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@gmx.de Signed-off-by: Jaroslav Kysela perex@perex.cz --- 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);