_RAWMIDI_OPEN_DUPLEX (O_RDWR)
-</DL>
-<p>
-
-<H4>int snd_rawmidi_close(void *handle)</H4>
-
-<p>
-Frees all resources allocated with audio handle and closes the connection to
-the kernel sound rawmidi interface. Function returns zero if successful, otherwise
-it returns an error code.
-
-<p>
-
-<H4>int snd_rawmidi_file_descriptor(void *handle)</H4>
-
-<p>
-Returns the file descriptor of the connection to the kernel sound audio interface.
-Function returns an error code if an error was encountered.
-
-<p>
-The file descriptor should be used for the <i>select(2)</i> synchronous multiplexer
-function for setting the read direction. Application should call <i>snd_rawmidi_read()</i>
-or <i>snd_rawmidi_write()</i> functions if data is waiting to be read or
-a write can be performed. Calling these functions is highly recommended.
-
-<p>
-
-<H4>int snd_rawmidi_block_mode(void *handle, int enable) </H4>
-
-<p>
-Sets up block (default) or non-block mode for a handle. Block mode suspends
-execution of a program when <i>snd_rawmidi_read()</i> or <i>snd_rawmidi_write()</i>
-is called for the time which is needed for the actual output or input over of
-the selected limit. In non-block mode, programs aren't suspended and the above
-functions return immediately with the count of bytes which were read or written
-by the driver. When used in this way, don't try to use the entire buffer after
-the call, but instead process the number of bytes returned, and call the function
-again.
-
-<p>
-
-<H4>int snd_rawmidi_info(void *handle, snd_pcm_info_t *info)</H4>
-
-<p>
-Fills the <i>*info</i> structure with data about the PCM device selected
-by <i>*handle</i>. Function returns zero if successful, otherwise it returns
-an error code.
-
-<p>
-
-<DL compact> <dt><b></b></dt>
- <dd>
-<i>/*</i> device is capable rawmidi output *<i>/</i>
-
-<p>
-#define SND_RAWMIDI_INFO_OUTPUT 0x00000001
-
-<p>
-<i>/* device is capable rawmidi input */</i>
-
-<p>
-#define SND_RAWMIDI_INFO_INPUT 0x00000002
-
-<p>
-<i>/* device is capable duplex mode */</i>
-
-<p>
-#define SND_RAWMIDI_INFO_DUPLEX 0x00000004
-</DL>
-<p>
-
-
-<p>
-
-<DL compact> <dt><b></b></dt>
- <dd>
-struct snd_rawmidi_info {
-
-<p>
-<i> /* sound card type */</i>
-
-<p>
- unsigned int type;
-
-<p>
-<i> /* see SND_RAWMIDI_INFO_XXXX */</i>
-
-<p>
- unsigned int flags;
-
-<p>
-<i> /* ID of this PCM device */</i>
-
-<p>
- unsigned char id[32];
-
-<p>
-<i> /* name of this device */</i>
-
-<p>
- unsigned char name[80];
-
-<p>
-<i> /* reserved for future use */</i>
-
-<p>
- unsigned char reserved[64];
-
-<p>
-};
-</DL>
-<p>
-
-<H4>int snd_rawmidi_output_info(void *handle, snd_rawmidi_output_info_t
-*info)</H4>
-
-<p>
-Fills the *info structure with data about rawmidi output. Function returns
-zero if successful, otherwise it returns an error code.
-
-<p>
-
-<DL compact> <dt><b></b></dt>
- <dd>
-struct snd_rawmidi_output_info {
-
-<p>
-<i> /* count of output switches */</i>
-
-<p>
- unsigned int switches;
-
-<p>
-<i> /* reserved for future use */</i>
-
-<p>
- unsigned char reserved[64];
-
-<p>
-};
-</DL>
-<p>
-
-<H4>int snd_rawmidi_input_info(void *handle, snd_pcm_record_info_t *info)</H4>
-
-<p>
-Fills the *info structure. Returns zero if successful, otherwise it returns
-an error code.
-
-<p>
-
-<DL compact> <dt><b></b></dt>
- <dd>
-struct snd_rawmidi_input_info {
-
-<p>
-<i> /* count of output switches */</i>
-
-<p>
- unsigned int switches;
-
-<p>
-<i> /* reserved for future use */</i>
-
-<p>
- unsigned char reserved[64];
-
-<p>
-};
-</DL>
-<p>
-
-<H4>int snd_rawmidi_output_switches(void *handle)</H4>
-
-<p>
-Returns count of rawmidi output switches. In this context 'switch' means universal
-control interface between kernel and application which allows various types
-of control. Function returns count if successful, otherwise it returns an error
-code. Return value should be zero if sound card doesn't have any rawmidi output
-switch.
-
-<p>
-
-<H4>int snd_rawmidi_output_switch(void *handle, const char *switch_id)</H4>
-
-<p>
-Returns index for switch with name <i>switch_id</i>. Function returns switch
-index if successful, otherwise it returns an error code.
-
-<p>
-
-<H4>int snd_rawmidi_output_switch_read(void *handle int switchnsnd_rawmidi_switch_t *data)</H4>
-
-<p>
-Fills the <i>*data</i> structure with data about switch with index <i>switchn</i>.
-Function returns zero if successful, otherwise it returns an error code.
-
-<p>
-
-<DL compact> <dt><b></b></dt>
- <dd>
-<i>/* 0 or 1 (enable member of union) */</i>
-
-<p>
-#define SND_PCM_SW_TYPE_BOOLEAN 0
-
-<p>
-<i>/* 0 to 255 - from low to high (data8[0] member of union) */</i>
-
-<p>
-#define SND_PCM_SW_TYPE_BYTE 1
-
-<p>
-<i>/* 0 to 65535 - from low to high (data16[0] member of union) */</i>
-
-<p>
-#define SND_PCM_SW_TYPE_WORD 2
-
-<p>
-<i>/* 0 to 4294967296 ¯ from low to high (data32[0] member of union) */</i>
-
-<p>
-#define SND_PCM_SW_TYPE_DWORD 3
-
-<p>
-<i>/* user type - no type control */</i>
-
-<p>
-#define SND_PCM_SW_TYPE_USER (~0)
-</DL>
-<p>
-
-
-<p>
-
-<DL compact> <dt><b></b></dt>
- <dd>
-struct snd_rawmidi_switch {
-
-<p>
- <i>/* switch index (filled by application) */</i>
-
-<p>
- unsigned int switchn;
-
-<p>
- <i>/* identification of switch (for driver) */</i>
-
-<p>
- unsigned char name[32];
-
-<p>
- <i>/* type of switch value ¯ See SND_PCM_SW_TYPE_XXXX */</i>
-
-<p>
- unsigned int type;
-
-<p>
- <i>/* low range value */</i>
-
-<p>
- unsigned int low;
-
-<p>
- <i>/* high range value */</i>
-
-<p>
- unsigned int high;
-
-<p>
- union {
-
-<p>
- unsigned int enable; <i>/* 0 = off 1 = on */</i>
-
-<p>
- unsigned char data8[32]; <i>/* 8-bit data */</i>
-
-<p>
- unsigned short data16[16]; <i>/* 16-bit data */</i>
-
-<p>
- unsigned int data32[8]; <i>/* 32-bit data */</i>
-
-<p>
- } value;
-
-<p>
- <i>/* reserved for future use ¯ must be zero !!! */</i>
-
-<p>
- unsigned char reserved[32];
-
-<p>
-}
-</DL>
-<p>
-
-<H4>int snd_rawmidi_output_switch_write(void *handle int switchnsnd_rawmidi_switch_t *data)</H4>
-
-<p>
-Writes the <i>*data</i> structure with data about switch with index <i>switchn</i>
-to kernel. Function returns zero if successful, otherwise it returns an error
-code.
-
-<p>
-
-<H4>int snd_rawmidi_input_switches(void *handle)</H4>
-
-<p>
-Returns count of rawmidi input switches. In this context 'switch' means universal
-control interface between kernel and application which allows various types
-of control. Function returns count if successful, otherwise it returns an error
-code. Return value should be zero if sound card doesn't have any rawmidi input
-switch.
-
-<p>
-
-<H4>int snd_rawmidi_input_switch(void *handle, const char *switch_id)</H4>
-
-<p>
-Returns index for switch with name <i>switch_id</i>. Function returns switch
-index if successful, otherwise it returns an error code.
-
-<p>
-
-<H4>int snd_rawmidi_input_switch_read(void *handle int switchnsnd_rawmidi_switch_t *data)</H4>
-
-<p>
-Fills the <i>*data</i> structure with data about switch with index <i>switchn</i>.
-Function returns zero if successful, otherwise it returns an error code.
-
-<p>
-
-<H4>int snd_rawmidi_input_switch_write(void *handle int switchnsnd_rawmidi_switch_t *data)</H4>
-
-<p>
-Writes the <i>*data</i> structure with data about switch with index <i>switchn</i>
-to kernel. Function returns zero if successful, otherwise it returns an error
-code.
-
-<p>
-
-<H4>int snd_rawmidi_output_params(void *handle, snd_rawmidi_output_params_t
-*params)</H4>
-
-<p>
-Sets various parameters for output direction. Function returns zero if successful,
-otherwise it returns an error code.
-
-<p>
-
-<DL compact> <dt><b></b></dt>
- <dd>
-struct snd_rawmidi_output_params {
-
-<p>
- int size;
-
-<p>
- int max;
-
-<p>
- int room;
-
-<p>
-<i> /* reserved for future use - must be filled with zero */</i>
-
-<p>
- unsigned char reserved[16];
-
-<p>
-};
-</DL>
-<p>
-
-<DL compact><dt><b></b></dt>
- <dd> [size]Requested queue size of output buffer in bytes (default setup is 4096
-[i386] or 8192 [alpha] bytes - this is system architecture dependent).
-<dt><b></b></dt>
- <dd> [max]Maximum number of bytes in queue for wakeup. If the current byte count
-of filled portion of output buffer is greater than this value the driver will
-block an application or return immediately if non block mode is active.
-<dt><b></b></dt>
- <dd> [room]Minimum number of bytes writable for wakeup. This value should be in most
-cases 1 which means return back to application if at least one byte is free
-in output buffer.
-</DL>
-<p>
-
-<H4>int snd_rawmidi_input_params(void *handle, snd_rawmidi_input_params_t
-*params)</H4>
-
-<p>
-Function sets various parameters for the recording direction. Function returns
-zero if successful, otherwise it returns an error code.
-
-<p>
-
-<DL compact> <dt><b></b></dt>
- <dd>
-struct snd_rawmidi_input_params {
-
-<p>
- int size;
-
-<p>
- int min;
-
-<p>
-<i> /* reserved for future use - must be filled with zero */</i>
-
-<p>
- unsigned char reserved[16];
-
-<p>
-};
-</DL>
-<p>
-
-<DL compact><dt><b></b></dt>
- <dd> [size]Requested queue size of input buffer in bytes (default setup is 4096 [i386]
-or 8192 [alpha] bytes - this is system architecture dependent).
-<dt><b></b></dt>
- <dd> [min]Minimum filled bytes in queue for wakeup. Driver blocks the application
-(if block mode is selected) until input buffer is filled with fewer than the
-number of bytes specified with this value.
-</DL>
-<p>
-
-<H4>int snd_rawmidi_output_status(void *handle, snd_rawmidi_output_status_t
-*status)</H4>
-
-<p>
-Fills the <i>*status</i> structure. Function returns zero if successful,
-otherwise it returns an error code.
-
-<p>
-
-<DL compact> <dt><b></b></dt>
- <dd>
-struct snd_rawmidi_output_status {
-
-<p>
- int size;
-
-<p>
- int count;
-
-<p>
- int queue;
-
-<p>
-<i> /* reserved for future use - must be filled with zero */</i>
-
-<p>
- unsigned char reserved[16];
-
-<p>
-};
-</DL>
-<p>
-
-<DL compact><dt><b></b></dt>
- <dd> [size]Size of currently allocated queue in bytes.
-<dt><b></b></dt>
- <dd> [count]Count of bytes writable without blocking.
-<dt><b></b></dt>
- <dd> [queue]Count of bytes in queue (number of bytes waiting to be output).
-</DL>
-<p>
-
-<H4>int snd_rawmidi_input_status(void *handle, snd_rawmidi_input_status_t
-*status)</H4>
-
-<p>
-Fills the <i>*status</i> structure. Function returns zero if successful,
-otherwise it returns an error code.
-
-<p>
-
-<DL compact> <dt><b></b></dt>
- <dd>
-struct snd_rawmidi_input_status {
-
-<p>
- int size;
-
-<p>
- int count;
-
-<p>
- int free;
-
-<p>
- int overrun;
-
-<p>
-<i> /* reserved for future use - must be filled with zero */</i>
-
-<p>
- unsigned char reserved[16];
-
-<p>
-};
-</DL>
-<p>
-
-<DL compact><dt><b></b></dt>
- <dd> [size]Size of currently allocated queue in bytes.
-<dt><b></b></dt>
- <dd> [count]Count of bytes readable without blocking.
-<dt><b></b></dt>
- <dd> [free]Count of bytes in queue still free.
-<dt><b></b></dt>
- <dd> [overrun]This value tells the application the count of overruns since the last
-call to <i>snd_rawmidi_input_status</i>.
-</DL>
-<p>
-
-<H4>int snd_rawmidi_drain_output(void *handle)</H4>
-
-<p>
-This function stops and drains (destroys) the output queue immediately. Function
-returns zero if successful, otherwise it returns an error code.
-
-<p>
-
-<H4>int snd_rawmidi_flush_output(void *handle)</H4>
-
-<p>
-This function flushes the output queue. It blocks the program while the all
-the waiting bytes in kernel output queue are processed. Function returns zero
-if successful, otherwise it returns an error code.
-
-<p>
-
-<H4>int snd_rawmidi_flush_input(void *handle)</H4>
-
-<p>
-This function flushes (destroys) input queue. Function returns zero if successful,
-otherwise it returns an error code.
-
-<p>
-
-<H4>ssize_t snd_rawmidi_write(void *handle, const void *buffer, size_t
-size)</H4>
-
-<p>
-Writes bytes to the output queue. Function returns zero or positive value if
-the write was successful (value represents count of bytes which were successfully
-written to the device) or an error value if error occurred. Function will suspend
-the process if block mode is active.
-
-<p>
-
-<H4>ssize_t snd_rawmidi_read(void *handle, void *buffer, size_t size)</H4>
-
-<p>
-Function reads bytes from input queue. Function returns zero or positive value
-if the read was successful (value represents count of bytes which were successfully
-read from device) or negative error value if error occurred. Function will suspend
-the process if block mode is active.
-
-<p>
- <H4><A NAME="tth_sEc6.1.1">
-6.1.1</A> Example</H4>
-
-<p>
-The following example shows how to send a control sequence (such as SysEx) to
-a MIDI device. Sound card #0 and rawmidi device #0 are used here:
-
-<p>
-
-<DL compact> <dt><b></b></dt>
- <dd>
-int card = 0, device = 0, err, fd, count, size;
-
-<p>
-void *handle;
-
-<p>
-snd_pcm_format_t format;
-
-<p>
-char *buffer;
-</DL>
-<p>
-
-
-<p>
-
-<DL compact> <dt><b></b></dt>
- <dd>
-buffer = (char *)malloc(64 * 1024);
-
-<p>
-if (!buffer) return;
-
-<p>
-if ((err = snd_rawmidi_open(&handle, card, device,
-
-<p>
- SND_RAWMIDI_OPEN_OUTPUT)) < 0) {
-
-<p>
- fprintf(stderr, "open failed: %s\n", snd_strerror( err ));
-
-<p>
- return;
-
-<p>
-}
-
-<p>
-if ((err = snd_rawmidi_block_mode(handle 1)) < 0) {
-
-<p>
- fprintf(stderr, "block failed: %s\n", snd_strerror( err ));
-
-<p>
- snd_rawmidi_close(handle);
-
-<p>
- return;
-
-<p>
-}
-
-<p>
-fd = open("/tmp/test.sysex", O_RDONLY);
-
-<p>
-if (fd < 0) {
-
-<p>
- perror("open file");
-
-<p>
- snd_rawmidi_close(handle);
-
-<p>
- return;
-
-<p>
-}
-
-<p>
-idx = 0;
-
-<p>
-count = read(fd, buffer, 64 * 1024);
-
-<p>
-if (count <= 0) {
-
-<p>
- perror("read from file");
-
-<p>
- snd_rawmidi_close(handle);
-
-<p>
- return;
-
-<p>
-}
-
-<p>
-close(fd);
-
-<p>
-size = snd_rawmidi_write(handle, &buffer, count);
-
-<p>
-printf("Bytes written %i from %i...\n", size, count);
-
-<p>
-snd_rawmidi_close(handle);
-
-<p>
-free(buffer);
-
-<p>
-</DL>
-<p><hr><small>File translated from T<sub><font size="-1">E</font></sub>X by <a href="http://hutchinson.belmont.ma.us/tth/">T<sub><font size="-1">T</font></sub>H</a>, version 1.98.<br>On 19 Jan 1999, 16:22.</small>
-</HTML>
+++ /dev/null
-#This file was created by <emng> Mon Jan 11 02:36:51 1999
-#LyX 1.0 (C) 1995-1998 Matthias Ettrich and the LyX Team
-\lyxformat 2.15
-\textclass article
-\language default
-\inputencoding default
-\fontscheme default
-\graphics default
-\paperfontsize default
-\spacing single
-\papersize Default
-\paperpackage widemarginsa4
-\use_geometry 0
-\use_amsmath 0
-\paperorientation portrait
-\secnumdepth 3
-\tocdepth 3
-\paragraph_separation indent
-\defskip medskip
-\quotes_language english
-\quotes_times 2
-\papercolumns 1
-\papersides 1
-\paperpagestyle default
-
-\layout Title
-\added_space_top vfill \added_space_bottom vfill
-Advanced Linux Sound Architecture - Library API
-\layout Author
-
-
-\series bold
-Jaroslav Kysela <perex@suse.cz>
-\series default
- with assistance from Alan Robinson and Fred Floberg
-\layout Date
-
-1998-11-11
-\layout Standard
-\align center
-
-\shape italic
-This document describes, in full detail, the Advanced Linux Sound Architecture
- library API.
-
-\layout Standard
-
-
-\begin_inset LatexCommand \tableofcontents
-
-\end_inset
-
-
-\layout Section
-
-Introduction
-\layout Standard
-
-The Advanced Linux Sound Architecture comes with a kernel API & library
- API.
- This document describes the library API and how it interfaces with the
- kernel API.
- The kernal API will probably never be documented in standalone form.
-
-\layout Standard
-
-Application programmers should use the library API rather than kernel API.
- The Library offers 100% of the functionally of the kernel API, but add
- major improvements in usability, making the application code simpler and
- better looking.
- In addition, some of the some fixes/compatibility code may be placed in
- the library code instead of the kernel driver.
-
-\layout Standard
-
-For a complete list of all variables and functions in the API you should
- look at the following header files:
-\layout Itemize
-
-/usr/include/sys/asoundlib.h
-\layout Itemize
-
-/usr/include/linux/asound.h
-\layout Itemize
-
-/usr/include/linux/asoundid.h
-\layout Section
-
-Error Codes
-\layout Standard
-
-All functions return int (or some sort of signed value).
- If this value is negative it represents an error code.
- Codes up to
-\shape italic
-SND_ERROR_BEGIN (500000)
-\shape default
- represent standard system errors.
- Codes equal to or greather than this value represent sound library API
- errors.
- All error codes begin with the prefix
-\shape italic
-SND_ERROR_
-\shape default
-.
-
-\layout Subsection
-
-Error Codes in Detail
-\layout Standard
-\added_space_top 0.3cm \added_space_bottom 0.3cm \LyXTable
-multicol5
-1 2 0 0 -1 -1 -1 -1
-1 1 0 0
-8 1 1 "" ""
-8 1 1 "" ""
-0 8 1 0 0 0 0 "" ""
-0 8 1 0 0 0 0 "" ""
-
-SND_ERROR_UNCOMPATIBLE_VERSION
-\newline
-500000
-\layout Standard
-
-This error is caused if the driver uses an incompatible kernel API for this
- interface and hence the library doesn't know how this API can be used.
-
-\layout Subsection
-
-Functions
-\layout Subsubsection*
-
-const char *snd_strerror(int errnum)
-\layout Standard
-
-This function converts an error code to a string.
- Its functionality is the same as the
-\shape italic
-strerror
-\shape default
- function from the standard C library, but this function returns error message
- strings for sound error codes, as well.
-\layout Section
-
-Control Interface
-\layout Standard
-
-The control interface gives applications various information about the currently
- installed sound driver in the system.
- The interface should be used to detect if another sound interface is present
- for a selected soundcard or, for example, to create a list of devices (MIXER,
- PCM etc) from which the user can select.
-\layout Subsection
-
-Low-Level Layer
-\layout Subsubsection*
-
-int snd_cards(void)
-\layout Standard
-
-Returns the number of soundcards present in the system, if any.
- Otherwise it returns a negative value, which maps to an error code.
- This function will return 0 if no soundcards are detected.
-\layout Subsubsection*
-
-unsigned int snd_cards_mask(void)
-\layout Standard
-
-Returns the bitmap of soundcards present in the system, if any.
- This function will return 0 if no soundcards are detected.
- The first soundcard is represented with bit 0 (0x00000001).
- See the documentation on installing ALSA and /etc/conf.modules configuration
- for information on assigning numbers to soundcards.
-\layout Subsubsection*
-
-int snd_card_name(const char *name)
-\layout Standard
-
-Returns soundcard number for appropriate soundcard name.
- String
-\shape italic
-name
-\shape default
- can contain word identification for card (ALSA driver allows the user choose
- card identification using snd_id module parameter) or soundcard index (1-N)
- encoded into ASCII.
-\layout Subsubsection*
-
-int snd_ctl_open(void **handle, int card)
-\layout Standard
-
-Creates a new handle and opens communication with the kernel sound control
- interface for soundcard number
-\shape italic
-card
-\shape default
- (0-N).
- The function also checks if the protocol is compatible, so as to prevent
- the use of old programs with a new kernel API.
- Function returns zero if successful, otherwise an error code is returned.
-
-\layout Subsubsection*
-
-int snd_ctl_close(void *handle)
-\layout Standard
-
-Frees all resources allocated with control handle and closes the kernel
- sound control interface.
- This function returns zero if successful, otherwise it returns an error
- code.
-\layout Subsubsection*
-
-int snd_ctl_file_descriptor(void *handle)
-\layout Standard
-
-Returns a file descriptor for the kernel sound control interface.
- This function is normally only used in very special cases.
- This function returns a negative error code if an error was encountered.
-\layout Subsubsection*
-
-int snd_ctl_hw_info(void *handle, snd_ctl_hw_info_t *info)
-\layout Standard
-
-Fills the info structure with data about the sound hardware referenced by
- handle.
- This function returns zero if successful, otherwise it returns an error
- code.
-\layout LyX-Code
-
-
-\shape italic
-/* driver has MIDI interface */
-\layout LyX-Code
-
-#define SND_CTL_GCAPS_MIDI
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-0x0000001
-\layout LyX-Code
-
-
-\shape italic
-/* soundcard has synthesizer */
-\layout LyX-Code
-
-#define SND_CTL_LCAPS_SYNTH
-\protected_separator
-
-\protected_separator
- 0x0000001
-\layout LyX-Code
-
-
-\shape italic
-/* soundcard has RAW FM/OPL3 */
-\layout LyX-Code
-
-#define SND_CTL_LCAPS_RAWFM
-\protected_separator
-
-\protected_separator
- 0x0000002
-\layout Standard
-
-
-\protected_separator
-
-\layout LyX-Code
-
-struct snd_ctl_hw_info {
-\layout LyX-Code
-
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\shape italic
-/* type of card - see SND_CARD_TYPE_XXXX */
-\layout LyX-Code
-
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
- unsigned int type;
-\layout LyX-Code
-
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\shape italic
-/* global capabilities - see SND_CTL_GCAPS_XXXX*/
-\layout LyX-Code
-
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
- unsigned int gcaps;
-\layout LyX-Code
-
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\shape italic
-/* local capabilities \i \={ }
- see SND_CTL_LCAPS_XXXX */
-\layout LyX-Code
-
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
- unsigned int lcaps;
-\layout LyX-Code
-
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\shape italic
-/* count of PCM devices (0 to N) */
-\layout LyX-Code
-
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-unsigned int pcmdevs;
-\layout LyX-Code
-
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\shape italic
-/* count of MIXER devices (0 to N)*/
-\layout LyX-Code
-
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
- unsigned int mixerdevs;
-\layout LyX-Code
-
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\shape italic
-/* count of raw MIDI devices (0 to N) */
-\layout LyX-Code
-
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-unsigned int mididevs;
-\layout LyX-Code
-
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\shape italic
-/* ID of card (user selectable) */
-\layout LyX-Code
-
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-char id[80];
-\layout LyX-Code
-
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\shape italic
-/* name/info text about soundcard */
-\layout LyX-Code
-
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
- char name[80];
-\layout LyX-Code
-
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\shape italic
-/* count of control switches */
-\layout LyX-Code
-
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
- unsigned int switches;
-\layout LyX-Code
-
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\shape italic
-/* reserved for future use */
-\layout LyX-Code
-
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
- unsigned char reserved[124];
-\layout LyX-Code
-
-};
-\layout Subsubsection*
-
-int snd_ctl_switches(void *handle)
-\layout Standard
-
-Returns the number of control switches.
- In this context 'switch' means universal control interface between kernel
- and application which allows various types of control.
- Function returns count if successful, otherwise it returns an error code.
- Return value should be zero if the soundcard doesn't have any control switches.
-\layout Subsubsection*
-
-int snd_ctl_switch(void *handle, const char *switch_id)
-\layout Standard
-
-Returns the index for the switch with the name
-\shape italic
-switch_id
-\shape default
-.
- This function returns switch index if successful, otherwise it returns
- an error code.
-\layout Subsubsection*
-
-int snd_ctl_switch_read(void *handle\i \c{ }
- int switchn\i \c{ }
- snd_ctl_switch_t *data)
-\layout Standard
-
-Fills the
-\shape italic
-*data
-\shape default
- structure with data about the switch with index
-\shape italic
-switchn
-\shape default
-.
- This function returns zero if successful, otherwise it returns an error
- code.
-\layout LyX-Code
-
-
-\shape italic
-/* 0 or 1 (enable member of union) */
-\layout LyX-Code
-
-#define SND_CTL_SW_TYPE_BOOLEAN
-\protected_separator
-
-\protected_separator
-
-\protected_separator
- 0
-\layout LyX-Code
-
-
-\shape italic
-/* 0 to 255 - from low to high (data8[0] member of union) */
-\layout LyX-Code
-
-#define SND_CTL_SW_TYPE_BYTE
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-1
-\layout LyX-Code
-
-
-\shape italic
-/* 0 to 65535 - from low to high (data16[0] member of union) */
-\layout LyX-Code
-
-#define SND_CTL_SW_TYPE_WORD
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-2
-\layout LyX-Code
-
-
-\shape italic
-/* 0 to 4294967296 \i \={ }
- from low to high (data32[0] member of union) */
-\layout LyX-Code
-
-#define SND_CTL_SW_TYPE_DWORD
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
- 3
-\layout LyX-Code
-
-
-\shape italic
-/* user type - no type control */
-\layout LyX-Code
-
-#define SND_CTL_SW_TYPE_USER
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-(~0)
-\layout Standard
-
-
-\protected_separator
-
-\layout LyX-Code
-
-
-\shape italic
-/* well known (named) switches */
-\layout LyX-Code
-
-#define SND_CTL_SW_JOYSTICK
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
- "Joystick"
-\layout LyX-Code
-
-#define SND_CTL_SW_JOYSTICK_ADDRESS
-\protected_separator
- "Joystick Address"
-\layout LyX-Code
-
-#define SND_CTL_SW_JOYSTICK_SPEED
-\protected_separator
-
-\protected_separator
- "Joystick Speed"
-\layout Standard
-
-
-\protected_separator
-
-\layout LyX-Code
-
-struct snd_ctl_switch {
-\layout LyX-Code
-
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\shape italic
-/* switch index (filled by application) */
-\layout LyX-Code
-
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
- unsigned int switchn;
-\layout LyX-Code
-
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\shape italic
-/* indentification of switch (for driver) */
-\layout LyX-Code
-
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
- unsigned char name[32];
-\layout LyX-Code
-
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\shape italic
-/* type of switch value - See SND_CTL_SW_TYPE_XXXX */
-\layout LyX-Code
-
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
- unsigned int type;
-\layout LyX-Code
-
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\shape italic
-/* low range value */
-\layout LyX-Code
-
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
- unsigned int low;
-\layout LyX-Code
-
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\shape italic
-/* high range value */
-\layout LyX-Code
-
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
- unsigned int high;
-\layout LyX-Code
-
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
- union {
-\layout LyX-Code
-
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
- unsigned int enable;
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\shape italic
-/* 0 = off\i \c{ }
- 1 = on */
-\layout LyX-Code
-
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
- unsigned char data8[32];
-\protected_separator
-
-\protected_separator
-
-\shape italic
-/* 8-bit data */
-\layout LyX-Code
-
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
- unsigned short data16[16];
-\protected_separator
-
-\shape italic
-/* 16-bit data */
-\layout LyX-Code
-
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
- unsigned int data32[8];
-\protected_separator
-
-\protected_separator
-
-\shape italic
-/* 32-bit data */
-\layout LyX-Code
-
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
- } value;
-\layout LyX-Code
-
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\shape italic
-/* reserved for future use \i \={ }
- must be zero !!! */
-\layout LyX-Code
-
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
- unsigned char reserved[32];
-\layout LyX-Code
-
-}
-\layout Subsubsection*
-
-int snd_ctl_switch_write(void *handle\i \c{ }
- int switchn\i \c{ }
- snd_ctl_switch_t *data)
-\layout Standard
-
-Writes the
-\shape italic
-*data
-\shape default
- structure with data about the switch with index
-\shape italic
-switchn
-\shape default
- to kernel.
- This function returns zero if successful, otherwise it returns an error
- code.
-\layout Subsubsection*
-
-int snd_ctl_mixer_info(void *handle, int dev, snd_mixer_info_t *info)
-\layout Standard
-
-Fills the *info structure with data about the mixer device.
- Returns zero if successful, otherwise it returns an error code.
- Details about the
-\shape italic
-snd_mixer_info_t
-\shape default
- structure are in the
-\series bold
-Mixer Interface
-\series default
- section.
- The argument
-\shape italic
-dev
-\shape default
- specifies the device number for the appropriate soundcard.
- Its range is 0 to N where N is determined by
-\shape italic
-struct snd_ctl_hw_info->mixerdevs - 1
-\shape default
-.
- It should be used to collect information about mixer devices.
-\layout Subsubsection*
-
-int snd_ctl_mixer_switches(void *handle)
-\layout Standard
-
-Returns count of mixer switches.
- In this context 'switch' means universal control interface between kernel
- and application which allows various types control.
- This function returns count if successful, otherwise it returns an error
- code.
- Return value should be zero if soundcard doesn't have any mixer switches.
-\layout Subsubsection*
-
-int snd_ctl_mixer_switch(void *handle, const char *switch_id)
-\layout Standard
-
-Returns the index for the switch with the name
-\shape italic
-switch_id
-\shape default
-.
- This function returns switch index if successful, otherwise it returns
- an error code.
-\layout Subsubsection*
-
-int snd_ctl_mixer_switch_read(void *handle\i \c{ }
- int switchn\i \c{ }
- snd_mixer_switch_t
- *data)
-\layout Standard
-
-Fills the
-\shape italic
-*data
-\shape default
- structure with data about the switch with index
-\shape italic
-switchn
-\shape default
-.
- This function returns zero if successful, otherwise it returns an error
- code.
- Details about the
-\shape italic
-snd_mixer_switch_t
-\shape default
- structure are in the
-\series bold
-Mixer Interface
-\series default
- section.
-\layout Subsubsection*
-
-int snd_ctl_mixer_switch_write(void *handle\i \c{ }
- int switchn\i \c{ }
- snd_mixer_switch_t
- *data)
-\layout Standard
-
-Writes the
-\shape italic
-*data
-\shape default
- structure with data about switch with index
-\shape italic
-switchn
-\shape default
- to kernel.
- Function returns zero if successful, otherwise it returns an error code.
- Details about the
-\shape italic
-snd_mixer_switch_t
-\shape default
- structure are in the
-\series bold
-Mixer Interface
-\series default
- Interface section.
-\layout Subsubsection*
-
-int snd_ctl_pcm_info(void *handle, int dev, snd_pcm_info_t *info)
-\layout Standard
-
-Fills the
-\shape italic
-*info
-\shape default
- structure with data about the PCM device.
- Function returns zero if successful, otherwise it returns an error code.
- Details about the
-\shape italic
-snd_pcm_info_t
-\shape default
- structure are in the
-\series bold
-Digital Audio (PCM)
-\series default
- Interface section.
- The argument
-\shape italic
-dev
-\shape default
- selects the device number for the sound card referenced by
-\shape italic
-*handle
-\shape default
-.
- Its range is 0 to N where N is
-\shape italic
-struct snd_ctl_hw_info->pcmdevs - 1
-\shape default
-.
- This function will work if the selected PCM device is busy, too.
- It should be used to collect information about PCM devices without exclusive
- lock.
-
-\layout Subsubsection*
-
-int snd_ctl_pcm_playback_info(void *handle, int dev, snd_pcm_playback_info_t
- *info)
-\layout Standard
-
-Fills the
-\shape italic
-*info
-\shape default
- structure with data about the PCM device and playback direction.
- Function returns zero if successful, otherwise it returns an error code.
- Details about the
-\shape italic
-snd_pcm_playback_info_t
-\shape default
- structure are in the
-\series bold
-Digital Audio (PCM) Interface
-\series default
- section.
- The argument
-\shape italic
-dev
-\shape default
- selects the device number for the sound card referenced by
-\shape italic
-*handle
-\shape default
-.
- Its range is 0 to N where N is
-\shape italic
-struct snd_ctl_hw_info->pcmdevs - 1
-\shape default
-.
- This function will work if the selected PCM device is busy, too.
- It should be used to collect information about PCM devices without exclusive
- lock.
-
-\layout Subsubsection*
-
-int snd_ctl_pcm_playback_switches(void *handle)
-\layout Standard
-
-Returns count of PCM playback switches.
- In this context 'switch' means universal control interface between kernel
- and application which allows various types of control.
- Function returns count if successful, otherwise it returns an error code.
- Return value should be zero if sound card doesn't have any PCM playback
- switch.
-\layout Subsubsection*
-
-int snd_ctl_pcm_playback_switch(void *handle, const char *switch_id)
-\layout Standard
-
-Returns index for switch with name
-\shape italic
-switch_id
-\shape default
-.
- Function returns switch index if successful, otherwise it returns an error
- code.
-\layout Subsubsection*
-
-int snd_ctl_pcm_playback_switch_read(void *handle\i \c{ }
- int switchn\i \c{ }
- snd_pcm_switch_t
- *data)
-\layout Standard
-
-Fills the
-\shape italic
-*data
-\shape default
- structure with data about switch with index
-\shape italic
-switchn
-\shape default
-.
- Function returns zero if successful, otherwise it returns an error code.
- Details about the
-\shape italic
-snd_pcm_switch_t
-\shape default
- structure are in the
-\series bold
-Digital Audio (PCM)
-\series default
- Interface section.
-\layout Subsubsection*
-
-int snd_ctl_pcm_playback_switch_write(void *handle\i \c{ }
- int switchn\i \c{ }
- snd_pcm_switch_t
- *data)
-\layout Standard
-
-Writes the
-\shape italic
-*data
-\shape default
- structure with data about switch with index
-\shape italic
-switchn
-\shape default
- to kernel.
- Function returns zero if successful, otherwise it returns an error code.
- Details about the
-\shape italic
-snd_pcm_switch_t
-\shape default
- structure are in the
-\series bold
-Digital Audio (PCM)
-\series default
- Interface section.
-\layout Subsubsection*
-
-int snd_ctl_pcm_record_info(void *handle, int dev, snd_pcm_record_info_t
- *info)
-\layout Standard
-
-Fills the
-\shape italic
-*info
-\shape default
- structure with data about the PCM device and record direction.
- Function returns zero if successful, otherwise it returns an error code.
- Details about the
-\shape italic
-snd_pcm_record_info_t
-\shape default
- structure are in the
-\series bold
-Digital Audio (PCM) Interface
-\series default
- section.
- The argument
-\shape italic
-dev
-\shape default
- selects the device number for the sound card referenced by
-\shape italic
-*handle
-\shape default
-.
- Its range is 0 to N where N is
-\shape italic
-struct snd_ctl_hw_info->pcmdevs - 1
-\shape default
-.
- This function will work if the selected PCM device is busy, too.
- It should be used to collect information about PCM devices without exclusive
- lock.
-
-\layout Subsubsection*
-
-int snd_ctl_pcm_record_switches(void *handle)
-\layout Standard
-
-Returns count of PCM record switches.
- In this context 'switch' means universal control interface between kernel
- and application which allows various types of control.
- Function returns count if successful, otherwise it returns an error code.
- Return value should be zero if sound card doesn't have any PCM record switch.
-\layout Subsubsection*
-
-int snd_ctl_pcm_record_switch(void *handle, const char *switch_id)
-\layout Standard
-
-Returns index for switch with name
-\shape italic
-switch_id
-\shape default
-.
- Function returns switch index if successful, otherwise it returns an error
- code.
-\layout Subsubsection*
-
-int snd_ctl_pcm_record_switch_read(void *handle\i \c{ }
- int switchn\i \c{ }
- snd_pcm_switch_t
- *data)
-\layout Standard
-
-Fills the
-\shape italic
-*data
-\shape default
- structure with data about switch with index
-\shape italic
-switchn
-\shape default
-.
- Function returns zero if successful, otherwise it returns an error code.
- Details about the
-\shape italic
-snd_pcm_switch_t
-\shape default
- structure are in the
-\series bold
-Digital Audio (PCM)
-\series default
- Interface section.
-\layout Subsubsection*
-
-int snd_ctl_pcm_record_switch_write(void *handle\i \c{ }
- int switchn\i \c{ }
- snd_pcm_switch_t
- *data)
-\layout Standard
-
-Writes the
-\shape italic
-*data
-\shape default
- structure with data about switch with index
-\shape italic
-switchn
-\shape default
- to kernel.
- Function returns zero if successful, otherwise it returns an error code.
- Details about the
-\shape italic
-snd_pcm_switch_t
-\shape default
- structure are in the
-\series bold
-Digital Audio (PCM)
-\series default
- Interface section.
-\layout Subsubsection*
-
-int snd_ctl_rawmidi_info(void *handle, int dev, snd_rawmidi_info_t *info)
-\layout Standard
-
-Fills the
-\shape italic
-*info
-\shape default
- structure with data about the rawmidi device.
- Function returns zero if successful, otherwise it returns an error code.
- Details about the
-\shape italic
-snd_rawmidi_info_t
-\shape default
- structure are in the
-\series bold
-RawMidi Interface
-\series default
- section.
- The argument
-\shape italic
-dev
-\shape default
- selects the device number for the sound card referenced by
-\shape italic
-*handle
-\shape default
-.
- Its range is 0 to N where N is
-\shape italic
-struct snd_ctl_hw_info->mididevs - 1
-\shape default
-.
- This function will work if the selected rawmidi device is busy, too.
- It should be used to collect information about rawmidi devices without
- exclusive lock.
-
-\layout Subsubsection*
-
-int snd_ctl_rawmidi_output_info(void *handle, int dev, snd_rawmidi_output_info_t
- *info)
-\layout Standard
-
-Fills the
-\shape italic
-*info
-\shape default
- structure with data about the rawmidi device and output direction.
- Function returns zero if successful, otherwise it returns an error code.
- Details about the
-\shape italic
-snd_pcm_playback_info_t
-\shape default
- structure are in the
-\series bold
-RawMidi Interface
-\series default
- section.
- The argument
-\shape italic
-dev
-\shape default
- selects the device number for the sound card referenced by
-\shape italic
-*handle
-\shape default
-.
- Its range is 0 to N where N is
-\shape italic
-struct snd_ctl_hw_info->mididevs - 1
-\shape default
-.
- This function will work if the selected rawmidi device is busy, too.
- It should be used to collect information about rawmidi devices without
- exclusive lock.
-
-\layout Subsubsection*
-
-int snd_ctl_rawmidi_output_switches(void *handle)
-\layout Standard
-
-Returns count of rawmidi output switches.
- In this context 'switch' means universal control interface between kernel
- and application which allows various types of control.
- Function returns count if successful, otherwise it returns an error code.
- Return value should be zero if sound card doesn't have any control switch.
-\layout Subsubsection*
-
-int snd_ctl_rawmidi_output_switch(void *handle, const char *switch_id)
-\layout Standard
-
-Returns index for switch with name
-\shape italic
-switch_id
-\shape default
-.
- Function returns switch index if successful, otherwise it returns an error
- code.
- Return value should be zero if sound card doesn't have any rawmidi output
- switch.
-\layout Subsubsection*
-
-int snd_ctl_rawmidi_output_switch_read(void *handle\i \c{ }
- int switchn\i \c{ }
- snd_rawmidi_swit
-ch_t *data)
-\layout Standard
-
-Fills the
-\shape italic
-*data
-\shape default
- structure with data about switch with index
-\shape italic
-switchn
-\shape default
-.
- Function returns zero if successful, otherwise it returns an error code.
- Details about the
-\shape italic
-snd_rawmidi_switch_t
-\shape default
- structure are in the
-\series bold
-RawMidi Interface
-\series default
- section.
-\layout Subsubsection*
-
-int snd_ctl_rawmidi_output_switch_write(void *handle\i \c{ }
- int switchn\i \c{ }
- snd_rawmidi_swi
-tch_t *data)
-\layout Standard
-
-Writes the
-\shape italic
-*data
-\shape default
- structure with data about switch with index
-\shape italic
-switchn
-\shape default
- to kernel.
- Function returns zero if successful, otherwise it returns an error code.
- Details about the
-\shape italic
-snd_rawmidi_switch_t
-\shape default
- structure are in the
-\series bold
-RawMidi Interface
-\series default
- section.
-\layout Subsubsection*
-
-int snd_ctl_rawmidi_input_info(void *handle, int dev, snd_rawmidi_input_info_t
- *info)
-\layout Standard
-
-Fills the
-\shape italic
-*info
-\shape default
- structure with data about the rawmidi device and input direction.
- Function returns zero if successful, otherwise it returns an error code.
- Details about the
-\shape italic
-snd_rawmidi_record_info_t
-\shape default
- structure are in the
-\series bold
-RawMidi Interface
-\series default
- section.
- The argument
-\shape italic
-dev
-\shape default
- selects the device number for the sound card referenced by
-\shape italic
-*handle
-\shape default
-.
- Its range is 0 to N where N is
-\shape italic
-struct snd_ctl_hw_info->pcmdevs - 1
-\shape default
-.
- This function will work if the selected rawmidi device is busy, too.
- It should be used to collect information about rawmidi devices without
- exclusive lock.
-
-\layout Subsubsection*
-
-int snd_ctl_rawmidi_input_switches(void *handle)
-\layout Standard
-
-Returns count of rawmidi input switches.
- In this context 'switch' means universal control interface between kernel
- and application which allows various types of control.
- Function returns count if successful, otherwise it returns an error code.
- Return value should be zero if sound card doesn't have any rawmidi input
- switch.
-\layout Subsubsection*
-
-int snd_ctl_rawmidi_input_switch(void *handle, const char *switch_id)
-\layout Standard
-
-Returns index for switch with name
-\shape italic
-switch_id
-\shape default
-.
- Function returns switch index if successful, otherwise it returns an error
- code.
-\layout Subsubsection*
-
-int snd_ctl_rawmidi_input_switch_read(void *handle\i \c{ }
- int switchn\i \c{ }
- snd_pcm_switch_t
- *data)
-\layout Standard
-
-Fills the
-\shape italic
-*data
-\shape default
- structure with data about switch with index
-\shape italic
-switchn
-\shape default
-.
- Function returns zero if successful, otherwise it returns an error code.
- Details about the
-\shape italic
-snd_rawmidi_switch_t
-\shape default
- structure are in the
-\series bold
-RawMidi Interface
-\series default
- Interface section.
-\layout Subsubsection*
-
-int snd_ctl_rawmidi_input_switch_write(void *handle\i \c{ }
- int switchn\i \c{ }
- snd_pcm_switch_t
- *data)
-\layout Standard
-
-Writes the
-\shape italic
-*data
-\shape default
- structure with data about switch with index
-\shape italic
-switchn
-\shape default
- to kernel.
- Function returns zero if successful, otherwise it returns an error code.
- Details about the
-\shape italic
-snd_rawmidi_switch_t
-\shape default
- structure are in the
-\series bold
-RawMidi Interface
-\series default
- section.
-\layout Subsubsection
-
-Examples
-\layout Standard
-
-The following example shows how all PCM devices can be detected for the
- first sound card (#0) in the system.
-\layout LyX-Code
-
-int card = 0, err;
-\layout LyX-Code
-
-void *handle;
-\layout LyX-Code
-
-snd_ctl_hw_info_t info;
-\newline
-
-\layout LyX-Code
-
-if ((err = snd_ctl_open(&handle, card)) < 0) {
-\layout LyX-Code
-
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
- fprintf(stderr, "open failed: %s
-\backslash
-n", snd_strerror(err));
-\layout LyX-Code
-
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
- return;
-\layout LyX-Code
-
-}
-\layout LyX-Code
-
-if ((err = snd_ctl_hw_info(handle, &info)) < 0) {
-\layout LyX-Code
-
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
- fprintf(stderr, "hw info failed: %s
-\backslash
-n",
-\layout LyX-Code
-
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
- snd_strerror(err));
-\layout LyX-Code
-
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
- snd_ctl_close(handle);
-\layout LyX-Code
-
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-return;
-\layout LyX-Code
-
-}
-\layout LyX-Code
-
-printf("Installed PCM devices for card #i: %i
-\backslash
-n",
-\layout LyX-Code
-
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
- card + 1, info.pcmdevs);
-\layout LyX-Code
-
-snd_ctl_close(handle);
-\layout Section
-
-Mixer Interface
-\layout Standard
-
-The Mixer Interface allows applications to change the volume level of a
- sound card's input/output channels in both the linear range\i \c{ }
- percentage
- range (0-100) and in decibels.
- It also supports features like hardware mute, input sound source, stereo
- signal routing etc.
-\layout Subsection
-
-Low-Level Layer
-\layout Standard
-
-Mixer devices aren't opened exclusively.
- This allows applications to open a device multiple times with one or more
- processes.
-\layout Subsubsection*
-
-int snd_mixer_open(void **handle, int card, int device)
-\layout Standard
-
-Creates new handle and opens a connection to the kernel sound mixer interface
- for sound card number
-\shape italic
-card
-\shape default
- (0-N) and mixer device number
-\shape italic
-device
-\shape default
-.
- Also checks if protocol is compatible to prevent use of old programs with
- new kernel API.
- Function returns zero if successful, otherwise it returns an error code.
-\layout Subsubsection*
-
-int snd_mixer_close(void *handle)
-\layout Standard
-
-Frees all resources allocated to the mixer handle and closes its connection
- to the kernel sound mixer interface.
- Function returns zero if successful, otherwise it returns an error code.
-\layout Subsubsection*
-
-int snd_mixer_file_descriptor(void *handle)
-\layout Standard
-
-Returns the file descriptor for the connection to the kernel sound mixer
- interface.
- This function should be used only in very special cases.
- Function returns a negative error code if an error was encountered.
-\layout Standard
-
-The file descriptor should be used for the
-\shape italic
-select(2)
-\shape default
- synchronous multiplexer function for determining read direction.
- Applications should call
-\shape italic
-snd_mixer_read()
-\shape default
- function if some data is waiting to be read.
- It is recommended that you do this, since it leaves place for this function
- to handle some new kernel API specifications.
-\layout Subsubsection*
-
-int snd_mixer_channels(void *handle)
-\layout Standard
-
-Returns the count of mixer channels for appropriate mixer device, otherwise
- the return value is negative, and signifies an error code.
- Never returns zero.
-\layout Subsubsection*
-
-int snd_mixer_info(void *handle, snd_mixer_info_t *info)
-\layout Standard
-
-Fills the
-\shape italic
-*info
-\shape default
- structure with information about the mixer associated with
-\shape italic
-*handle
-\shape default
-.
- Returns zero if successful, otherwise it returns an error code.
-\layout LyX-Code
-
-
-\shape italic
-/* mixer can do only exclusive record */
-\layout LyX-Code
-
-#define SND_MIXER_INFO_CAP_EXCL_RECORD
-\protected_separator
- 0x00000001
-\layout Standard
-
-
-\protected_separator
-
-\layout LyX-Code
-
-struct snd_mixer_info {
-\layout LyX-Code
-
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\shape italic
-/* type of sound card - SND_CARD_TYPE_XXXX */
-\layout LyX-Code
-
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
- unsigned int type;
-\layout LyX-Code
-
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\shape italic
-/* count of mixer devices */
-\layout LyX-Code
-
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-unsigned int channels;
-\layout LyX-Code
-
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\shape italic
-/* some flags about this device (SND_MIXER_INFO_CAP_XXXX) */
-\layout LyX-Code
-
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
- unsigned int caps;
-\layout LyX-Code
-
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\shape italic
-/* ID of this mixer */
-\layout LyX-Code
-
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
- unsigned char id[32];
-\layout LyX-Code
-
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\shape italic
-/* name of this device */
-\layout LyX-Code
-
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
- unsigned char name[80];
-\layout LyX-Code
-
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\shape italic
-/* reserved for future use */
-\layout LyX-Code
-
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
- char reserved[ 32 ];
-\layout LyX-Code
-
-};
-\layout Subsubsection*
-
-int snd_mixer_switches(void *handle)
-\layout Standard
-
-Returns count of mixer switches.
- In this context 'switch' means universal control interface between kernel
- and application which allows various types of control.
- Function returns count if successful, otherwise it returns an error code.
- Return value will be zero if sound card doesn't have any mixer switch.
-\layout Subsubsection*
-
-int snd_mixer_switch(void *handle, const char *switch_id)
-\layout Standard
-
-Returns index for switch with name
-\shape italic
-switch_id
-\shape default
-.
- Function returns switch index if successful, otherwise it returns an error
- code.
-\layout Subsubsection*
-
-int snd_mixer_switch_read(void *handle\i \c{ }
- int switchn\i \c{ }
- snd_mixer_switch_t *data)
-\layout Standard
-
-Fills the
-\shape italic
-*data
-\shape default
- structure with data about switch with index
-\shape italic
-switchn
-\shape default
-.
- Function returns zero if successful, otherwise it returns an error code.
-\layout LyX-Code
-
-
-\shape italic
-/* 0 or 1 (enable member of union) */
-\layout LyX-Code
-
-#define SND_MIXER_SW_TYPE_BOOLEAN
-\protected_separator
-
-\protected_separator
- 0
-\layout LyX-Code
-
-
-\shape italic
-/* 0 to 255 - from low to high (data8[0] member of union) */
-\layout LyX-Code
-
-#define SND_MIXER_SW_TYPE_BYTE
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-1
-\layout LyX-Code
-
-
-\shape italic
-/* 0 to 65535 - from low to high (data16[0] member of union) */
-\layout LyX-Code
-
-#define SND_MIXER_SW_TYPE_WORD
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-2
-\layout LyX-Code
-
-
-\shape italic
-/* 0 to 4294967296 \i \={ }
- from low to high (data32[0] member of union) */
-\layout LyX-Code
-
-#define SND_MIXER_SW_TYPE_DWORD
-\protected_separator
-
-\protected_separator
-
-\protected_separator
- 3
-\layout LyX-Code
-
-
-\shape italic
-/* user type - no type control */
-\layout LyX-Code
-
-#define SND_MIXER_SW_TYPE_USER
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-(~0)
-\layout Standard
-
-
-\protected_separator
-
-\layout LyX-Code
-
-
-\shape italic
-/* well known (named) switches */
-\layout LyX-Code
-
-#define SND_MIXER_SW_LOUDNESS
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
- "Loudness"
-\protected_separator
-
-\shape italic
-/* bass boost */
-\layout LyX-Code
-
-#define SND_MIXER_SW_SIM_STEREO
-\protected_separator
-
-\protected_separator
-
-\protected_separator
- "Simulated Stereo Enhancement"
-\layout LyX-Code
-
-#define SND_MIXER_SW_3D
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
- "3D Stereo Enhancement"
-\layout LyX-Code
-
-
-\shape italic
-/* microphone gain */
-\layout LyX-Code
-
-#define SND_MIXER_SW_MIC_GAIN
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
- "MIC Gain"
-\layout LyX-Code
-
-
-\shape italic
-/* microphone auto gain control */
-\layout LyX-Code
-
-#define SND_MIXER_SW_MIC_GAIN
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
- "MIC Auto-Gain-Control"
-\layout LyX-Code
-
-
-\shape italic
-/* change microphone impedance */
-\layout LyX-Code
-
-#define SND_MIXER_SW_MIC_GAIN
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
- "Change MIC Impedance"
-\layout LyX-Code
-
-
-\shape italic
-/* change line-in to output */
-\layout LyX-Code
-
-#define SND_MIXER_SW_MIC_GAIN
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
- "Line In to Output"
-\layout LyX-Code
-
-#define SND_MIXER_SW_IEC958OUT
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
- "IEC-958 (S/PDIF) Output"
-\layout LyX-Code
-
-#define SND_MIXER_SW_IEC958IN
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
- "IEC-958 (S/PDIF) Input"
-\layout Standard
-
-
-\protected_separator
-
-\layout LyX-Code
-
-struct snd_mixer_switch {
-\layout LyX-Code
-
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\shape italic
-/* switch index (filled by application) */
-\layout LyX-Code
-
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
- unsigned int switchn;
-\layout LyX-Code
-
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\shape italic
-/* identification of switch (for driver) */
-\layout LyX-Code
-
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
- unsigned char name[32];
-\layout LyX-Code
-
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\shape italic
-/* type of switch value \i \={ }
- See SND_CTL_SW_TYPE_XXXX */
-\layout LyX-Code
-
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
- unsigned int type;
-\layout LyX-Code
-
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\shape italic
-/* low range value */
-\layout LyX-Code
-
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
- unsigned int low;
-\layout LyX-Code
-
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\shape italic
-/* high range value */
-\layout LyX-Code
-
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
- unsigned int high;
-\layout LyX-Code
-
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
- union {
-\layout LyX-Code
-
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
- unsigned int enable;
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\shape italic
-/* 0 = off\i \c{ }
- 1 = on */
-\layout LyX-Code
-
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
- unsigned char data8[32];
-\protected_separator
-
-\protected_separator
-
-\shape italic
-/* 8-bit data */
-\layout LyX-Code
-
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
- unsigned short data16[16];
-\protected_separator
-
-\shape italic
-/* 16-bit data */
-\layout LyX-Code
-
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
- unsigned int data32[8];
-\protected_separator
-
-\protected_separator
-
-\shape italic
-/* 32-bit data */
-\layout LyX-Code
-
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
- } value;
-\layout LyX-Code
-
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\shape italic
-/* reserved for future use \i \={ }
- must be zero !!! */
-\layout LyX-Code
-
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
- unsigned char reserved[32];
-\layout LyX-Code
-
-}
-\layout Subsubsection*
-
-int snd_mixer_switch_write(void *handle\i \c{ }
- int switchn\i \c{ }
- snd_mixer_switch_t *data)
-\layout Standard
-
-Writes the
-\shape italic
-*data
-\shape default
- structure with data about switch with index
-\shape italic
-switchn
-\shape default
- to kernel.
- Function returns zero if successful, otherwise it returns an error code.
-
-\layout Subsubsection*
-
-int snd_mixer_exact_mode(void *handle, int enable)
-\layout Standard
-
-Turns on = 1 or off = 0 (by default) exact mode.
- This mode allows application to set/get volume values in exact range which
- uses hardware.
- In non-exact mode range is always from percentage 0 to 100 and driver does
- conversion to hardware range.
- Function returns zero if successful, otherwise it returns an error code.
-\layout Subsubsection*
-
-int snd_mixer_channel(void *handle, const char *channel_id)
-\layout Standard
-
-Returns the channel number (index) associated with
-\shape italic
-channel_id
-\shape default
- (channel name), or returns an error code.
- Note: Below mixer channel IDs are subject to change and will be extended
- if new hardware has support for other mixer input/output channels.
-\layout LyX-Code
-
-#define SND_MIXER_ID_MASTER
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-"Master"
-\layout LyX-Code
-
-#define SND_MIXER_ID_MASTER1
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-"Master 1"
-\layout LyX-Code
-
-
-\shape italic
-/* digital master */
-\layout LyX-Code
-
-#define SND_MIXER_ID_MASTERD
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-"Master D"
-\layout LyX-Code
-
-
-\shape italic
-/* second digital master */
-\layout LyX-Code
-
-#define SND_MIXER_ID_MASTERD1
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-"Master D1"
-\layout LyX-Code
-
-#define SND_MIXER_ID_HEADPHONE
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-"Headphone"
-\layout LyX-Code
-
-#define SND_MIXER_ID_MASTER_MONO
-\protected_separator
-
-\protected_separator
-"Master M"
-\layout LyX-Code
-
-#define SND_MIXER_ID_3D
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-"3D Wide"
-\layout LyX-Code
-
-#define SND_MIXER_ID_3D_VOLUME
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-"3D Volume"
-\layout LyX-Code
-
-#define SND_MIXER_ID_3D_CENTER
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-"3D Center"
-\layout LyX-Code
-
-#define SND_MIXER_ID_3D_SPACE
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-"3D Space"
-\layout LyX-Code
-
-#define SND_MIXER_ID_3D_DEPTH
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-"3D Depth"
-\layout LyX-Code
-
-#define SND_MIXER_ID_BASS
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-"Bass"
-\layout LyX-Code
-
-#define SND_MIXER_ID_TREBLE
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-"Treble"
-\layout LyX-Code
-
-#define SND_MIXER_ID_FADER
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
- "Fader"
-\layout LyX-Code
-
-#define SND_MIXER_ID_SYNTHESIZER
-\protected_separator
- "Synth"
-\layout LyX-Code
-
-#define SND_MIXER_ID_SYNTHESIZER1
-\protected_separator
-"Synth 1"
-\layout LyX-Code
-
-#define SND_MIXER_ID_FM
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-"FM"
-\layout LyX-Code
-
-#define SND_MIXER_ID_EFFECT
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-"Effect"
-\layout LyX-Code
-
-#define SND_MIXER_ID_DSP
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-"DSP"
-\layout LyX-Code
-
-#define SND_MIXER_ID_PCM
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
- "PCM"
-\layout LyX-Code
-
-#define SND_MIXER_ID_PCM1
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-"PCM 1"
-\layout LyX-Code
-
-#define SND_MIXER_ID_LINE
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-"Line-In"
-\layout LyX-Code
-
-#define SND_MIXER_ID_MIC
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
- "MIC"
-\layout LyX-Code
-
-#define SND_MIXER_ID_CD
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-"CD"
-\layout LyX-Code
-
-#define SND_MIXER_ID_VIDEO
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-"Video"
-\layout LyX-Code
-
-#define SND_MIXER_ID_PHONE
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-"Phone"
-\layout LyX-Code
-
-#define SND_MIXER_ID_GAIN
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-"Record-Gain"
-\layout LyX-Code
-
-#define SND_MIXER_ID_MIC_GAIN
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-"Mic-Gain"
-\layout LyX-Code
-
-#define SND_MIXER_ID_IGAIN
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
- "In-Gain"
-\layout LyX-Code
-
-#define SND_MIXER_ID_OGAIN
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
- "Out-Gain"
-\layout LyX-Code
-
-#define SND_MIXER_ID_LOOPBACK
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-"Loopback"
-\layout LyX-Code
-
-#define SND_MIXER_ID_SPEAKER
-\protected_separator
-
-\protected_separator
-
-\protected_separator
- "PC Speaker"
-\layout LyX-Code
-
-#define SND_MIXER_ID_MONO
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
- "Mono"
-\layout LyX-Code
-
-#define SND_MIXER_ID_MONO1
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-"Mono 1"
-\layout LyX-Code
-
-#define SND_MIXER_ID_MONO2
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-"Mono 2"
-\layout LyX-Code
-
-#define SND_MIXER_ID_AUXA
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-"Aux A"
-\layout LyX-Code
-
-#define SND_MIXER_ID_AUXB
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-"Aux B"
-\layout LyX-Code
-
-#define SND_MIXER_ID_AUXC
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-"Aux C"
-\layout Subsubsection*
-
-int snd_mixer_channel_info(void *handle, int channel, snd_mixer_channel_info_t
- *info)
-\layout Standard
-
-Fills the
-\shape italic
-*info
-\shape default
- structure.
- The argument
-\shape italic
-channel
-\shape default
- specifies channel (0 to N) for which is the info requested.
- Function returns zero if successful, otherwise it returns an error code.
-\layout LyX-Code
-
-
-\shape italic
-/* mixer channel is record source */
-\layout LyX-Code
-
-#define SND_MIXER_CINFO_CAP_RECORD
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
- 0x00000001
-\layout LyX-Code
-
-
-\shape italic
-/* mixer channel is stereo */
-\layout LyX-Code
-
-#define SND_MIXER_CINFO_CAP_STEREO
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
- 0x00000002
-\layout LyX-Code
-
-
-\shape italic
-/* always set at this moment\i \c{ }
- driver emulates mute */
-\layout LyX-Code
-
-#define SND_MIXER_CINFO_CAP_MUTE
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
- 0x00000004
-\layout LyX-Code
-
-
-\shape italic
-/* channel supports hardware mute */
-\layout LyX-Code
-
-#define SND_MIXER_CINFO_CAP_HWMUTE
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
- 0x00000008
-\layout LyX-Code
-
-
-\shape italic
-/* channel does digital (not analog) mixing */
-\layout LyX-Code
-
-#define SND_MIXER_CINFO_CAP_DIGITAL
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-0x00000010
-\layout LyX-Code
-
-
-\shape italic
-/* external input channel */
-\layout LyX-Code
-
-#define SND_MIXER_CINFO_CAP_INPUT
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-0x00000020
-\layout LyX-Code
-
-
-\shape italic
-/* join mute is supported only */
-\layout LyX-Code
-
-
-\shape italic
-/* left and right channel doesn't have separate mute control */
-\layout LyX-Code
-
-#define SND_MIXER_CINFO_CAP_JOINMUTE
-\protected_separator
-
-\protected_separator
-
-\protected_separator
- 0x00000040
-\layout LyX-Code
-
-
-\shape italic
-/* join record is supported only *
-\layout LyX-Code
-
-
-\shape italic
-/* left and right channel doesn't have separate record control */
-\layout LyX-Code
-
-#define SND_MIXER_CINFO_CAP_JOINRECORD
-\protected_separator
-
-\protected_separator
- 0x00000080
-\layout LyX-Code
-
-
-\shape italic
-/* route left input to right output is supported */
-\layout LyX-Code
-
-#define SND_MIXER_CINFO_CAP_LTOR_OUT
-\protected_separator
-
-\protected_separator
-
-\protected_separator
- 0x00000100
-\layout LyX-Code
-
-
-\shape italic
-/* route right input to left output is supported */
-\layout LyX-Code
-
-#define SND_MIXER_CINFO_CAP_RTOL_OUT
-\protected_separator
-
-\protected_separator
-
-\protected_separator
- 0x00000200
-\layout LyX-Code
-
-
-\shape italic
-/* route left input to right ADC is supported */
-\layout LyX-Code
-
-#define SND_MIXER_CINFO_CAP_LTOR_IN
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-0x00000400
-\layout LyX-Code
-
-
-\shape italic
-/* route right input to left ADC is supported */
-\layout LyX-Code
-
-#define SND_MIXER_CINFO_CAP_RTOL_IN
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-0x00000800
-\layout LyX-Code
-
-
-\shape italic
-/* output route is only switch (cannot be used separately) */
-\layout LyX-Code
-
-#define SND_MIXER_CINFO_CAP_SWITCH_OUT
-\protected_separator
-
-\protected_separator
- 0x00001000
-\layout LyX-Code
-
-
-\shape italic
-/* input route is only switch (cannot be used separately) */
-\layout LyX-Code
-
-#define SND_MIXER_CINFO_CAP_SWITCH_IN
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-0x00002000
-\layout LyX-Code
-
-
-\shape italic
-/* data can be recorded even if output path is muted */
-\layout LyX-Code
-
-
-\shape italic
-/* (to avoid loopback) */
-\layout LyX-Code
-
-#define SND_MIXER_CINFO_CAP_RECORDBYMUTE
-\protected_separator
- 0x00004000
-\layout Standard
-
-
-\protected_separator
-
-\layout LyX-Code
-
-struct snd_mixer_channel_info {
-\layout LyX-Code
-
-
-\shape italic
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
- /* channel index (filled by application) */
-\layout LyX-Code
-
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
- unsigned int channel;
-\layout LyX-Code
-
-
-\shape italic
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
- /* parent channel # or SND_MIXER_PARENT */
-\layout LyX-Code
-
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
- unsigned int parent;
-\layout LyX-Code
-
-
-\shape italic
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
- /* name of this device */
-\layout LyX-Code
-
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
- unsigned char name[12];
-\layout LyX-Code
-
-
-\shape italic
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
- /* some flags about this device (SND_MIXER_CINFO_XXXX) */
-\layout LyX-Code
-
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
- unsigned int caps;
-\layout LyX-Code
-
-
-\shape italic
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
- /* min.
- value when exact mode (or always 0) */
-\layout LyX-Code
-
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
- int min;
-\layout LyX-Code
-
-
-\shape italic
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
- /* max.
- value when exact mode (or always 100) */
-\layout LyX-Code
-
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
- int max;
-\layout LyX-Code
-
-
-\shape italic
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
- /* minimum decibel value (*100) */
-\layout LyX-Code
-
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
- int min_dB;
-\layout LyX-Code
-
-
-\shape italic
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
- /* maximum decibel value (*100) */
-\layout LyX-Code
-
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
- int max_dB;
-\layout LyX-Code
-
-
-\shape italic
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
- /* step decibel value (*100) */
-\layout LyX-Code
-
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
- int step_dB;
-\layout LyX-Code
-
-
-\shape italic
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
- /* reserved for future use */
-\layout LyX-Code
-
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
- unsigned char reserved[16];
-\layout LyX-Code
-
-};
-\layout Subsubsection*
-
-int snd_mixer_channel_read(void *handle, int channel, snd_mixer_channel_t
- *data)
-\layout Standard
-
-Fills the
-\shape italic
-*data
-\shape default
- structure.
- The argument
-\shape italic
-channel
-\shape default
- specifies the channel (0 to N) for which is data requested.
- Function returns zero if successful, otherwise it returns an error code.
-\layout LyX-Code
-
-/* channel record source flags */
-\layout LyX-Code
-
-#define SND_MIXER_FLG_RECORD_LEFT
-\protected_separator
- 0x00000001
-\layout LyX-Code
-
-#define SND_MIXER_FLG_RECORD_RIGHT 0x00000002
-\layout LyX-Code
-
-#define SND_MIXER_FLG_RECORD
-\protected_separator
-
-\protected_separator
-
-\protected_separator
- 0x00000003
-\layout LyX-Code
-
-/* mute channel flags */
-\layout LyX-Code
-
-#define SND_MIXER_FLG_MUTE_LEFT
-\protected_separator
-
-\protected_separator
-0x00010000
-\layout LyX-Code
-
-#define SND_MIXER_FLG_MUTE_RIGHT
-\protected_separator
- 0x00020000
-\layout LyX-Code
-
-#define SND_MIXER_FLG_MUTE
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
- 0x00030000
-\layout LyX-Code
-
-/* input to output route setup */
-\layout LyX-Code
-
-#define SND_MIXER_FLG_LTOR_OUT
-\protected_separator
-
-\protected_separator
- 0x00100000
-\layout LyX-Code
-
-#define SND_MIXER_FLG_RTOL_OUT
-\protected_separator
-
-\protected_separator
- 0x00200000
-\layout LyX-Code
-
-#define SND_MIXER_FLG_SWITCH_OUT
-\protected_separator
- 0x00300000
-\layout LyX-Code
-
-/* input to ADC route setup */
-\layout LyX-Code
-
-#define SND_MIXER_FLG_LTOR_IN
-\protected_separator
-
-\protected_separator
-
-\protected_separator
- 0x00400000
-\layout LyX-Code
-
-#define SND_MIXER_FLG_RTOL_IN
-\protected_separator
-
-\protected_separator
-
-\protected_separator
- 0x00800000
-\layout LyX-Code
-
-#define SND_MIXER_FLG_SWITCH_IN
-\protected_separator
-
-\protected_separator
- 0x00c00000
-\layout LyX-Code
-
-/* set volume in decibels from dB variables */
-\layout LyX-Code
-
-#define SND_MIXER_FLG_DECIBEL
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-0x40000000
-\layout LyX-Code
-
-/* reserved for kernel use, don't use this flag from application */
-\layout LyX-Code
-
-#define SND_MIXER_FLG_FORCE
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-0x80000000
-\layout Standard
-
-
-\protected_separator
-
-\layout LyX-Code
-
-struct snd_mixer_channel {
-\layout LyX-Code
-
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
- /* channel # (filled by application) */
-\layout LyX-Code
-
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
- unsigned int channel;
-\layout LyX-Code
-
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
- /* some flags to read/write (SND_MIXER_FLG_XXXX) */
-\layout LyX-Code
-
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
- unsigned int flags;
-\layout LyX-Code
-
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
- /* min - max when exact mode (or 0 - 100) */
-\layout LyX-Code
-
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
- int left;
-\layout LyX-Code
-
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
- /* min - max when exact mode (or 0 - 100) */
-\layout LyX-Code
-
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
- int right;
-\layout LyX-Code
-
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
- /* dB * 100 */
-\layout LyX-Code
-
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
- int left_dB;
-\layout LyX-Code
-
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
- /* dB * 100 */
-\layout LyX-Code
-
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
- int right_dB;
-\layout LyX-Code
-
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
- unsigned char reserved[16];
-\layout LyX-Code
-
-};
-\layout Subsubsection*
-
-int snd_mixer_channel_write(void *handle, int channel, snd_mixer_channel_t
- *data)
-\layout Standard
-
-Writes the
-\shape italic
-*data
-\shape default
- structure to kernel.
- The
-\shape italic
-channel
-\shape default
- argument specifies the channel (0 to N) for which is data is to be applied.
- Function returns zero if successful, otherwise it returns an error code.
- This functions is the opposite of
-\shape italic
-snd_mixer_channel_read
-\shape default
-.
-\layout Subsubsection*
-
-int snd_mixer_read(void *handle, snd_mixer_callbacks_t *callbacks)
-\layout Standard
-
-This function reads and parses data from driver.
- Parsed actions are returned back to the application using the
-\shape italic
-callbacks
-\shape default
- structure.
- Applications should not parse data from the driver in standard cases.
- This function returns immediately after all data is read from driver.
- Does not block process.
-\layout LyX-Code
-
-typedef struct snd_mixer_callbacks {
-\layout LyX-Code
-
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
- /* should be used by application */
-\layout LyX-Code
-
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
- void *private_data;
-\layout LyX-Code
-
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
- void (*channel_was_changed)(void *private_data, int channel);
-\layout LyX-Code
-
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
- void (*switch_was_changed)(void *private_data,
-\protected_separator
-int switchn);
-\layout LyX-Code
-
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
- /* reserved for future use - must be NULL!!! */
-\layout LyX-Code
-
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
- void *reserved[14];
-\layout LyX-Code
-
-} snd_mixer_callbacks_t;
-\layout Subsubsection
-
-Examples
-\layout Standard
-
-The following example shows installed mixer channels for sound card #0 and
- mixer device #0 in the system, and also sets the master volume (if present)
- to 50.
-\layout LyX-Code
-
-int card = 0, device = 0, err;
-\layout LyX-Code
-
-void *handle;
-\layout LyX-Code
-
-snd_mixer_info_t info;
-\layout LyX-Code
-
-snd_mixer_channel_t channel;
-\layout Standard
-
-
-\protected_separator
-
-\layout LyX-Code
-
-if ((err = snd_mixer_open(&handle, card, device)) < 0) {
-\layout LyX-Code
-
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
- fprintf(stderr, "open failed: %s
-\backslash
-n", snd_strerror(err));
-\layout LyX-Code
-
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
- return;
-\layout LyX-Code
-
-}
-\layout LyX-Code
-
-if ((err = snd_mixer_info(handle, &info)) < 0) {
-\layout LyX-Code
-
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
- fprintf(stderr, "info failed: %s
-\backslash
-n", snd_strerror(err));
-\layout LyX-Code
-
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
- snd_mixer_close(handle);
-\layout LyX-Code
-
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
- return;
-\layout LyX-Code
-
-}
-\layout LyX-Code
-
-printf("Installed MIXER channels for card #i and device %i: %i
-\backslash
-n",
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
- card + 1, device,
-\layout LyX-Code
-
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
- info.channels);
-\layout LyX-Code
-
-master = snd_mixer_channel(handle, SND_MIXER_ID_MASTER);
-\layout LyX-Code
-
-if (master >= 0) {
-\layout LyX-Code
-
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
- if ((err = snd_mixer_read(handle, master, &channel)) < 0) {
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
- fprintf(stderr, "master read failed: %s
-\backslash
-n",
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
- snd_strerror( err ));
-\layout LyX-Code
-
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
- snd_mixer_close( handle );
-\layout LyX-Code
-
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
- return;
-\layout LyX-Code
-
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
- }
-\layout LyX-Code
-
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
- channel.left = channel.right = 50;
-\layout LyX-Code
-
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
- if ((err = snd_mixer_write(handle, master, &channel)) < 0 ) {
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
- fprintf(stderr, "master write failed: %s
-\backslash
-n",
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
- snd_strerror( err ));
-\layout LyX-Code
-
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
- snd_mixer_close(handle);
-\layout LyX-Code
-
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
- return;
-\layout LyX-Code
-
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
- }
-\layout LyX-Code
-
-}
-\layout LyX-Code
-
-snd_mixer_close(handle);
-\layout Section
-
-Digital Audio (PCM) Interface
-\layout Standard
-
-Digital audio is the most commonly used method of representing sound inside
- a computer.
- In this method sound is stored as a sequence of samples taken from the
- audio signal using constant time intervals.
- A sample represents volume of the signal at the moment when it was measured.
- In uncompressed digital audio each sample require one or more bytes of
- storage.
- The number of bytes required depends on number of channels (mono, stereo)
- and sample format (8 or 16 bits, mu-Law, etc.).
- The length of this interval determines the sampling rate.
- Commonly used sampling rates are between 8 kHz (telephone quality) and
- 48 kHz (DAT tapes).
-\layout Standard
-
-The physical devices used in digital audio are called the ADC (Analog to
- Digital Converter) and DAC (Digital to Analog Converter).
- A device containing both ADC and DAC is commonly known as a codec.
- The codec device used in a Sound Blaster cards is called a DSP which is
- somewhat misleading since DSP also stands for Digital Signal Processor
- (the SB DSP chip is very limited when compared to "true" DSP chips).
-\layout Standard
-
-Sampling parameters affect the quality of sound which can be reproduced
- from the recorded signal.
- The most fundamental parameter is sampling rate which limits the highest
- frequency that can be stored.
- It is well known (Nyquist's Sampling Theorem) that the highest frequency
- that can be stored in a sampled signal is at most 1/2 of the sampling frequency.
- For example, an 8 kHz sampling rate permits the recording of a signal in
- which the highest frequency is less than 4 kHz.
- Higher frequency signals must be filtered out before feeding them to DAC.
-\layout Standard
-
-Sample encoding limits the dynamic range of a recorded signal (difference
- between the faintest and the loudest signal that can be recorded).
- In theory the maximum dynamic range of signal is number_of_bits * 6 dB
- .
- This means that 8 bits sampling resolution gives dynamic range of 48 dB
- and 16 bit resolution gives 96 dB.
-\layout Standard
-
-Quality has price.
- The number of bytes required to store an audio sequence depends on sampling
- rate, number of channels and sampling resolution.
- For example just 8000 bytes of memory is required to store one second of
- sound using 8 kHz/8 bits/mono but 48 kHz/16bit/stereo takes 192 kilobytes.
- A 64 kbps ISDN channel is required to transfer a 8kHz/8bit/mono audio stream
- in real time, and about 1.5 Mbps is required for DAT quality (48kHz/16bit/stereo
-).
- On the other hand it is possible to store just 5.46 seconds of sound in
- a megabyte of memory when using 48kHz/16bit/stereo sampling.
- With 8kHz/8bits/mono it is possible to store 131 seconds of sound using
- the same amount of memory.
- It is possible to reduce memory and communication costs by compressing
- the recorded signal but this is beyond the scope of this document.
-
-\layout Subsection
-
-Low-Level Layer
-\layout Standard
-
-Audio devices are opened exclusively for a selected direction.
- This doesn't allow open from more than one processes for the same audio
- device in the same direction, but does allow one open call to each playback
- direction and second open call to record direction independently.
- Audio devices return EBUSY error to applications when other applications
- have already opened the requested direction.
-\layout Standard
-
-Low-Level layer supports these formats:
-\layout LyX-Code
-
-
-\shape italic
-/* muLaw compressed samples */
-\layout LyX-Code
-
-#define SND_PCM_SFMT_MU_LAW
-\protected_separator
-
-\protected_separator
-
-\protected_separator
- 0
-\layout LyX-Code
-
-
-\shape italic
-/* aLaw compressed samples */
-\layout LyX-Code
-
-#define SND_PCM_SFMT_A_LAW
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-1
-\layout LyX-Code
-
-
-\shape italic
-/* Ima-ADPM 4:1 compressed samples */
-\layout LyX-Code
-
-#define SND_PCM_SFMT_IMA_ADPCM
-\protected_separator
-
-\protected_separator
-2
-\layout LyX-Code
-
-
-\shape italic
-/* Unsigned 8-bit samples (most common 8-bit format) */
-\layout LyX-Code
-
-#define SND_PCM_SFMT_U8
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
- 3
-\layout LyX-Code
-
-
-\shape italic
-/* Signed 16-bit Little Endian samples (most common 16-bit format) */
-\layout LyX-Code
-
-#define SND_PCM_SFMT_S16_LE
-\protected_separator
-
-\protected_separator
-
-\protected_separator
- 4
-\layout LyX-Code
-
-
-\shape italic
-/* Signed 16-bit Big Endian samples */
-\layout LyX-Code
-
-#define SND_PCM_SFMT_S16_BE
-\protected_separator
-
-\protected_separator
-
-\protected_separator
- 5
-\layout LyX-Code
-
-
-\shape italic
-/* Signed 8-bit samples */
-\layout LyX-Code
-
-#define SND_PCM_SFMT_S8
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
- 6
-\layout LyX-Code
-
-
-\shape italic
-/* Unsigned 16-bit Little Endian samples */
-\layout LyX-Code
-
-#define SND_PCM_SFMT_U16_LE
-\protected_separator
-
-\protected_separator
-
-\protected_separator
- 7
-\layout LyX-Code
-
-
-\shape italic
-/* Unsigned 16-bit Big Endian samples */
-\layout LyX-Code
-
-#define SND_PCM_SFMT_U16_BE
-\protected_separator
-
-\protected_separator
-
-\protected_separator
- 8
-\layout LyX-Code
-
-
-\shape italic
-/* MPEG 1/2 stream */
-\layout LyX-Code
-
-#define SND_PCM_SFMT_MPEG
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
- 9
-\layout LyX-Code
-
-
-\shape italic
-/* GSM stream */
-\layout LyX-Code
-
-#define SND_PCM_SFMT_GSM
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-10
-\layout Standard
-
-
-\protected_separator
-
-\layout LyX-Code
-
-#define SND_PCM_FMT_MU_LAW
-\protected_separator
-
-\protected_separator
-
-\protected_separator
- (1 << SND_PCM_SFMT_MU_LAW)
-\layout LyX-Code
-
-#define SND_PCM_FMT_A_LAW
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-(1 << SND_PCM_SFMT_A_LAW)
-\layout LyX-Code
-
-#define SND_PCM_FMT_IMA_ADPCM
-\protected_separator
-
-\protected_separator
-(1 << SND_PCM_SFMT_IMA_ADPCM)
-\layout LyX-Code
-
-#define SND_PCM_FMT_U8
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
- (1 << SND_PCM_SFMT_U8)
-\layout LyX-Code
-
-#define SND_PCM_FMT_S16_LE
-\protected_separator
-
-\protected_separator
-
-\protected_separator
- (1 << SND_PCM_SFMT_S16_LE)
-\layout LyX-Code
-
-#define SND_PCM_FMT_S16_BE
-\protected_separator
-
-\protected_separator
-
-\protected_separator
- (1 << SND_PCM_SFMT_S16_BE)
-\layout LyX-Code
-
-#define SND_PCM_FMT_S8
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
- (1 << SND_PCM_SFMT_S8)
-\layout LyX-Code
-
-#define SND_PCM_FMT_U16_LE
-\protected_separator
-
-\protected_separator
-
-\protected_separator
- (1 << SND_PCM_SFMT_U16_LE)
-\layout LyX-Code
-
-#define SND_PCM_FMT_U16_BE
-\protected_separator
-
-\protected_separator
-
-\protected_separator
- (1 << SND_PCM_SFMT_U16_BE)
-\layout LyX-Code
-
-#define SND_PCM_FMT_MPEG
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
- (1 << SND_PCM_SFMT_MPEG)
-\layout LyX-Code
-
-#define SND_PCM_FMT_GSM
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-(1 << SND_PCM_SFMT_GSM)
-\layout Standard
-
-Constants with prefix
-\shape italic
-SND_PCM_FMT_
-\shape default
- are used in info structures and constants with prefix
-\shape italic
-SND_PCM_SFMT_
-\shape default
- are used in format structures.
-\layout Standard
-
-ALSA PCM API uses an enhanced double buffering scheme.
- This allows the user to implement a more comfortable buffer setup.
- Audio buffer is separated to small fragments.
- Each fragment has the same size.
- Application can set wakeup limits like
-\begin_inset Quotes eld
-\end_inset
-
-I want to get recorded data when at least two fragments with size 160 bytes
- are filled.
-\begin_inset Quotes erd
-\end_inset
-
-.
- For more information you should see description of
-\shape italic
-snd_pcm_*_params_t
-\shape default
- and
-\shape italic
-snd_pcm_*_status_t
-\shape default
- structures and the
-\emph on
-snd_pcm_playback_status(), snd_pcm_record_status()
-\emph default
-functions, documented below.
-\layout Subsubsection*
-
-int snd_pcm_open(void **handle, int card, int device, int mode)
-\layout Standard
-
-Creates a new handle and opens a connection to the kernel sound audio interface
- for sound card number
-\shape italic
-card
-\shape default
- (0-N) and audio device number
-\shape italic
-device
-\shape default
-.
- Function also checks if protocol is compatible to prevent use of old programs
- with a new kernel API.
- Function returns zero if successful otherwise it returns an error code.
- Error code -EBUSY is returned when some process owns the selected direction.
-\layout Standard
-
-Default format after opening is mono
-\shape italic
-mu-Law
-\shape default
- at 8000Hz.
- This device can be used directly for playback of standard .au (Sparc) files.
-
-\layout Standard
-
-The following modes should be used for the
-\shape italic
-mode
-\shape default
- argument:
-\layout LyX-Code
-
-#define SND_PCM_OPEN_PLAYBACK
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-(O_WRONLY)
-\layout LyX-Code
-
-#define SND_PCM_OPEN_RECORD
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-(O_RDONLY)
-\layout LyX-Code
-
-#define SND_PCM_OPEN_DUPLEX
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-(O_RDWR)
-\layout Subsubsection*
-
-int snd_pcm_close(void *handle)
-\layout Standard
-
-Frees all resources allocated with audio handle and closes the connection
- to the kernel sound audio interface.
- Function returns zero if successful, otherwise it returns an error code.
-\layout Subsubsection*
-
-int snd_pcm_file_descriptor(void *handle)
-\layout Standard
-
-Returns the file descriptor of the connection to the kernel sound audio
- interface.
- Function returns an error code if an error was encountered.
-\layout Standard
-
-The file descriptor should be used for the
-\shape italic
-select(2)
-\shape default
- synchronous multiplexer function for setting the read direction.
- Application should call
-\shape italic
-snd_pcm_read()
-\shape default
- or
-\shape italic
-snd_pcm_write()
-\shape default
- functions if data is waiting to be read or a write can be performed.
- Calling these functions is highly recommended, as it leaves a place for
- the API to do things like data conversions, if needed.
-\layout Subsubsection*
-
-int snd_pcm_block_mode(void *handle, int enable)
-\layout Standard
-
-Sets up block (default) or non-block mode for a handle.
- Block mode suspends execution of a program when
-\shape italic
-snd_pcm_read()
-\shape default
- or
-\shape italic
-snd_pcm_write()
-\shape default
- is called for the time which is needed for the actual playback or record
- over of the selected limit.
- In non-block mode, programs aren't suspended and the above functions return
- immediately with the count of bytes which were read or written by the driver.
- When used in this way, don't try to use the entire buffer after the call,
- but instead process the number of bytes returned, and call the function
- again.
-\layout Subsubsection*
-
-int snd_pcm_info(void *handle, snd_pcm_info_t *info)
-\layout Standard
-
-Fills the
-\shape italic
-*info
-\shape default
- structure with data about the PCM device selected by
-\shape italic
-*handle
-\shape default
-.
- Function returns zero if successful, otherwise it returns an error code.
-\layout LyX-Code
-
-
-\shape italic
-/* hardware have codec */
-\layout LyX-Code
-
-#define SND_PCM_INFO_CODEC
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-0x00000001
-\layout LyX-Code
-
-#define SND_PCM_INFO_DSP
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-SND_PCM_INFO_CODEC
-\layout LyX-Code
-
-
-\shape italic
-/* this flag is reserved and should be never used */
-\layout LyX-Code
-
-
-\shape italic
-/* It remains for compatibility with Open Sound System driver.
- */
-\layout LyX-Code
-
-#define SND_PCM_INFO_MMAP
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
- 0x00000002
-\layout LyX-Code
-
-
-\shape italic
-/* playback direction is supported */
-\layout LyX-Code
-
-#define SND_PCM_INFO_PLAYBACK
-\protected_separator
-
-\protected_separator
-
-\protected_separator
- 0x00000100
-\layout LyX-Code
-
-
-\shape italic
-/* record direction is supported */
-\layout LyX-Code
-
-#define SND_PCM_INFO_RECORD
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
- 0x00000200
-\layout LyX-Code
-
-#define SND_PCM_INFO_DUPLEX
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
- 0x00000400
-\layout LyX-Code
-
-
-\shape italic
-/* rate for playback & record must be same */
-\layout LyX-Code
-
-#define SND_PCM_INFO_DUPLEX_LIMIT
-\protected_separator
- 0x00000800
-\layout LyX-Code
-
-
-\shape italic
-/* duplex is supported only by mono (one channel) format */
-\layout LyX-Code
-
-#define SND_PCM_INFO_DUPLEX_MONO
-\protected_separator
-
-\protected_separator
-0x00001000
-\layout Standard
-
-
-\protected_separator
-
-\layout LyX-Code
-
-struct snd_pcm_info {
-\layout LyX-Code
-
-
-\shape italic
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
- /* sound card type */
-\layout LyX-Code
-
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
- unsigned int type;
-\layout LyX-Code
-
-
-\shape italic
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
- /* see SND_PCM_INFO_XXXX */
-\layout LyX-Code
-
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
- unsigned int flags;
-\layout LyX-Code
-
-
-\shape italic
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
- /* ID of this PCM device */
-\layout LyX-Code
-
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
- unsigned char id[32];
-\layout LyX-Code
-
-
-\shape italic
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
- /* name of this device */
-\layout LyX-Code
-
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
- unsigned char name[80];
-\layout LyX-Code
-
-
-\shape italic
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
- /* reserved for future use */
-\layout LyX-Code
-
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
- unsigned char reserved[64];
-\layout LyX-Code
-
-};
-\layout Subsubsection*
-
-int snd_pcm_playback_info(void *handle, snd_pcm_playback_info_t *info)
-\layout Standard
-
-Fills the *info structure with data about PCM playback.
- Function returns zero if successful, otherwise it returns an error code.
-\layout LyX-Code
-
-#define SND_PCM_PINFO_BATCH
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-0x00000001
-\layout LyX-Code
-
-#define SND_PCM_PINFO_8BITONLY
-\protected_separator
- 0x00000002
-\layout LyX-Code
-
-#define SND_PCM_PINFO_16BITONLY
-\protected_separator
-0x00000004
-\layout Standard
-
-
-\protected_separator
-
-\layout LyX-Code
-
-struct snd_pcm_playback_info {
-\layout LyX-Code
-
-
-\shape italic
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
- /* see SND_PCM_PINFO_XXXX */
-\layout LyX-Code
-
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
- unsigned int flags;
-\layout LyX-Code
-
-
-\shape italic
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
- /* supported formats */
-\layout LyX-Code
-
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
- unsigned int formats;
-\layout LyX-Code
-
-
-\shape italic
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
- /* min rate (in Hz) */
-\layout LyX-Code
-
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
- unsigned int min_rate;
-\layout LyX-Code
-
-
-\shape italic
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
- /* max rate (in Hz) */
-\layout LyX-Code
-
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
- unsigned int max_rate;
-\layout LyX-Code
-
-
-\shape italic
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
- /* min channels - voices (probably always 1) */
-\layout LyX-Code
-
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
- unsigned int min_channels;
-\layout LyX-Code
-
-
-\shape italic
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
- /* max channels - voices */
-\layout LyX-Code
-
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
- unsigned int max_channels;
-\layout LyX-Code
-
-
-\shape italic
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
- /* playback buffer size in bytes */
-\layout LyX-Code
-
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
- unsigned int buffer_size;
-\layout LyX-Code
-
-
-\shape italic
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
- /* min fragment size in bytes */
-\layout LyX-Code
-
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
- unsigned int min_fragment_size;
-\layout LyX-Code
-
-
-\shape italic
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
- /* max fragment size in bytes */
-\layout LyX-Code
-
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
- unsigned int max_fragment_size;
-\layout LyX-Code
-
-
-\shape italic
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
- /* align fragment value */
-\layout LyX-Code
-
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
- unsigned int fragment_align;
-\layout LyX-Code
-
-
-\shape italic
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
- /* supported formats directly by hardware */
-\layout LyX-Code
-
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
- unsigned int hw_formats;
-\layout LyX-Code
-
-
-\shape italic
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
- /* count of playback switches */
-\layout LyX-Code
-
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
- unsigned int switches;
-\layout LyX-Code
-
-
-\shape italic
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
- /* reserved for future use */
-\layout LyX-Code
-
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
- unsigned char reserved[56];
-\layout LyX-Code
-
-};
-\layout Description
-
-SND_PCM_PINFO_BATCH Driver implements double buffering with this device.
- This means that the chip used for data processing has its own memory, and
- output will be more delayed than if a traditional codec chip is used.
-\layout Description
-
-SND_PCM_PINFO_8BITONLY If this bit is set, the driver uses 8-bit format
- for 16-bit samples and does software conversion.
- This bit is set on broken SoundBlaster 16/AWE sound cards which can't do
- full 16-bit duplex.
- If this bit is set application or higher digital audio layer should do
- the conversion from 16-bit samples to 8-bit samples rather than making
- the driver to do it in the kernel.
-\layout Description
-
-SND_PCM_PINFO_16BITONLY If this bit is set, driver uses 16-bit format for
- 8-bit samples and does software conversion.
- This bit is set on broken SoundBlaster 16/AWE sound cards which can't do
- full 8-bit duplex.
- If this bit is set the application or higher digital audio layer should
- do conversion from 8-bit samples to 16-bit samples rather than making the
- driver to do it in the kernel.
-
-\layout Subsubsection*
-
-int snd_pcm_record_info(void *handle, snd_pcm_record_info_t *info)
-\layout Standard
-
-Fills the *info structure.
- Returns zero if successful, otherwise it returns an error code.
-
-\layout LyX-Code
-
-#define SND_PCM_RINFO_BATCH
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-0x00000001
-\layout LyX-Code
-
-#define SND_PCM_RINFO_8BITONLY
-\protected_separator
- 0x00000002
-\layout LyX-Code
-
-#define SND_PCM_RINFO_16BITONLY
-\protected_separator
-0x00000004
-\layout LyX-Code
-
-#define SND_PCM_RINFO_OVERRANGE
-\protected_separator
-0x00001000
-\layout Standard
-
-
-\protected_separator
-
-\layout LyX-Code
-
-struct snd_pcm_record_info {
-\layout LyX-Code
-
-
-\shape italic
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
- /* see SND_PCM_RINFO_XXXX */
-\layout LyX-Code
-
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
- unsigned int flags;
-\layout LyX-Code
-
-
-\shape italic
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
- /* supported formats */
-\layout LyX-Code
-
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
- unsigned int formats;
-\layout LyX-Code
-
-
-\shape italic
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
- /* min rate (in Hz) */
-\layout LyX-Code
-
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
- unsigned int min_rate;
-\layout LyX-Code
-
-
-\shape italic
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
- /* max rate (in Hz) */
-\layout LyX-Code
-
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
- unsigned int max_rate;
-\layout LyX-Code
-
-
-\shape italic
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
- /* min channels - voices (probably always 1) */
-\layout LyX-Code
-
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
- unsigned int min_channels;
-\layout LyX-Code
-
-
-\shape italic
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
- /* max channels - voices */
-\layout LyX-Code
-
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
- unsigned int max_channels;
-\layout LyX-Code
-
-
-\shape italic
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
- /* playback buffer size in bytes */
-\layout LyX-Code
-
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
- unsigned int buffer_size;
-\layout LyX-Code
-
-
-\shape italic
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
- /* min fragment size in bytes */
-\layout LyX-Code
-
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
- unsigned int min_fragment_size;
-\layout LyX-Code
-
-
-\shape italic
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
- /* max fragment size in bytes */
-\layout LyX-Code
-
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
- unsigned int max_fragment_size;
-\layout LyX-Code
-
-
-\shape italic
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
- /* align fragment value */
-\layout LyX-Code
-
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
- unsigned int fragment_align;
-\layout LyX-Code
-
-
-\shape italic
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
- /* supported formats directly by hardware */
-\layout LyX-Code
-
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
- unsigned int hw_formats;
-\layout LyX-Code
-
-
-\shape italic
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
- /* count of record switches */
-\layout LyX-Code
-
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
- unsigned int switches;
-\layout LyX-Code
-
-
-\shape italic
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
- /* reserved for future use */
-\layout LyX-Code
-
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
- unsigned char reserved[56];
-\layout LyX-Code
-
-};
-\layout Description
-
-SND_PCM_RINFO_BATCH Driver implements double buffering with this device.
- This means that the chip used for data processing has its own memory, and
- input will be more delayed than if a traditional codec chip is used.
-\layout Description
-
-SND_PCM_RINFO_8BITONLY If this bit is set, the driver uses 8-bit format
- for 16-bit samples and does software conversion.
- This bit is set on broken SoundBlaster 16/AWE sound cards which can't do
- full 16-bit duplex.
- If this bit is set application or higher digital audio layer should do
- the conversion from 16-bit samples to 8-bit samples rather than making
- the driver to do it in the kernel.
-\layout Description
-
-SND_PCM_RINFO_16BITONLY If this bit is set, driver uses 16-bit format for
- 8-bit samples and does software conversion.
- This bit is set on broken SoundBlaster 16/AWE sound cards which can't do
- full 8-bit duplex.
- If this bit is set the application or higher digital audio layer should
- do conversion from 8-bit samples to 16-bit samples rather than making the
- driver to do it in the kernel.
-
-\layout Description
-
-SND_PCM_RINFO_OVERRANGE If this bit is set\i \c{ }
- the hardware can do ADC over-range
- detection.
-\layout Subsubsection*
-
-int snd_pcm_playback_switches(void *handle)
-\layout Standard
-
-Returns count of PCM playback switches.
- In this contents switch means universal control interface between kernel
- and application which allows variable type control.
- Function returns count if successful, otherwise it returns an error code.
- Return value should be zero if sound card doesn't have any PCM playback
- switch.
-\layout Subsubsection*
-
-int snd_pcm_playback_switch(void *handle, const char *switch_id)
-\layout Standard
-
-Returns index for switch with name
-\shape italic
-switch_id
-\shape default
-.
- Function returns switch index if successful, otherwise it returns an error
- code.
-\layout Subsubsection*
-
-int snd_pcm_playback_switch_read(void *handle\i \c{ }
- int switchn\i \c{ }
- snd_pcm_switch_t
- *data)
-\layout Standard
-
-Fills the
-\shape italic
-*data
-\shape default
- structure with data about switch with index
-\shape italic
-switchn
-\shape default
-.
- Function returns zero if successful, otherwise it returns an error code.
-
-\layout LyX-Code
-
-
-\shape italic
-/* 0 or 1 (enable member of union) */
-\layout LyX-Code
-
-#define SND_PCM_SW_TYPE_BOOLEAN
-\protected_separator
-
-\protected_separator
-
-\protected_separator
- 0
-\layout LyX-Code
-
-
-\shape italic
-/* 0 to 255 - from low to high (data8[0] member of union) */
-\layout LyX-Code
-
-#define SND_PCM_SW_TYPE_BYTE
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-1
-\layout LyX-Code
-
-
-\shape italic
-/* 0 to 65535 - from low to high (data16[0] member of union) */
-\layout LyX-Code
-
-#define SND_PCM_SW_TYPE_WORD
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-2
-\layout LyX-Code
-
-
-\shape italic
-/* 0 to 4294967296 \i \={ }
- from low to high (data32[0] member of union) */
-\layout LyX-Code
-
-#define SND_PCM_SW_TYPE_DWORD
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
- 3
-\layout LyX-Code
-
-
-\shape italic
-/* user type - no type control */
-\layout LyX-Code
-
-#define SND_PCM_SW_TYPE_USER
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-(~0)
-\layout Standard
-
-
-\protected_separator
-
-\layout LyX-Code
-
-struct snd_pcm_switch {
-\layout LyX-Code
-
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\shape italic
-/* switch index (filled by application) */
-\layout LyX-Code
-
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
- unsigned int switchn;
-\layout LyX-Code
-
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\shape italic
-/* identification of switch (for driver) */
-\layout LyX-Code
-
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
- unsigned char name[32];
-\layout LyX-Code
-
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\shape italic
-/* type of switch value \i \={ }
- See SND_PCM_SW_TYPE_XXXX */
-\layout LyX-Code
-
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
- unsigned int type;
-\layout LyX-Code
-
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\shape italic
-/* low range value */
-\layout LyX-Code
-
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
- unsigned int low;
-\layout LyX-Code
-
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\shape italic
-/* high range value */
-\layout LyX-Code
-
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
- unsigned int high;
-\layout LyX-Code
-
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
- union {
-\layout LyX-Code
-
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
- unsigned int enable;
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\shape italic
-/* 0 = off\i \c{ }
- 1 = on */
-\layout LyX-Code
-
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
- unsigned char data8[32];
-\protected_separator
-
-\protected_separator
-
-\shape italic
-/* 8-bit data */
-\layout LyX-Code
-
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
- unsigned short data16[16];
-\protected_separator
-
-\shape italic
-/* 16-bit data */
-\layout LyX-Code
-
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
- unsigned int data32[8];
-\protected_separator
-
-\protected_separator
-
-\shape italic
-/* 32-bit data */
-\layout LyX-Code
-
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
- } value;
-\layout LyX-Code
-
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\shape italic
-/* reserved for future use \i \={ }
- must be zero !!! */
-\layout LyX-Code
-
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
- unsigned char reserved[32];
-\layout LyX-Code
-
-}
-\layout Subsubsection*
-
-int snd_pcm_playback_switch_write(void *handle\i \c{ }
- int switchn\i \c{ }
- snd_pcm_switch_t
- *data)
-\layout Standard
-
-Writes the
-\shape italic
-*data
-\shape default
- structure with data about switch with index
-\shape italic
-switchn
-\shape default
- to kernel.
- Function returns zero if successful, otherwise it returns an error code.
-
-\layout Subsubsection*
-
-int snd_pcm_record_switches(void *handle)
-\layout Standard
-
-Returns count of PCM record switches.
- In this context 'switch' means universal control interface between kernel
- and application which allows various types of control.
- Function returns count if successful, otherwise it returns an error code.
- Return value should be zero if sound card doesn't have any PCM record switch.
-\layout Subsubsection*
-
-int snd_pcm_record_switch(void *handle, const char *switch_id)
-\layout Standard
-
-Returns index for switch with name
-\shape italic
-switch_id
-\shape default
-.
- Function returns switch index if successful, otherwise it returns an error
- code.
-\layout Subsubsection*
-
-int snd_pcm_record_switch_read(void *handle\i \c{ }
- int switchn\i \c{ }
- snd_pcm_switch_t
- *data)
-\layout Standard
-
-Fills the
-\shape italic
-*data
-\shape default
- structure with data about switch with index
-\shape italic
-switchn
-\shape default
-.
- Function returns zero if successful, otherwise it returns an error code.
-\layout Subsubsection*
-
-int snd_pcm_record_switch_write(void *handle\i \c{ }
- int switchn\i \c{ }
- snd_pcm_switch_t
- *data)
-\layout Standard
-
-Writes the
-\shape italic
-*data
-\shape default
- structure with data about switch with index
-\shape italic
-switchn
-\shape default
- to kernel.
- Function returns zero if successful, otherwise it returns an error code.
-
-\layout Subsubsection*
-
-int snd_pcm_playback_format(void *handle, snd_pcm_format_t *format)
-\layout Standard
-
-Sets up format, rate (in Hz) and number of channels for playback, in the
- desired direction.
- Function returns zero if successful, otherwise it returns an error code.
-\layout LyX-Code
-
-struct snd_pcm_format {
-\layout LyX-Code
-
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
- unsigned int format;
-\protected_separator
-
-\protected_separator
-
-\shape italic
-/* SND_PCM_SFMT_XXXX */
-\layout LyX-Code
-
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
- unsigned int rate;
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\shape italic
-/* rate in Hz */
-\layout LyX-Code
-
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
- unsigned int channels;
-\protected_separator
-
-\shape italic
-/* channels (voices) */
-\layout LyX-Code
-
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
- unsigned char reserved[16];
-\layout LyX-Code
-
-};
-\layout Subsubsection*
-
-int snd_pcm_record_format(void *handle, snd_pcm_format_t *format)
-\layout Standard
-
-Sets up format, rate (in Hz) and number of channels for used for recording
- in the specified direction.
- Function returns zero if successful, otherwise it returns an error code.
-
-\layout LyX-Code
-
-struct snd_pcm_format {
-\layout LyX-Code
-
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
- unsigned int format;
-\protected_separator
-
-\protected_separator
-
-\shape italic
-/* SND_PCM_SFMT_XXXX */
-\layout LyX-Code
-
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
- unsigned int rate;
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\shape italic
-/* rate in Hz */
-\layout LyX-Code
-
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
- unsigned int channels;
-\protected_separator
-
-\shape italic
-/* channels (voices) */
-\layout LyX-Code
-
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
- unsigned char reserved[16];
-\layout LyX-Code
-
-};
-\layout Subsubsection*
-
-int snd_pcm_playback_params(void *handle, snd_pcm_playback_params_t *params)
-\layout Standard
-
-Sets various parameters for playback direction.
- Function returns zero if successful, otherwise it returns an error code.
-
-\layout LyX-Code
-
-struct snd_pcm_playback_params {
-\layout LyX-Code
-
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
- int fragment_size;
-\layout LyX-Code
-
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
- int fragments_max;
-\layout LyX-Code
-
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
- int fragments_room;
-\layout LyX-Code
-
-
-\shape italic
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
- /* reserved for future use - must be filled with zero */
-\layout LyX-Code
-
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
- unsigned char reserved[16];
-\layout LyX-Code
-
-};
-\layout Description
-
-fragment_size Requested size of fragment.
- This value should be aligned for current format (for example to 4 if stereo
- 16-bit samples are used) or with the
-\shape italic
-fragment_align
-\shape default
- variable from
-\shape italic
-snd_pcm_playback_info_t
-\shape default
- structure.
- Its range can be from
-\shape italic
-min_fragment_size
-\shape default
- to
-\shape italic
-max_fragment_size
-\shape default
-.
-\layout Description
-
-fragments_max Maximum number of fragments in queue for wakeup.
- This number doesn't include partly used fragments.
- If the current count of filled playback fragments is greater than this
- value the driver will block the application or return immediately back
- if non-block mode is active.
-\layout Description
-
-fragments_room Minimum number of fragments writable for wakeup.
- This value should in most cases be 1 which means return back to application
- if at least one fragment is free for playback.
- This value includes partly used fragments, too.
-\layout Subsubsection*
-
-int snd_pcm_record_params(void *handle, snd_pcm_record_params_t *params)
-\layout Standard
-
-Function sets various parameters for the recording direction.
- Function returns zero if successful, otherwise it returns an error code.
-\layout LyX-Code
-
-struct snd_pcm_record_params {
-\layout LyX-Code
-
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
- int fragment_size;
-\layout LyX-Code
-
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
- int fragments_min;
-\layout LyX-Code
-
-
-\shape italic
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
- /* reserved for future use - must be filled with zero */
-\layout LyX-Code
-
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
- unsigned char reserved[16];
-\layout LyX-Code
-
-};
-\layout Description
-
-fragment_size Requested size of fragment.
- This value should be aligned for current format (for example to 4 if stereo
- 16-bit samples are used) or set to the
-\shape italic
-fragment_align
-\shape default
- variable from
-\shape italic
-snd_pcm_playback_info_t
-\shape default
- structure.
- Its range can be from
-\shape italic
-min_fragment_size
-\shape default
- to
-\shape italic
-max_fragment_size
-\shape default
-.
-\layout Description
-
-fragments_min Minimum filled fragments for wakeup.
- Driver blocks the application (if block mode is selected) until input buffer
- is filled with less than the number of fragments specified with this value.
-\layout Subsubsection*
-
-int snd_pcm_playback_status(void *handle, snd_pcm_playback_status_t *status)
-\layout Standard
-
-Fills the
-\shape italic
-*status
-\shape default
- structure.
- Function returns zero if successful, otherwise it returns an error code.
-\layout LyX-Code
-
-struct snd_pcm_playback_status {
-\layout LyX-Code
-
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
- unsigned int rate;
-\layout LyX-Code
-
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
- int fragments;
-\layout LyX-Code
-
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
- int fragment_size;
-\layout LyX-Code
-
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
- int count;
-\layout LyX-Code
-
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
- int queue;
-\layout LyX-Code
-
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
- int underrun;
-\layout LyX-Code
-
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
- struct timeval time;
-\layout LyX-Code
-
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
- struct timeval stime;
-\layout LyX-Code
-
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
- int scount;
-\layout LyX-Code
-
-
-\shape italic
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
- /* reserved for future use - must be filled with zero */
-\layout LyX-Code
-
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
- unsigned char reserved[16];
-\layout LyX-Code
-
-};
-\layout Description
-
-rate Real playback rate.
- This value reflects hardware limitations.
-
-\layout Description
-
-fragments Currently allocated fragments by the driver for playback direction.
-\layout Description
-
-fragment_size Current fragment size used by driver for the playback direction.
-\layout Description
-
-count Count of bytes writable without blocking.
-\layout Description
-
-queue Count of bytes in queue.
- Note:
-\shape italic
-(fragments*fragment_size) - queue
-\shape default
- should not be equal to
-\shape italic
-count
-\shape default
-.
-\layout Description
-
-underrun This value tells the application the number of underruns since
- the last call to
-\shape italic
-snd_pcm_playback_status
-\shape default
-\emph on
-()
-\emph default
-.
-
-\layout Description
-
-time Estimated time when the next written sample will actually be played
- (time is always in the future).
- The estimate is calculated with: current time + sample queue
-\emph on
-
-\emph default
-converted to time (number of samples waiting for write to device, i.e., the
- same as the
-\emph on
-queue
-\emph default
-member above).
- This value should be used for time synchronization.
- Returned value is in the same format as returned from the standard C function
-
-\emph on
-gettimeofday
-\emph default
-(&
-\emph on
-time
-\emph default
-,
-\emph on
-NULL
-\emph default
-).
- This variable contains valid information only if playback time mode is
- enabled (see
-\shape italic
-snd_pcm_playback_time()
-\shape default
- function).
-
-\layout Description
-
-stime Time when playback was started.
- This variable contains valid information only if playback time mode is
- enabled (see
-\shape italic
-snd_pcm_playback_time()
-\shape default
- function).
-\layout Description
-
-scount Number of bytes processed (actually played) from playback start.
- This number is not necessarily the same as byte count written by application.
-\layout Standard
-\added_space_top 0.3cm \added_space_bottom 0.3cm \align center
-
-\begin_inset Figure size 654 212
-file pcmbuf.ps
-width 3 100
-flags 9
-
-\end_inset
-
-
-\layout Standard
-
-The figure above shows an example situation in the audio playback buffer
- in the ALSA driver.
- The driver splits the audio buffer into 16
-\emph on
-fragments
-\emph default
-, each being
-\emph on
- fragment_size
-\emph default
-bytes long.
- Fragments 0 and 12-15 are filled with samples.
- Fragment 1 is filled partly (about 75%).
- Driver is playing and current playback position is in fragment 12 (about
- 35%).
- As you can see\i \c{ }
- free space (structure member
-\shape italic
-count
-\shape default
-) is counted without including the fragment which is being played.
-\layout Subsubsection*
-
-int snd_pcm_record_status(void *handle, snd_pcm_record_status_t *status)
-\layout Standard
-
-Fills the
-\shape italic
-*status
-\shape default
- structure.
- Function returns zero if successful, otherwise it returns an error code.
-\layout LyX-Code
-
-struct snd_pcm_record_status {
-\layout LyX-Code
-
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
- unsigned int rate;
-\layout LyX-Code
-
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
- int fragments;
-\layout LyX-Code
-
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
- int fragment_size;
-\layout LyX-Code
-
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
- int count;
-\layout LyX-Code
-
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
- int free;
-\layout LyX-Code
-
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
- int overrun;
-\layout LyX-Code
-
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
- struct timeval time;
-\layout LyX-Code
-
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
- struct timeval stime;
-\layout LyX-Code
-
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
- int scount;
-\layout LyX-Code
-
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
- int overrange;
-\layout LyX-Code
-
-
-\shape italic
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
- /* reserved for future use - must be filled with zero */
-\layout LyX-Code
-
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
- unsigned char reserved[16];
-\layout LyX-Code
-
-};
-\layout Description
-
-rate Real record rate.
- This value reflects hardware limitations.
-\layout Description
-
-fragments Currently allocated fragments by driver for the record direction.
-\layout Description
-
-fragment_size Current fragment size used by driver for the record direction.
-\layout Description
-
-count Count of bytes readable without blocking.
-\layout Description
-
-free Count of bytes in buffer still free.
- Note:
-\shape italic
-(fragments*fragment_size) - free
-\shape default
- should not be equal to
-\shape italic
-count
-\shape default
-.
-\layout Description
-
-overrun This value tells application the count of overruns since the last
- call to
-\shape italic
-snd_pcm_record_status
-\shape default
-.
-\layout Description
-
-time Returns a timestamp for the next sample to be read from the record
- ring buffer (time is always in the past).
- The timestamp is calculated with: current time - sample queue converted
- to time (waiting for application read() + current position in fragment
- is the same as record count + current position in fragment).
- This value should be used for time synchronization.
- Returned value is in the same format as returned by the standard C function
- gettimeofday(&time, NULL).
- This variable contains right valid information only if record time mode
- is enabled (see
-\shape italic
-snd_pcm_record_time()
-\shape default
- function).
-
-\layout Description
-
-stime Time when record was started.
- This variable contains valid information only if record time mode is enabled
- (see
-\shape italic
-snd_pcm_record_time
-\shape default
- function).
-\layout Description
-
-scount Number of bytes processed (actually recorded) from record start (stime).
- This number is not necessarily the same as the byte count read by application.
-\layout Description
-
-overrange ADC overrange count.
- This value is used only when
-\shape italic
-SND_PCM_RINFO_OVERRANGE
-\shape default
- bit in
-\shape italic
-struct snd_pcm_record_info_t->flags
-\shape default
- is set (if hardware supports this feature).
-\layout Standard
-\added_space_top 0.3cm \added_space_bottom 0.3cm \align center
-
-\begin_inset Figure size 595 121
-file pcmbuf1.ps
-width 3 100
-flags 9
-
-\end_inset
-
-
-\layout Standard
-
-The figure above shows an example situation in the audio record buffer in
- the ALSA driver.
- The driver splits the audio buffer into 16
-\emph on
-fragments
-\emph default
-, each being
-\emph on
-fragment_size
-\emph default
-bytes in length.
- Fragments 0 and 12-15 are filled with samples.
- Fragment 1 is partly filled (about 75%) and at the end of the filled area
- is the active record position.
- Data which is ready for the application begins in fragment 12 (about 35%).
- As you can see\i \c{ }
- free space (structure member
-\shape italic
-free
-\shape default
-) is counted without including the fragment which is partly filled with
- samples and the application reads data from this fragment.
-\layout Subsubsection*
-
-int snd_pcm_drain_playback(void *handle)
-\layout Standard
-
-This function stops and drains (destroys) the playback buffers immediately.
- Function returns zero if successful, otherwise it returns an error code.
-
-\layout Subsubsection*
-
-int snd_pcm_flush_playback(void *handle)
-\layout Standard
-
-This function flushes the playback buffers.
- It blocks the program while the all the waiting samples in kernel playback
- buffers are processed.
- Function returns zero if successful, otherwise it returns an error code.
-\layout Subsubsection*
-
-int snd_pcm_flush_record(void *handle)
-\layout Standard
-
-This function flushes (destroys) record buffers.
- Function returns zero if successful, otherwise it returns an error code.
-
-\layout Subsubsection*
-
-int snd_pcm_playback_pause(void *handle\i \c{ }
- int enable)
-\layout Standard
-
-This function pauses playback if
-\shape italic
-enable
-\shape default
- is non-zero.
- To restore playing mode call this function with
-\shape italic
-enable
-\shape default
- equal to zero.
- Function returns zero if successful, otherwise it returns an error code.
-
-\layout Subsubsection*
-
-int snd_pcm_playback_time(void *handle, int enable)
-\layout Standard
-
-This function enables or disables time mode for the playback direction.
- Time mode is useful in synchronizing an application with other events.
- Function returns zero if successful, otherwise it returns an error code.
-\layout Subsubsection*
-
-int snd_pcm_record_time(void *handle, int enable)
-\layout Standard
-
-This function enables or disables time mode for record direction.
- Time mode is useful in synchronizing an application with other events.
- Function returns zero if successful, otherwise it returns an error code.
-\layout Subsubsection*
-
-ssize_t snd_pcm_write(void *handle, const void *buffer, size_t size)
-\layout Standard
-
-Writes samples to the device which must be in the proper format specified
- by the
-\shape italic
-snd_pcm_playback_format
-\shape default
- function.
- Function returns zero or positive value if playback was successful (value
- represents count of bytes which were successfully written to device) or
- an error value if an error occurred.
- Function will suspend process if block mode is active.
-\layout Subsubsection*
-
-ssize_t snd_pcm_read(void *handle, void *buffer, size_t size)
-\layout Standard
-
-Function reads samples from driver.
- Samples are in format specified by
-\shape italic
-snd_pcm_record_format
-\shape default
- function.
- Function returns zero or positive value if record was success (value represents
- count of bytes which was successfully read from device) or negative error
- value if error occurred.
- Function will suspend process if block mode is active.
-\layout Subsubsection
-
-Example
-\layout Standard
-
-The following example shows how to play the first 512kB from the /tmp/test.au
- file with sound card #0 and PCM device #0:
-\layout LyX-Code
-
-int card = 0, device = 0, err, fd, count, size, idx;
-\layout LyX-Code
-
-void *handle;
-\layout LyX-Code
-
-snd_pcm_format_t format;
-\layout LyX-Code
-
-char *buffer;
-\layout Standard
-
-
-\protected_separator
-
-\layout LyX-Code
-
-buffer = (char *)malloc(512 * 1024);
-\layout LyX-Code
-
-if (!buffer) return;
-\layout LyX-Code
-
-if ((err = snd_pcm_open(&handle, card, device,
-\layout LyX-Code
-
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
- SND_PCM_OPEN_PLAYBACK)) < 0) {
-\layout LyX-Code
-
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
- fprintf(stderr, "open failed: %s
-\backslash
-n", snd_strerror( err ));
-\layout LyX-Code
-
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
- return;
-\layout LyX-Code
-
-}
-\layout LyX-Code
-
-bzero(&format\i \c{ }
- sizeof(format));
-\layout LyX-Code
-
-format.format = SND_PCM_SFMT_MU_LAW;
-\layout LyX-Code
-
-format.rate = 8000;
-\layout LyX-Code
-
-format.channels = 1;
-\layout LyX-Code
-
-if ((err = snd_pcm_playback_format(handle, &format)) < 0) {
-\layout LyX-Code
-
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
- fprintf(stderr, "format setup failed: %s
-\backslash
-n",
-\layout LyX-Code
-
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-snd_strerror( err ));
-\layout LyX-Code
-
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
- snd_pcm_close( handle );
-\layout LyX-Code
-
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
- return;
-\layout LyX-Code
-
-}
-\layout LyX-Code
-
-fd = open("/tmp/test.au", O_RDONLY);
-\layout LyX-Code
-
-if (fd < 0) {
-\layout LyX-Code
-
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
- perror("open file");
-\layout LyX-Code
-
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
- snd_pcm_close(handle);
-\layout LyX-Code
-
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
- return;
-\layout LyX-Code
-
-}
-\layout LyX-Code
-
-idx = 0;
-\layout LyX-Code
-
-count = read(fd, buffer, 512 * 1024);
-\layout LyX-Code
-
-if (count <= 0) {
-\layout LyX-Code
-
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
- perror("read from file");
-\layout LyX-Code
-
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
- snd_pcm_close( handle );
-\layout LyX-Code
-
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
- return;
-\layout LyX-Code
-
-}
-\layout LyX-Code
-
-close( fd );
-\layout LyX-Code
-
-if (!memcmp(buffer, ".snd", 4)) {
-\layout LyX-Code
-
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
- idx = (buffer[4]<<24)|(buffer[5]<<16)|
-\layout LyX-Code
-
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
- (buffer[6]<<8)|(buffer[7]);
-\layout LyX-Code
-
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
- if (idx > 128) idx = 128;
-\layout LyX-Code
-
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
- if (idx > count) idx = count;
-\layout LyX-Code
-
-}
-\layout LyX-Code
-
-size = snd_pcm_write(handle, &buffer[ idx ], count - idx);
-\layout LyX-Code
-
-printf("Bytes written %i from %i...
-\backslash
-n", size, count - idx);
-\layout LyX-Code
-
-snd_pcm_close(handle);
-\layout LyX-Code
-
-free(buffer);
-\layout Subsection
-
-PCM Loopback Interface
-\layout Standard
-
-This interface is designed to pass data currently being played or recorded
- from one application to another application for other processing like a
- graphical equalizer\i \c{ }
- sample recorder etc...
- The programmer should be aware that each loopback connection eats CPU time
- (for data copying from the process which is doing the playback or record).
-\layout Subsubsection*
-
-int snd_pcm_loopback_open(void **handle, int card, int device, int mode)
-\layout Standard
-
-Creates a new handle and opens a connection to the kernel sound audio loopback
- interface for sound card number
-\shape italic
-card
-\shape default
- (0-N) and audio device number
-\shape italic
-device
-\shape default
-.
- Function also checks if protocol is compatible to prevent use of old programs
- with a new kernel API.
- Function returns zero if successful otherwise it returns an error code.
- Error code -EBUSY is returned when another process owns the selected direction.
-\layout Standard
-
-The following modes should be used for the
-\shape italic
-mode
-\shape default
- argument:
-\layout LyX-Code
-
-#define SND_PCM_LB_OPEN_PLAYBACK
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-0
-\layout LyX-Code
-
-#define SND_PCM_LB_OPEN_RECORD
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-1
-\layout Subsubsection*
-
-int snd_pcm_loopback_close(void *handle)
-\layout Standard
-
-Frees all resources allocated with audio handle and closes the connection
- to the kernel sound audio interface.
- Function returns zero if successful, otherwise it returns an error code.
-\layout Subsubsection*
-
-int snd_pcm_loopback_file_descriptor(void *handle)
-\layout Standard
-
-Returns the file descriptor of the connection to the kernel sound audio
- interface.
- Function returns an error code if an error was encountered.
-\layout Standard
-
-The file descriptor should be used for the
-\shape italic
-select(2)
-\shape default
- synchronous multiplexer function for setting the read direction.
- Application should call
-\shape italic
-snd_pcm_loopback_read()
-\shape default
- function if data is waiting to be read.
-\layout Subsubsection*
-
-int snd_pcm_loopback_block_mode(void *handle, int enable)
-\layout Standard
-
-Sets up block (default) or non-block mode for a handle.
- Block mode suspends execution of a program when
-\shape italic
-snd_pcm_loopback_read()
-\shape default
- is called for the time until some data arrives for file descriptor.
- In non-block mode, programs aren't suspended and the above function returns
- immediately with the count of bytes which were read by the driver.
- When used in this way, don't try to use the entire buffer after the call,
- but instead process the number of bytes returned, and call the function
- again.
-\layout Subsubsection*
-
-int snd_pcm_loopback_stream_mode(void *handle, int mode)
-\layout Standard
-
-Sets up stream mode which should be one of these values:
-\layout LyX-Code
-
-#define SND_PCM_LB_STREAM_MODE_RAW
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-0
-\layout LyX-Code
-
-#define SND_PCM_LB_STREAM_MODE_PACKET
-\protected_separator
-1
-\layout Standard
-
-Mode raw (default mode) means that the stream contains only PCM samples.
- Packet mode is more complicated.
- The stream contains a header at the begining of the packet.
- Information like data type and data size is contain in this header.
-\layout LyX-Code
-
-#define SND_PCM_LB_TYPE_DATA
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-0
-\protected_separator
-
-\shape italic
-/* sample data */
-\layout LyX-Code
-
-#define SND_PCM_LB_TYPE_FORMAT
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
- 1
-\protected_separator
-
-\shape italic
-/* PCM format */
-\layout Standard
-
-
-\protected_separator
-
-\layout LyX-Code
-
-struct snd_pcm_loopback_header {
-\layout LyX-Code
-
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
- unsigned int size;
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\shape italic
-/* block size */
-\layout LyX-Code
-
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
- unsigned int type;
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\shape italic
-/* block type (SND_PCM_LB_TYPE_*) */
-\layout LyX-Code
-
-};
-\layout Subsubsection*
-
-int snd_pcm_loopback_format(void *handle, snd_pcm_format_t *format)
-\layout Standard
-
-Get current format for PCM stream.
-
-\layout LyX-Code
-
-struct snd_pcm_format {
-\layout LyX-Code
-
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
- unsigned int format;
-\protected_separator
-
-\protected_separator
-
-\shape italic
-/* SND_PCM_SFMT_XXXX */
-\layout LyX-Code
-
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
- unsigned int rate;
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\shape italic
-/* rate in Hz */
-\layout LyX-Code
-
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
- unsigned int channels;
-\protected_separator
-
-\shape italic
-/* number of channels (voices) */
-\layout LyX-Code
-
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
- unsigned char reserved[16];
-\layout LyX-Code
-
-};
-\layout Subsubsection*
-
-ssize_t snd_pcm_loopback_read(void *handle, void *buffer, size_t size)
-\layout Standard
-
-This function reads samples or loopback packets from the stream.
- Data depends on stream mode which should be set with
-\shape italic
-snd_pcm_loopback_stream_mode()
-\shape default
- function.
- Function returns zero or positive value if record was success (value represents
- count of bytes which were successfully read from device) or negative error
- value if error occurred.
- Function will suspend process if block mode is active.
-\layout Section
-
-RawMidi Interface
-\layout Standard
-
-RawMidi Interface is designed to write or read raw (unchanged) MIDI data
- over the MIDI line.
- MIDI stands Musical Instrument Digital Interface and more informations
- about this standard can be found at
-\series bold
-http://www.midi.org
-\series default
-.
-\layout Subsection
-
-Low Level Layer
-\layout Standard
-
-RawMidi devices are opened exclusively for a selected direction.
- While more than one process may not open a given MIDI device in the same
- direction simultaniously, seperate processes may open a single MIDI device
- in different directions (i.e.
- process one opens a MIDI device in playback direction and process two opens
- the same device in record direction).
- Audio devices (with MIDI ports) return EBUSY error to applications when
- other applications have already opened the requested direction.
-\layout Subsubsection*
-
-int snd_rawmidi_open(void **handle, int card, int device, int mode)
-\layout Standard
-
-Creates a new handle and opens a connection to the kernel sound audio interface
- for sound card number
-\shape italic
-card
-\shape default
- (0-N) and rawmidi device number
-\shape italic
-device
-\shape default
-.
- Function also checks if protocol is compatible to prevent use of old programs
- with a new kernel API.
- Function returns zero if successful, otherwise it returns an error code.
- Error code -EBUSY is returned when another process owns the selected direction.
-\layout Standard
-
-The following modes should be used for the
-\shape italic
-mode
-\shape default
- argument:
-\layout LyX-Code
-
-#define SND_RAWMIDI_OPEN_OUTPUT
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-(O_WRONLY)
-\layout LyX-Code
-
-#define SND_RAWMIDI_OPEN_INPUT
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-(O_RDONLY)
-\layout LyX-Code
-
-#define SND_RAWMIDI_OPEN_DUPLEX
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-(O_RDWR)
-\layout Subsubsection*
-
-int snd_rawmidi_close(void *handle)
-\layout Standard
-
-Frees all resources allocated with audio handle and closes the connection
- to the kernel sound rawmidi interface.
- Function returns zero if successful, otherwise it returns an error code.
-\layout Subsubsection*
-
-int snd_rawmidi_file_descriptor(void *handle)
-\layout Standard
-
-Returns the file descriptor of the connection to the kernel sound audio
- interface.
- Function returns an error code if an error was encountered.
-\layout Standard
-
-The file descriptor should be used for the
-\shape italic
-select(2)
-\shape default
- synchronous multiplexer function for setting the read direction.
- Application should call
-\shape italic
-snd_rawmidi_read()
-\shape default
- or
-\shape italic
-snd_rawmidi_write()
-\shape default
- functions if data is waiting to be read or a write can be performed.
- Calling these functions is highly recommended.
-\layout Subsubsection*
-
-int snd_rawmidi_block_mode(void *handle, int enable)
-\layout Standard
-
-Sets up block (default) or non-block mode for a handle.
- Block mode suspends execution of a program when
-\shape italic
-snd_rawmidi_read()
-\shape default
- or
-\shape italic
-snd_rawmidi_write()
-\shape default
- is called for the time which is needed for the actual output or input over
- of the selected limit.
- In non-block mode, programs aren't suspended and the above functions return
- immediately with the count of bytes which were read or written by the driver.
- When used in this way, don't try to use the entire buffer after the call,
- but instead process the number of bytes returned, and call the function
- again.
-\layout Subsubsection*
-
-int snd_rawmidi_info(void *handle, snd_pcm_info_t *info)
-\layout Standard
-
-Fills the
-\shape italic
-*info
-\shape default
- structure with data about the PCM device selected by
-\shape italic
-*handle
-\shape default
-.
- Function returns zero if successful, otherwise it returns an error code.
-\layout LyX-Code
-
-
-\shape italic
-/*
-\shape default
- device is capable rawmidi output *
-\shape italic
-/
-\layout LyX-Code
-
-#define SND_RAWMIDI_INFO_OUTPUT
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-0x00000001
-\layout LyX-Code
-
-
-\shape italic
-/* device is capable rawmidi input */
-\layout LyX-Code
-
-#define SND_RAWMIDI_INFO_INPUT
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
- 0x00000002
-\layout LyX-Code
-
-
-\shape italic
-/* device is capable duplex mode */
-\layout LyX-Code
-
-#define SND_RAWMIDI_INFO_DUPLEX
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-0x00000004
-\layout Standard
-
-
-\protected_separator
-
-\layout LyX-Code
-
-struct snd_rawmidi_info {
-\layout LyX-Code
-
-
-\shape italic
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
- /* sound card type */
-\layout LyX-Code
-
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
- unsigned int type;
-\layout LyX-Code
-
-
-\shape italic
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
- /* see SND_RAWMIDI_INFO_XXXX */
-\layout LyX-Code
-
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
- unsigned int flags;
-\layout LyX-Code
-
-
-\shape italic
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
- /* ID of this PCM device */
-\layout LyX-Code
-
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
- unsigned char id[32];
-\layout LyX-Code
-
-
-\shape italic
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
- /* name of this device */
-\layout LyX-Code
-
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
- unsigned char name[80];
-\layout LyX-Code
-
-
-\shape italic
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
- /* reserved for future use */
-\layout LyX-Code
-
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
- unsigned char reserved[64];
-\layout LyX-Code
-
-};
-\layout Subsubsection*
-
-int snd_rawmidi_output_info(void *handle, snd_rawmidi_output_info_t *info)
-\layout Standard
-
-Fills the *info structure with data about rawmidi output.
- Function returns zero if successful, otherwise it returns an error code.
-\layout LyX-Code
-
-struct snd_rawmidi_output_info {
-\layout LyX-Code
-
-
-\shape italic
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
- /* count of output switches */
-\layout LyX-Code
-
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
- unsigned int switches;
-\layout LyX-Code
-
-
-\shape italic
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
- /* reserved for future use */
-\layout LyX-Code
-
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
- unsigned char reserved[64];
-\layout LyX-Code
-
-};
-\layout Subsubsection*
-
-int snd_rawmidi_input_info(void *handle, snd_pcm_record_info_t *info)
-\layout Standard
-
-Fills the *info structure.
- Returns zero if successful, otherwise it returns an error code.
-
-\layout LyX-Code
-
-struct snd_rawmidi_input_info {
-\layout LyX-Code
-
-
-\shape italic
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
- /* count of output switches */
-\layout LyX-Code
-
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
- unsigned int switches;
-\layout LyX-Code
-
-
-\shape italic
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
- /* reserved for future use */
-\layout LyX-Code
-
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
- unsigned char reserved[64];
-\layout LyX-Code
-
-};
-\layout Subsubsection*
-
-int snd_rawmidi_output_switches(void *handle)
-\layout Standard
-
-Returns count of rawmidi output switches.
- In this context 'switch' means universal control interface between kernel
- and application which allows various types of control.
- Function returns count if successful, otherwise it returns an error code.
- Return value should be zero if sound card doesn't have any rawmidi output
- switch.
-\layout Subsubsection*
-
-int snd_rawmidi_output_switch(void *handle, const char *switch_id)
-\layout Standard
-
-Returns index for switch with name
-\shape italic
-switch_id
-\shape default
-.
- Function returns switch index if successful, otherwise it returns an error
- code.
-\layout Subsubsection*
-
-int snd_rawmidi_output_switch_read(void *handle\i \c{ }
- int switchn\i \c{ }
- snd_rawmidi_switch_t
- *data)
-\layout Standard
-
-Fills the
-\shape italic
-*data
-\shape default
- structure with data about switch with index
-\shape italic
-switchn
-\shape default
-.
- Function returns zero if successful, otherwise it returns an error code.
-
-\layout LyX-Code
-
-
-\shape italic
-/* 0 or 1 (enable member of union) */
-\layout LyX-Code
-
-#define SND_PCM_SW_TYPE_BOOLEAN
-\protected_separator
-
-\protected_separator
-
-\protected_separator
- 0
-\layout LyX-Code
-
-
-\shape italic
-/* 0 to 255 - from low to high (data8[0] member of union) */
-\layout LyX-Code
-
-#define SND_PCM_SW_TYPE_BYTE
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-1
-\layout LyX-Code
-
-
-\shape italic
-/* 0 to 65535 - from low to high (data16[0] member of union) */
-\layout LyX-Code
-
-#define SND_PCM_SW_TYPE_WORD
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-2
-\layout LyX-Code
-
-
-\shape italic
-/* 0 to 4294967296 \i \={ }
- from low to high (data32[0] member of union) */
-\layout LyX-Code
-
-#define SND_PCM_SW_TYPE_DWORD
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
- 3
-\layout LyX-Code
-
-
-\shape italic
-/* user type - no type control */
-\layout LyX-Code
-
-#define SND_PCM_SW_TYPE_USER
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-(~0)
-\layout Standard
-
-
-\protected_separator
-
-\layout LyX-Code
-
-struct snd_rawmidi_switch {
-\layout LyX-Code
-
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\shape italic
-/* switch index (filled by application) */
-\layout LyX-Code
-
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
- unsigned int switchn;
-\layout LyX-Code
-
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\shape italic
-/* identification of switch (for driver) */
-\layout LyX-Code
-
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
- unsigned char name[32];
-\layout LyX-Code
-
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\shape italic
-/* type of switch value \i \={ }
- See SND_PCM_SW_TYPE_XXXX */
-\layout LyX-Code
-
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
- unsigned int type;
-\layout LyX-Code
-
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\shape italic
-/* low range value */
-\layout LyX-Code
-
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
- unsigned int low;
-\layout LyX-Code
-
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\shape italic
-/* high range value */
-\layout LyX-Code
-
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
- unsigned int high;
-\layout LyX-Code
-
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
- union {
-\layout LyX-Code
-
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
- unsigned int enable;
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\shape italic
-/* 0 = off\i \c{ }
- 1 = on */
-\layout LyX-Code
-
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
- unsigned char data8[32];
-\protected_separator
-
-\protected_separator
-
-\shape italic
-/* 8-bit data */
-\layout LyX-Code
-
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
- unsigned short data16[16];
-\protected_separator
-
-\shape italic
-/* 16-bit data */
-\layout LyX-Code
-
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
- unsigned int data32[8];
-\protected_separator
-
-\protected_separator
-
-\shape italic
-/* 32-bit data */
-\layout LyX-Code
-
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
- } value;
-\layout LyX-Code
-
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\shape italic
-/* reserved for future use \i \={ }
- must be zero !!! */
-\layout LyX-Code
-
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
- unsigned char reserved[32];
-\layout LyX-Code
-
-}
-\layout Subsubsection*
-
-int snd_rawmidi_output_switch_write(void *handle\i \c{ }
- int switchn\i \c{ }
- snd_rawmidi_switch_
-t *data)
-\layout Standard
-
-Writes the
-\shape italic
-*data
-\shape default
- structure with data about switch with index
-\shape italic
-switchn
-\shape default
- to kernel.
- Function returns zero if successful, otherwise it returns an error code.
-
-\layout Subsubsection*
-
-int snd_rawmidi_input_switches(void *handle)
-\layout Standard
-
-Returns count of rawmidi input switches.
- In this context 'switch' means universal control interface between kernel
- and application which allows various types of control.
- Function returns count if successful, otherwise it returns an error code.
- Return value should be zero if sound card doesn't have any rawmidi input
- switch.
-\layout Subsubsection*
-
-int snd_rawmidi_input_switch(void *handle, const char *switch_id)
-\layout Standard
-
-Returns index for switch with name
-\shape italic
-switch_id
-\shape default
-.
- Function returns switch index if successful, otherwise it returns an error
- code.
-\layout Subsubsection*
-
-int snd_rawmidi_input_switch_read(void *handle\i \c{ }
- int switchn\i \c{ }
- snd_rawmidi_switch_t
- *data)
-\layout Standard
-
-Fills the
-\shape italic
-*data
-\shape default
- structure with data about switch with index
-\shape italic
-switchn
-\shape default
-.
- Function returns zero if successful, otherwise it returns an error code.
-\layout Subsubsection*
-
-int snd_rawmidi_input_switch_write(void *handle\i \c{ }
- int switchn\i \c{ }
- snd_rawmidi_switch_t
- *data)
-\layout Standard
-
-Writes the
-\shape italic
-*data
-\shape default
- structure with data about switch with index
-\shape italic
-switchn
-\shape default
- to kernel.
- Function returns zero if successful, otherwise it returns an error code.
-
-\layout Subsubsection*
-
-int snd_rawmidi_output_params(void *handle, snd_rawmidi_output_params_t
- *params)
-\layout Standard
-
-Sets various parameters for output direction.
- Function returns zero if successful, otherwise it returns an error code.
-
-\layout LyX-Code
-
-struct snd_rawmidi_output_params {
-\layout LyX-Code
-
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
- int size;
-\layout LyX-Code
-
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
- int max;
-\layout LyX-Code
-
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
- int room;
-\layout LyX-Code
-
-
-\shape italic
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
- /* reserved for future use - must be filled with zero */
-\layout LyX-Code
-
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
- unsigned char reserved[16];
-\layout LyX-Code
-
-};
-\layout Description
-
-size Requested queue size of output buffer in bytes (default setup is 4096
- [i386] or 8192 [alpha] bytes - this is system architecture dependent).
-\layout Description
-
-max Maximum number of bytes in queue for wakeup.
- If the current byte count of filled portion of output buffer is greater
- than this value the driver will block an application or return immediately
- if non block mode is active.
-\layout Description
-
-room Minimum number of bytes writable for wakeup.
- This value should be in most cases 1 which means return back to application
- if at least one byte is free in output buffer.
-\layout Subsubsection*
-
-int snd_rawmidi_input_params(void *handle, snd_rawmidi_input_params_t *params)
-\layout Standard
-
-Function sets various parameters for the recording direction.
- Function returns zero if successful, otherwise it returns an error code.
-\layout LyX-Code
-
-struct snd_rawmidi_input_params {
-\layout LyX-Code
-
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
- int size;
-\layout LyX-Code
-
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
- int min;
-\layout LyX-Code
-
-
-\shape italic
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
- /* reserved for future use - must be filled with zero */
-\layout LyX-Code
-
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
- unsigned char reserved[16];
-\layout LyX-Code
-
-};
-\layout Description
-
-size Requested queue size of input buffer in bytes (default setup is 4096
- [i386] or 8192 [alpha] bytes - this is system architecture dependent).
-\layout Description
-
-min Minimum filled bytes in queue for wakeup.
- Driver blocks the application (if block mode is selected) until input buffer
- is filled with fewer than the number of bytes specified with this value.
-\layout Subsubsection*
-
-int snd_rawmidi_output_status(void *handle, snd_rawmidi_output_status_t
- *status)
-\layout Standard
-
-Fills the
-\shape italic
-*status
-\shape default
- structure.
- Function returns zero if successful, otherwise it returns an error code.
-\layout LyX-Code
-
-struct snd_rawmidi_output_status {
-\layout LyX-Code
-
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
- int size;
-\layout LyX-Code
-
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
- int count;
-\layout LyX-Code
-
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
- int queue;
-\layout LyX-Code
-
-
-\shape italic
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
- /* reserved for future use - must be filled with zero */
-\layout LyX-Code
-
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
- unsigned char reserved[16];
-\layout LyX-Code
-
-};
-\layout Description
-
-size Size of currently allocated queue in bytes.
-\layout Description
-
-count Count of bytes writable without blocking.
-\layout Description
-
-queue Count of bytes in queue (number of bytes waiting to be output).
-\layout Subsubsection*
-
-int snd_rawmidi_input_status(void *handle, snd_rawmidi_input_status_t *status)
-\layout Standard
-
-Fills the
-\shape italic
-*status
-\shape default
- structure.
- Function returns zero if successful, otherwise it returns an error code.
-\layout LyX-Code
-
-struct snd_rawmidi_input_status {
-\layout LyX-Code
-
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
- int size;
-\layout LyX-Code
-
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
- int count;
-\layout LyX-Code
-
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
- int free;
-\layout LyX-Code
-
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
- int overrun;
-\layout LyX-Code
-
-
-\shape italic
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
- /* reserved for future use - must be filled with zero */
-\layout LyX-Code
-
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
- unsigned char reserved[16];
-\layout LyX-Code
-
-};
-\layout Description
-
-size Size of currently allocated queue in bytes.
-\layout Description
-
-count Count of bytes readable without blocking.
-\layout Description
-
-free Count of bytes in queue still free.
-\layout Description
-
-overrun This value tells the application the count of overruns since the
- last call to
-\shape italic
-snd_rawmidi_input_status
-\shape default
-.
-\layout Subsubsection*
-
-int snd_rawmidi_drain_output(void *handle)
-\layout Standard
-
-This function stops and drains (destroys) the output queue immediately.
- Function returns zero if successful, otherwise it returns an error code.
-
-\layout Subsubsection*
-
-int snd_rawmidi_flush_output(void *handle)
-\layout Standard
-
-This function flushes the output queue.
- It blocks the program while the all the waiting bytes in kernel output
- queue are processed.
- Function returns zero if successful, otherwise it returns an error code.
-\layout Subsubsection*
-
-int snd_rawmidi_flush_input(void *handle)
-\layout Standard
-
-This function flushes (destroys) input queue.
- Function returns zero if successful, otherwise it returns an error code.
-
-\layout Subsubsection*
-
-ssize_t snd_rawmidi_write(void *handle, const void *buffer, size_t size)
-\layout Standard
-
-Writes bytes to the output queue.
- Function returns zero or positive value if the write was successful (value
- represents count of bytes which were successfully written to the device)
- or an error value if error occurred.
- Function will suspend the process if block mode is active.
-\layout Subsubsection*
-
-ssize_t snd_rawmidi_read(void *handle, void *buffer, size_t size)
-\layout Standard
-
-Function reads bytes from input queue.
- Function returns zero or positive value if the read was successful (value
- represents count of bytes which were successfully read from device) or
- negative error value if error occurred.
- Function will suspend the process if block mode is active.
-\layout Subsubsection
-
-Example
-\layout Standard
-
-The following example shows how to send a control sequence (such as SysEx)
- to a MIDI device.
- Sound card #0 and rawmidi device #0 are used here:
-\layout LyX-Code
-
-int card = 0, device = 0, err, fd, count, size;
-\layout LyX-Code
-
-void *handle;
-\layout LyX-Code
-
-snd_pcm_format_t format;
-\layout LyX-Code
-
-char *buffer;
-\layout Standard
-
-
-\protected_separator
-
-\layout LyX-Code
-
-buffer = (char *)malloc(64 * 1024);
-\layout LyX-Code
-
-if (!buffer) return;
-\layout LyX-Code
-
-if ((err = snd_rawmidi_open(&handle, card, device,
-\layout LyX-Code
-
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
- SND_RAWMIDI_OPEN_OUTPUT)) < 0) {
-\layout LyX-Code
-
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
- fprintf(stderr, "open failed: %s
-\backslash
-n", snd_strerror( err ));
-\layout LyX-Code
-
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
- return;
-\layout LyX-Code
-
-}
-\layout LyX-Code
-
-if ((err = snd_rawmidi_block_mode(handle\i \c{ }
- 1)) < 0) {
-\layout LyX-Code
-
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
- fprintf(stderr, "block failed: %s
-\backslash
-n", snd_strerror( err ));
-\layout LyX-Code
-
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
- snd_rawmidi_close(handle);
-\layout LyX-Code
-
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
- return;
-\layout LyX-Code
-
-}
-\layout LyX-Code
-
-fd = open("/tmp/test.sysex", O_RDONLY);
-\layout LyX-Code
-
-if (fd < 0) {
-\layout LyX-Code
-
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
- perror("open file");
-\layout LyX-Code
-
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
- snd_rawmidi_close(handle);
-\layout LyX-Code
-
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
- return;
-\layout LyX-Code
-
-}
-\layout LyX-Code
-
-idx = 0;
-\layout LyX-Code
-
-count = read(fd, buffer, 64 * 1024);
-\layout LyX-Code
-
-if (count <= 0) {
-\layout LyX-Code
-
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
- perror("read from file");
-\layout LyX-Code
-
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
- snd_rawmidi_close(handle);
-\layout LyX-Code
-
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
-
-\protected_separator
- return;
-\layout LyX-Code
-
-}
-\layout LyX-Code
-
-close(fd);
-\layout LyX-Code
-
-size = snd_rawmidi_write(handle, &buffer, count);
-\layout LyX-Code
-
-printf("Bytes written %i from %i...
-\backslash
-n", size, count);
-\layout LyX-Code
-
-snd_rawmidi_close(handle);
-\layout LyX-Code
-
-free(buffer);
-\the_end
git://git.alsa-project.org / alsa-lib.git / commitdiff
