pcm: iec958: implement HDMI HBR audio formatting

High bitrate compressed audio data like DTS HD or MAT is usually
packed into 8-channel data. The HDMI specs state this has to be
formatted as a single IEC958 stream, compared to normal multi-
channel PCM data which has to be formatted as parallel IEC958 streams.

As this single-stream formatting mode may break existing setups that
expect non-PCM multichannel data to be formatted as parallel IEC958
streams it needs to be explicitly selected by setting the hdmi_mode
option to true.

The single-stream formatting implementation is prepared to cope with
arbitrary channel counts but only limited testing was done for channel
counts other than 8.

Signed-off-by: Matthias Reichl <hias@horus.com>
Signed-off-by: Takashi Iwai <tiwai@suse.de>

diff --git a/src/pcm/pcm_iec958.c b/src/pcm/pcm_iec958.c
index 76d3ca7b8e3cf76d2d66520cb3331004ac5ccc8c..17ade9571cae3f82152aac02af977e22d1c12fdf 100644 (file)
--- a/src/pcm/pcm_iec958.c
+++ b/src/pcm/pcm_iec958.c
@@ -63,6 +63,7 @@ struct snd_pcm_iec958 {
        unsigned int byteswap;
        unsigned char preamble[3];      /* B/M/W or Z/X/Y */
        snd_pcm_fast_ops_t fops;
+       int hdmi_mode;
 };
 
 enum { PREAMBLE_Z, PREAMBLE_X, PREAMBLE_Y };
@@ -193,6 +194,10 @@ static void snd_pcm_iec958_encode(snd_pcm_iec958_t *iec,
        unsigned int channel;
        int32_t sample = 0;
        int counter = iec->counter;
+       int single_stream = iec->hdmi_mode &&
+                           (iec->status[0] & IEC958_AES0_NONAUDIO) &&
+                           (channels == 8);
+       int counter_step = single_stream ? ((channels + 1) >> 1) : 1;
        for (channel = 0; channel < channels; ++channel) {
                const char *src;
                uint32_t *dst;
@@ -205,7 +210,12 @@ static void snd_pcm_iec958_encode(snd_pcm_iec958_t *iec,
                src_step = snd_pcm_channel_area_step(src_area);
                dst_step = snd_pcm_channel_area_step(dst_area) / sizeof(uint32_t);
                frames1 = frames;
-               iec->counter = counter;
+
+               if (single_stream)
+                       iec->counter = (counter + (channel >> 1)) % 192;
+               else
+                       iec->counter = counter;
+
                while (frames1-- > 0) {
                        goto *get;
 #define GET32_END after
@@ -217,9 +227,11 @@ static void snd_pcm_iec958_encode(snd_pcm_iec958_t *iec,
                        *dst = sample;
                        src += src_step;
                        dst += dst_step;
-                       iec->counter++;
+                       iec->counter += counter_step;
                        iec->counter %= 192;
                }
+               if (single_stream) /* set counter to ch0 value for next iteration */
+                       iec->counter = (counter + frames * counter_step) % 192;
        }
 }
 #endif /* DOC_HIDDEN */
@@ -473,6 +485,7 @@ static const snd_pcm_ops_t snd_pcm_iec958_ops = {
  * \param close_slave When set, the slave PCM handle is closed with copy PCM
  * \param status_bits The IEC958 status bits
  * \param preamble_vals The preamble byte values
+ * \param hdmi_mode When set, enable HDMI compliant formatting
  * \retval zero on success otherwise a negative error code
  * \warning Using of this function might be dangerous in the sense
  *          of compatibility reasons. The prototype might be freely
@@ -481,7 +494,8 @@ static const snd_pcm_ops_t snd_pcm_iec958_ops = {
 int snd_pcm_iec958_open(snd_pcm_t **pcmp, const char *name, snd_pcm_format_t sformat,
                        snd_pcm_t *slave, int close_slave,
                        const unsigned char *status_bits,
-                       const unsigned char *preamble_vals)
+                       const unsigned char *preamble_vals,
+                       int hdmi_mode)
 {
        snd_pcm_t *pcm;
        snd_pcm_iec958_t *iec;
@@ -519,6 +533,8 @@ int snd_pcm_iec958_open(snd_pcm_t **pcmp, const char *name, snd_pcm_format_t sfo
 
        memcpy(iec->preamble, preamble_vals, 3);
 
+       iec->hdmi_mode = hdmi_mode;
+
        err = snd_pcm_new(&pcm, SND_PCM_TYPE_IEC958, name, slave->stream, slave->mode);
        if (err < 0) {
                free(iec);
@@ -566,9 +582,14 @@ pcm.name {
        [preamble.z or preamble.b val]
        [preamble.x or preamble.m val]
        [preamble.y or preamble.w val]
+       [hdmi_mode true]
 }
 \endcode
 
+When <code>hdmi_mode</code> is true, 8-channel compressed data is
+formatted as 4 contiguous frames of a single IEC958 stream as required
+by the HDMI HBR specification.
+
 \subsection pcm_plugins_iec958_funcref Function reference
 
 <UL>
@@ -605,6 +626,7 @@ int _snd_pcm_iec958_open(snd_pcm_t **pcmp, const char *name,
        unsigned char preamble_vals[3] = {
                0x08, 0x02, 0x04 /* Z, X, Y */
        };
+       int hdmi_mode = 0;
 
        snd_config_for_each(i, next, conf) {
                snd_config_t *n = snd_config_iterator_entry(i);
@@ -633,6 +655,13 @@ int _snd_pcm_iec958_open(snd_pcm_t **pcmp, const char *name,
                        preamble = n;
                        continue;
                }
+               if (strcmp(id, "hdmi_mode") == 0) {
+                       err = snd_config_get_bool(n);
+                       if (err < 0)
+                               continue;
+                       hdmi_mode = err;
+                       continue;
+               }
                SNDERR("Unknown field %s", id);
                return -EINVAL;
        }
@@ -707,7 +736,7 @@ int _snd_pcm_iec958_open(snd_pcm_t **pcmp, const char *name,
                return err;
        err = snd_pcm_iec958_open(pcmp, name, sformat, spcm, 1,
                                  status ? status_bits : NULL,
-                                 preamble_vals);
+                                 preamble_vals, hdmi_mode);
        if (err < 0)
                snd_pcm_close(spcm);
        return err;