From: Andreas Pape <apape@de.adit-jv.com>
Date: Tue, 22 Mar 2022 11:45:37 +0000 (+0100)
Subject: pcm: plugin - fix avail_min calculation on rate plugin
X-Git-Tag: v1.2.7~9
X-Git-Url: https://git.alsa-project.org/?a=commitdiff_plain;h=d21e0e01c66c627c38496027ba6757ea13e65999;p=alsa-lib.git

pcm: plugin - fix avail_min calculation on rate plugin

commit 88e4ae27, ff1f669d introduced a dynamic recalculation of the slave's
avail_min value.
The calculated avail_min setting did not take into account, that the avail_min value
depends on the used sampling rate and must be adapted accordingly
if the slave is using a different sampling rate.
That leads to too large/too small calculated avail_min settings and inaccurate
period wake-up events if a rate converter plugin is used.

This patch is adapting the avail_min calculation to consider a different
sampling rate between actual pcm and it's slave.

Fixes: https://github.com/alsa-project/alsa-lib/pull/218
Signed-off-by: Andreas Pape <apape@de.adit-jv.com>
Signed-off-by: Jaroslav Kysela <perex@perex.cz>
---

diff --git a/src/pcm/pcm_local.h b/src/pcm/pcm_local.h
index 8d25971f..d5393bc9 100644
--- a/src/pcm/pcm_local.h
+++ b/src/pcm/pcm_local.h
@@ -286,6 +286,8 @@ struct _snd_pcm {
 	snd1_pcm_wait_nocheck
 #define snd_pcm_rate_get_default_converter \
 	snd1_pcm_rate_get_default_converter
+#define snd_pcm_rate_slave_frames \
+	snd1_pcm_rate_slave_frames
 #define snd_pcm_set_hw_ptr \
 	snd1_pcm_set_hw_ptr
 #define snd_pcm_set_appl_ptr \
@@ -1009,6 +1011,8 @@ int snd_pcm_wait_nocheck(snd_pcm_t *pcm, int timeout);
 
 const snd_config_t *snd_pcm_rate_get_default_converter(snd_config_t *root);
 
+snd_pcm_uframes_t snd_pcm_rate_slave_frames(snd_pcm_t *pcm, snd_pcm_uframes_t frames);
+
 #define SND_PCM_HW_PARBIT_ACCESS	(1U << SND_PCM_HW_PARAM_ACCESS)
 #define SND_PCM_HW_PARBIT_FORMAT	(1U << SND_PCM_HW_PARAM_FORMAT)
 #define SND_PCM_HW_PARBIT_SUBFORMAT	(1U << SND_PCM_HW_PARAM_SUBFORMAT)
diff --git a/src/pcm/pcm_plugin.c b/src/pcm/pcm_plugin.c
index 24c9941d..7f934e8a 100644
--- a/src/pcm/pcm_plugin.c
+++ b/src/pcm/pcm_plugin.c
@@ -614,6 +614,14 @@ int snd_pcm_plugin_may_wait_for_avail_min(snd_pcm_t *pcm,
 			return 0;
 
 		needed_slave_avail_min = pcm->avail_min - available;
+
+		/* proportional adaption if rate converter is in place..
+		 * Can happen only on built-in rate plugin.
+		 * This code is also used by extplug, but extplug does not allow to alter the sampling rate.
+		 */
+		if (snd_pcm_type(pcm) == SND_PCM_TYPE_RATE)
+			needed_slave_avail_min = snd_pcm_rate_slave_frames(pcm, needed_slave_avail_min);
+
 		if (slave->avail_min != needed_slave_avail_min) {
 			snd_pcm_sw_params_t *swparams;
 			snd_pcm_sw_params_alloca(&swparams);
diff --git a/src/pcm/pcm_rate.c b/src/pcm/pcm_rate.c
index ba5364c0..9ba36eed 100644
--- a/src/pcm/pcm_rate.c
+++ b/src/pcm/pcm_rate.c
@@ -1343,6 +1343,25 @@ const snd_config_t *snd_pcm_rate_get_default_converter(snd_config_t *root)
 	return NULL;
 }
 
+/**
+ * \brief Convert rate pcm frames to corresponding rate slave pcm frames
+ * \param pcm PCM handle
+ * \param frames Frames to be converted to slave frames
+ * \retval Corresponding slave frames
+*/
+snd_pcm_uframes_t snd_pcm_rate_slave_frames(snd_pcm_t *pcm, snd_pcm_uframes_t frames)
+{
+	snd_pcm_uframes_t sframes;
+	snd_pcm_rate_t *rate = pcm->private_data;
+
+	if (pcm->stream == SND_PCM_STREAM_PLAYBACK)
+		sframes = rate->ops.output_frames(rate->obj, frames);
+	else
+		sframes = rate->ops.input_frames(rate->obj, frames);
+
+	return sframes;
+}
+
 static void rate_initial_setup(snd_pcm_rate_t *rate)
 {
 	if (rate->plugin_version == SND_PCM_RATE_PLUGIN_VERSION)