diff options
| author | Pierre-Louis Bossart <pierre-louis.bossart@linux.intel.com> | 2012-10-22 16:42:15 -0500 |
|---|---|---|
| committer | Takashi Iwai <tiwai@suse.de> | 2012-10-23 16:13:48 +0200 |
| commit | 4eeaaeaea1cec60a25979678182720dc91308550 (patch) | |
| tree | ef6895d3ff86454cc6348e2efde2313eceb24471 /sound/core/pcm_native.c | |
| parent | 0e8014d772a7639f48d234b23dc4ce97335cce7f (diff) | |
ALSA: core: add hooks for audio timestamps
ALSA did not provide any direct means to infer the audio time for A/V
sync and system/audio time correlations (eg. PulseAudio).
Applications had to track the number of samples read/written and
add/subtract the number of samples queued in the ring buffer. This
accounting led to small errors, typically several samples, due to the
two-step process. Computing the audio time in the kernel is more
direct, as all the information is available in the same routines.
Also add new .audio_wallclock routine to enable fine-grain synchronization
between monotonic system time and audio hardware time.
Using the wallclock, if supported in hardware, allows for a
much better sub-microsecond precision and a common drift tracking for
all devices sharing the same wall clock (master clock).
Signed-off-by: Pierre-Louis Bossart <pierre-louis.bossart@linux.intel.com>
Signed-off-by: Takashi Iwai <tiwai@suse.de>
Diffstat (limited to 'sound/core/pcm_native.c')
| -rw-r--r-- | sound/core/pcm_native.c | 2 |
1 files changed, 2 insertions, 0 deletions
diff --git a/sound/core/pcm_native.c b/sound/core/pcm_native.c index 5e12e5bacbba..7c800012fff9 100644 --- a/sound/core/pcm_native.c +++ b/sound/core/pcm_native.c @@ -594,6 +594,8 @@ int snd_pcm_status(struct snd_pcm_substream *substream, snd_pcm_update_hw_ptr(substream); if (runtime->tstamp_mode == SNDRV_PCM_TSTAMP_ENABLE) { status->tstamp = runtime->status->tstamp; + status->audio_tstamp = + runtime->status->audio_tstamp; goto _tstamp_end; } } |