At Mon, 8 Oct 2012 12:11:57 -0500, Pierre-Louis Bossart wrote:
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
include/sound/asound.h | 7 +++++-- include/sound/pcm.h | 2 ++ sound/core/pcm_compat.c | 13 +++++++++++-- sound/core/pcm_lib.c | 32 ++++++++++++++++++++++++++++++-- sound/core/pcm_native.c | 2 ++ 5 files changed, 50 insertions(+), 6 deletions(-)
diff --git a/include/sound/asound.h b/include/sound/asound.h index 0876a1e..2d1ba63 100644 --- a/include/sound/asound.h +++ b/include/sound/asound.h @@ -152,7 +152,7 @@ struct snd_hwdep_dsp_image {
******************************************************************************/
-#define SNDRV_PCM_VERSION SNDRV_PROTOCOL_VERSION(2, 0, 10) +#define SNDRV_PCM_VERSION SNDRV_PROTOCOL_VERSION(2, 0, 11)
typedef unsigned long snd_pcm_uframes_t; typedef signed long snd_pcm_sframes_t; @@ -274,6 +274,7 @@ typedef int __bitwise snd_pcm_subformat_t; #define SNDRV_PCM_INFO_JOINT_DUPLEX 0x00200000 /* playback and capture stream are somewhat correlated */ #define SNDRV_PCM_INFO_SYNC_START 0x00400000 /* pcm support some kind of sync go */ #define SNDRV_PCM_INFO_NO_PERIOD_WAKEUP 0x00800000 /* period wakeup can be disabled */ +#define SNDRV_PCM_INFO_HAS_WALL_CLOCK 0x01000000 /* has audio wall clock for audio/system time sync */ #define SNDRV_PCM_INFO_FIFO_IN_FRAMES 0x80000000 /* internal kernel flag - FIFO size is in frames */
typedef int __bitwise snd_pcm_state_t; @@ -422,7 +423,8 @@ struct snd_pcm_status { snd_pcm_uframes_t avail_max; /* max frames available on hw since last status */ snd_pcm_uframes_t overrange; /* count of ADC (capture) overrange detections from last status */ snd_pcm_state_t suspended_state; /* suspended stream state */
- unsigned char reserved[60]; /* must be filled with zero */
- struct timespec audio_tstamp; /* from sample counter or wall clock */
- unsigned char reserved[60-sizeof(struct timespec)]; /* must be filled with zero */
};
struct snd_pcm_mmap_status { @@ -431,6 +433,7 @@ struct snd_pcm_mmap_status { snd_pcm_uframes_t hw_ptr; /* RO: hw ptr (0...boundary-1) */ struct timespec tstamp; /* Timestamp */ snd_pcm_state_t suspended_state; /* RO: suspended stream state */
- struct timespec audio_tstamp; /* from sample counter or wall clock */
};
struct snd_pcm_mmap_control { diff --git a/include/sound/pcm.h b/include/sound/pcm.h index ba13e0b..e2f1d48 100644 --- a/include/sound/pcm.h +++ b/include/sound/pcm.h @@ -71,6 +71,8 @@ struct snd_pcm_ops { int (*prepare)(struct snd_pcm_substream *substream); int (*trigger)(struct snd_pcm_substream *substream, int cmd); snd_pcm_uframes_t (*pointer)(struct snd_pcm_substream *substream);
- int (*wall_clock)(struct snd_pcm_substream *substream,
struct timespec *audio_ts);diff --git a/sound/core/pcm_compat.c b/sound/core/pcm_compat.c index 91cdf94..ab4c953 100644 --- a/sound/core/pcm_compat.c +++ b/sound/core/pcm_compat.c @@ -190,7 +190,8 @@ struct snd_pcm_status32 { u32 avail_max; u32 overrange; s32 suspended_state;
- unsigned char reserved[60];
- struct timespec audio_tstamp;
It must be struct compat_timespec...
- unsigned char reserved[60-sizeof(struct timespec)];
} __attribute__((packed));
@@ -215,7 +216,9 @@ static int snd_pcm_status_user_compat(struct snd_pcm_substream *substream, put_user(status.avail, &src->avail) || put_user(status.avail_max, &src->avail_max) || put_user(status.overrange, &src->overrange) ||
put_user(status.suspended_state, &src->suspended_state))
put_user(status.suspended_state, &src->suspended_state) ||put_user(status.audio_tstamp.tv_sec, &src->audio_tstamp.tv_sec) ||put_user(status.audio_tstamp.tv_nsec, &src->audio_tstamp.tv_nsec))
... and use compat_put_timespec().
return -EFAULT;return err; @@ -364,6 +367,7 @@ struct snd_pcm_mmap_status32 { u32 hw_ptr; struct compat_timespec tstamp; s32 suspended_state;
- struct compat_timespec audio_tstamp;
Ditto.
} __attribute__((packed));
struct snd_pcm_mmap_control32 { @@ -426,12 +430,17 @@ static int snd_pcm_ioctl_sync_ptr_compat(struct snd_pcm_substream *substream, sstatus.hw_ptr = status->hw_ptr % boundary; sstatus.tstamp = status->tstamp; sstatus.suspended_state = status->suspended_state;
- sstatus.audio_tstamp = status->audio_tstamp; snd_pcm_stream_unlock_irq(substream); if (put_user(sstatus.state, &src->s.status.state) || put_user(sstatus.hw_ptr, &src->s.status.hw_ptr) || put_user(sstatus.tstamp.tv_sec, &src->s.status.tstamp.tv_sec) || put_user(sstatus.tstamp.tv_nsec, &src->s.status.tstamp.tv_nsec) || put_user(sstatus.suspended_state, &src->s.status.suspended_state) ||
put_user(sstatus.audio_tstamp.tv_sec,&src->s.status.audio_tstamp.tv_sec) ||put_user(sstatus.audio_tstamp.tv_nsec,&src->s.status.audio_tstamp.tv_nsec) ||
Ditto.
Takashi
put_user(scontrol.appl_ptr, &src->c.control.appl_ptr) || put_user(scontrol.avail_min, &src->c.control.avail_min)) return -EFAULT;diff --git a/sound/core/pcm_lib.c b/sound/core/pcm_lib.c index ec996ca..2bccd16 100644 --- a/sound/core/pcm_lib.c +++ b/sound/core/pcm_lib.c @@ -315,6 +315,7 @@ static int snd_pcm_update_hw_ptr0(struct snd_pcm_substream *substream, unsigned long jdelta; unsigned long curr_jiffies; struct timespec curr_tstamp;
struct timespec audio_tstamp; int crossed_boundary = 0;
old_hw_ptr = runtime->status->hw_ptr;
@@ -327,9 +328,14 @@ static int snd_pcm_update_hw_ptr0(struct snd_pcm_substream *substream, */ pos = substream->ops->pointer(substream); curr_jiffies = jiffies;
- if (runtime->tstamp_mode == SNDRV_PCM_TSTAMP_ENABLE)
if (runtime->tstamp_mode == SNDRV_PCM_TSTAMP_ENABLE) { snd_pcm_gettime(runtime, (struct timespec *)&curr_tstamp);
if ((runtime->hw.info & SNDRV_PCM_INFO_HAS_WALL_CLOCK) &&(substream->ops->wall_clock))substream->ops->wall_clock(substream, &audio_tstamp);}
if (pos == SNDRV_PCM_POS_XRUN) { xrun(substream); return -EPIPE;
@@ -520,9 +526,31 @@ static int snd_pcm_update_hw_ptr0(struct snd_pcm_substream *substream, BUG_ON(crossed_boundary < 0); runtime->hw_ptr_wrap += runtime->boundary; }
- if (runtime->tstamp_mode == SNDRV_PCM_TSTAMP_ENABLE)
if (runtime->tstamp_mode == SNDRV_PCM_TSTAMP_ENABLE) { runtime->status->tstamp = curr_tstamp;
if (!(runtime->hw.info & SNDRV_PCM_INFO_HAS_WALL_CLOCK)) {/** no wall clock available, provide audio timestamp* derived from pointer position+delay*/u64 audio_frames, audio_nsecs;if (substream->stream == SNDRV_PCM_STREAM_PLAYBACK)audio_frames = runtime->hw_ptr_wrap+ runtime->status->hw_ptr- runtime->delay;elseaudio_frames = runtime->hw_ptr_wrap+ runtime->status->hw_ptr+ runtime->delay;audio_nsecs = div_u64(audio_frames * 1000000000LL,runtime->rate);audio_tstamp = ns_to_timespec(audio_nsecs);}runtime->status->audio_tstamp = audio_tstamp;}
return snd_pcm_update_state(substream, runtime);
}
diff --git a/sound/core/pcm_native.c b/sound/core/pcm_native.c index 53b5ada..c5206f4 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;-- 1.7.9.5
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