On Tue, May 02, 2023 at 01:50:10PM +0200, Jaroslav Kysela wrote:
The application may not require to touch the sample stream for the drain operation at all. Handle this situation in alsa-lib.
i find this too vague.
This allows an application which uses an mmapped buffer to inform us that it is handling the silence padding itself.
Signed-off-by: Jaroslav Kysela perex@perex.cz
include/sound/uapi/asound.h | 3 +++ src/pcm/pcm.c | 32 ++++++++++++++++++++++++++++++++ src/pcm/pcm_hw.c | 3 ++- src/pcm/pcm_local.h | 1 + 4 files changed, 38 insertions(+), 1 deletion(-)
diff --git a/include/sound/uapi/asound.h b/include/sound/uapi/asound.h index 0b8834f2..f970179e 100644 --- a/include/sound/uapi/asound.h +++ b/include/sound/uapi/asound.h @@ -390,6 +390,9 @@ typedef int snd_pcm_hw_param_t; #define SNDRV_PCM_HW_PARAMS_NORESAMPLE (1<<0) /* avoid rate resampling */ #define SNDRV_PCM_HW_PARAMS_EXPORT_BUFFER (1<<1) /* export buffer */ #define SNDRV_PCM_HW_PARAMS_NO_PERIOD_WAKEUP (1<<2) /* disable period wakeups */ +#define SNDRV_PCM_HW_PARAMS_NO_DRAIN_SILENCE (1<<3) /* supress drain with the filling
* of the silence samples*/
"suppress automatic silence fill when draining playback"
--- a/src/pcm/pcm.c +++ b/src/pcm/pcm.c @@ -4958,6 +4958,38 @@ int snd_pcm_hw_params_get_period_wakeup(snd_pcm_t *pcm, snd_pcm_hw_params_t *par return 0; }
+/**
- \brief Restrict a configuration space to allow the drain with the
filling of silence samples
there is no way i'd understand what this means. in fact, i'm having a hard time even though i more or less know it already.
- \param pcm PCM handle
- \param params Configuration space
- \param val 0 = disable, 1 = enable (default) drain with the filling of silence samples
"padding the playback buffer with silence when drain() is invoked"
- \return 0 otherwise a negative error code
add description:
"When disabled, the application must ensure that enough samples are silenced, as most hardware will read beyond the application pointer when drain() is invoked."
+/**
- \brief Extract drain with the filling of silence samples from a configuration space
this is also kinda incomprehensible.
- \param pcm PCM handle
- \param params Configuration space
- \param val 0 = disable, 1 = enable
as this returns the status quo, this should be disabled/enabled.
- \return 0 otherwise a negative error code
there is no "otherwise" here.
- */
+int snd_pcm_hw_params_get_drain_silence(snd_pcm_t *pcm, snd_pcm_hw_params_t *params, unsigned int *val) +{
- assert(pcm && params && val);
- *val = params->flags & SND_PCM_HW_PARAMS_NO_DRAIN_SILENCE ? 0 : 1;
i know i'm paranoid, but i'd put extra parens around the condition.
- return 0;
+}
--- a/src/pcm/pcm_hw.c +++ b/src/pcm/pcm_hw.c @@ -399,7 +399,8 @@ static int snd_pcm_hw_hw_params(snd_pcm_t *pcm, snd_pcm_hw_params_t * params)
- hw->perfect_drain = !!(params->info & SND_PCM_INFO_PERFECT_DRAIN);
- hw->perfect_drain = !!(params->info & SND_PCM_INFO_PERFECT_DRAIN) ||
!!(params->flags & SND_PCM_HW_PARAMS_NO_DRAIN_SILENCE);
pedantically, you can remove the double negations as this point.
regards