RFC: Patch for alsa-lib. Not tested. For a discussion.
Some applications may not follow the period_size transfer blocks and
also the driver developers may not follow the consequeces of the
access beyond valid samples in the playback DMA buffer.
To avoid clicks, fill a little silence at the end of the playback
ring buffer when the snd_pcm_drain() is called.
TODO:
- add SND_PCM_NO_DRAIN_SILENCE as a new flag for snd_pcm_open()
- make this behaviour configurable (plugin config)
Cc: Oswald Buddenhagen <oswald.buddenhagen@xxxxxx>
Signed-off-by: Jaroslav Kysela <perex@xxxxxxxx>
---
src/pcm/pcm.c | 33 ++++++++++++++++++++-------------
src/pcm/pcm_hw.c | 45 +++++++++++++++++++++++++++++++++++++++++++++
src/pcm/pcm_local.h | 4 ++++
3 files changed, 69 insertions(+), 13 deletions(-)
diff --git a/src/pcm/pcm.c b/src/pcm/pcm.c
index 2b966d44..88b13ed4 100644
--- a/src/pcm/pcm.c
+++ b/src/pcm/pcm.c
@@ -6167,6 +6167,25 @@ int snd_pcm_hw_params_get_min_align(const snd_pcm_hw_params_t *params, snd_pcm_u
return 0;
}
+#ifndef DOXYGEN
+void snd_pcm_sw_params_current_no_lock(snd_pcm_t *pcm, snd_pcm_sw_params_t *params)
+{
+ params->proto = SNDRV_PCM_VERSION;
+ params->tstamp_mode = pcm->tstamp_mode;
+ params->tstamp_type = pcm->tstamp_type;
+ params->period_step = pcm->period_step;
+ params->sleep_min = 0;
+ params->avail_min = pcm->avail_min;
+ sw_set_period_event(params, pcm->period_event);
+ params->xfer_align = 1;
+ params->start_threshold = pcm->start_threshold;
+ params->stop_threshold = pcm->stop_threshold;
+ params->silence_threshold = pcm->silence_threshold;
+ params->silence_size = pcm->silence_size;
+ params->boundary = pcm->boundary;
+}
+#endif
+
/**
* \brief Return current software configuration for a PCM
* \param pcm PCM handle
@@ -6183,19 +6202,7 @@ int snd_pcm_sw_params_current(snd_pcm_t *pcm, snd_pcm_sw_params_t *params)
return -EIO;
}
__snd_pcm_lock(pcm); /* forced lock due to pcm field changes */
- params->proto = SNDRV_PCM_VERSION;
- params->tstamp_mode = pcm->tstamp_mode;
- params->tstamp_type = pcm->tstamp_type;
- params->period_step = pcm->period_step;
- params->sleep_min = 0;
- params->avail_min = pcm->avail_min;
- sw_set_period_event(params, pcm->period_event);
- params->xfer_align = 1;
- params->start_threshold = pcm->start_threshold;
- params->stop_threshold = pcm->stop_threshold;
- params->silence_threshold = pcm->silence_threshold;
- params->silence_size = pcm->silence_size;
- params->boundary = pcm->boundary;
+ snd_pcm_sw_params_current_no_lock(pcm, params);
__snd_pcm_unlock(pcm);
return 0;
}
diff --git a/src/pcm/pcm_hw.c b/src/pcm/pcm_hw.c
index daa3e1ff..4995b2cd 100644
--- a/src/pcm/pcm_hw.c
+++ b/src/pcm/pcm_hw.c
@@ -98,6 +98,8 @@ typedef struct {
bool mmap_control_fallbacked;
struct snd_pcm_sync_ptr *sync_ptr;
+ bool prepare_reset_sw_params;
+
int period_event;
snd_timer_t *period_timer;
struct pollfd period_timer_pfd;
@@ -534,6 +536,7 @@ static int snd_pcm_hw_sw_params(snd_pcm_t *pcm, snd_pcm_sw_params_t * params)
SYSMSG("SNDRV_PCM_IOCTL_SW_PARAMS failed (%i)", err);
goto out;
}
+ hw->prepare_reset_sw_params = false;
if ((snd_pcm_tstamp_type_t) params->tstamp_type != pcm->tstamp_type) {
if (hw->version < SNDRV_PROTOCOL_VERSION(2, 0, 12)) {
int on = (snd_pcm_tstamp_type_t) params->tstamp_type ==
@@ -660,7 +663,18 @@ static int snd_pcm_hw_hwsync(snd_pcm_t *pcm)
static int snd_pcm_hw_prepare(snd_pcm_t *pcm)
{
snd_pcm_hw_t *hw = pcm->private_data;
+ snd_pcm_sw_params_t sw_params;
int fd = hw->fd, err;
+
+ if (hw->prepare_reset_sw_params) {
+ snd_pcm_sw_params_current_no_lock(pcm, &sw_params);
+ if (ioctl(hw->fd, SNDRV_PCM_IOCTL_SW_PARAMS, sw_params) < 0) {
+ err = -errno;
+ SYSMSG("SNDRV_PCM_IOCTL_SW_PARAMS failed (%i)", err);
+ return err;
+ }
+ hw->prepare_reset_sw_params = false;
+ }
if (ioctl(fd, SNDRV_PCM_IOCTL_PREPARE) < 0) {
err = -errno;
SYSMSG("SNDRV_PCM_IOCTL_PREPARE failed (%i)", err);
@@ -718,7 +732,38 @@ static int snd_pcm_hw_drop(snd_pcm_t *pcm)
static int snd_pcm_hw_drain(snd_pcm_t *pcm)
{
snd_pcm_hw_t *hw = pcm->private_data;
+ snd_pcm_sw_params_t sw_params;
+ snd_pcm_uframes_t silence_size;
int err;
+
+ if (pcm->stream != SND_PCM_STREAM_PLAYBACK)
+ goto __skip_silence;
+ /* compute end silence size, align to period size + extra time */
+ snd_pcm_sw_params_current_no_lock(pcm, &sw_params);
+ if ((pcm->buffer_size % pcm->period_size) == 0) {
+ silence_size = pcm->period_size - (pcm->period_size % *pcm->appl.ptr);
+ if (silence_size == pcm->period_size)
+ silence_size = 0;
+ } else {
+ /* it not not easy to compute the period cross point
+ * in this case because boundary is aligned only
+ * to the buffer_size - use the full range (period)
+ */
+ silence_size = pcm->period_size;
+ }
+ silence_size += pcm->rate / 10; /* 1/10th of second */
+ if (sw_params.silence_size < silence_size) {
+ /* fill silence soon as possible (in the bellow ioctl) */
+ sw_params.silence_threshold = pcm->buffer_size;
+ sw_params.silence_size = silence_size;
+ if (ioctl(hw->fd, SNDRV_PCM_IOCTL_SW_PARAMS, sw_params) < 0) {
+ err = -errno;
+ SYSMSG("SNDRV_PCM_IOCTL_SW_PARAMS failed (%i)", err);
+ return err;
+ }
+ hw->prepare_reset_sw_params = true;
+ }
+__skip_silence:
if (ioctl(hw->fd, SNDRV_PCM_IOCTL_DRAIN) < 0) {
err = -errno;
SYSMSG("SNDRV_PCM_IOCTL_DRAIN failed (%i)", err);
diff --git a/src/pcm/pcm_local.h b/src/pcm/pcm_local.h
index ae0c44bf..4a859cd1 100644
--- a/src/pcm/pcm_local.h
+++ b/src/pcm/pcm_local.h
@@ -366,6 +366,8 @@ struct _snd_pcm {
snd1_pcm_hw_param_get_max
#define snd_pcm_hw_param_name \
snd1_pcm_hw_param_name
+#define snd_pcm_sw_params_current_no_lock \
+ snd1_pcm_sw_params_current_no_lock
int snd_pcm_new(snd_pcm_t **pcmp, snd_pcm_type_t type, const char *name,
snd_pcm_stream_t stream, int mode);
@@ -390,6 +392,8 @@ void snd_pcm_mmap_appl_forward(snd_pcm_t *pcm, snd_pcm_uframes_t frames);
void snd_pcm_mmap_hw_backward(snd_pcm_t *pcm, snd_pcm_uframes_t frames);
void snd_pcm_mmap_hw_forward(snd_pcm_t *pcm, snd_pcm_uframes_t frames);
+void snd_pcm_sw_params_current_no_lock(snd_pcm_t *pcm, snd_pcm_sw_params_t *params);
+
snd_pcm_sframes_t snd_pcm_mmap_writei(snd_pcm_t *pcm, const void *buffer, snd_pcm_uframes_t size);
snd_pcm_sframes_t snd_pcm_mmap_readi(snd_pcm_t *pcm, void *buffer, snd_pcm_uframes_t size);
snd_pcm_sframes_t snd_pcm_mmap_writen(snd_pcm_t *pcm, void **bufs, snd_pcm_uframes_t size);
--
2.39.2
