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pcm: support for audio timestamps

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add new snd_pcm_status_get_audio_htstamp() routine to
query the audio timestamps provided by the kernel.

This change provides applications with better ways
to track elapsed time. Before this patch, applications
would subtract queued samples (delay) from written samples,
resulting in a 1-2 sample error.

Also add snd_pcm_hw_params_supports_audio_wallclock_ts()
to query what the hardware supports.

TODO: check protocol compatibility?

Signed-off-by: Pierre-Louis Bossart <pierre-louis.bossart@linux.intel.com>
Signed-off-by: Takashi Iwai <tiwai@suse.de>
This commit is contained in:
Pierre-Louis Bossart 2012-06-12 14:36:40 -05:00 • committed by Takashi Iwai
parent 4bdb09126a
commit cf40ea169a
4 changed files with 96 additions and 12 deletions
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2
include/pcm.h
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@ -631,6 +631,7 @@ int snd_pcm_hw_params_is_half_duplex(const snd_pcm_hw_params_t *params);
int snd_pcm_hw_params_is_joint_duplex(const snd_pcm_hw_params_t *params);
int snd_pcm_hw_params_can_sync_start(const snd_pcm_hw_params_t *params);
int snd_pcm_hw_params_can_disable_period_wakeup(const snd_pcm_hw_params_t *params);
int snd_pcm_hw_params_supports_audio_wallclock_ts(const snd_pcm_hw_params_t *params);
int snd_pcm_hw_params_get_rate_numden(const snd_pcm_hw_params_t *params,
unsigned int *rate_num,
unsigned int *rate_den);
@ -939,6 +940,7 @@ void snd_pcm_status_get_trigger_tstamp(const snd_pcm_status_t *obj, snd_timestam
void snd_pcm_status_get_trigger_htstamp(const snd_pcm_status_t *obj, snd_htimestamp_t *ptr);
void snd_pcm_status_get_tstamp(const snd_pcm_status_t *obj, snd_timestamp_t *ptr);
void snd_pcm_status_get_htstamp(const snd_pcm_status_t *obj, snd_htimestamp_t *ptr);
void snd_pcm_status_get_audio_htstamp(const snd_pcm_status_t *obj, snd_htimestamp_t *ptr);
snd_pcm_sframes_t snd_pcm_status_get_delay(const snd_pcm_status_t *obj);
snd_pcm_uframes_t snd_pcm_status_get_avail(const snd_pcm_status_t *obj);
snd_pcm_uframes_t snd_pcm_status_get_avail_max(const snd_pcm_status_t *obj);