* timestamps
@ 2010-04-21 11:00 Jonas Holmberg
2010-05-04 18:22 ` timestamps Kai Vehmanen
0 siblings, 1 reply; 2+ messages in thread
From: Jonas Holmberg @ 2010-04-21 11:00 UTC (permalink / raw)
To: alsa-devel
How can I get the CLOCK_MONOTONIC timestamp for the first sample in the
data I get from snd_pcm_readi()?
/Jonas
^ permalink raw reply [flat|nested] 2+ messages in thread
* Re: timestamps
2010-04-21 11:00 timestamps Jonas Holmberg
@ 2010-05-04 18:22 ` Kai Vehmanen
0 siblings, 0 replies; 2+ messages in thread
From: Kai Vehmanen @ 2010-05-04 18:22 UTC (permalink / raw)
To: Jonas Holmberg; +Cc: alsa-devel
Hi,
On Wed, 21 Apr 2010, Jonas Holmberg wrote:
> How can I get the CLOCK_MONOTONIC timestamp for the first sample in the
> data I get from snd_pcm_readi()?
before reading the data, take the current timestamp (with clock_gettime)
and subtract snd_pcm_delay() for the stream (see the API docs for
snd_pcm_delay() for more details).
The accuracy of the returned value depends on the driver/hw's ability to
report accurate delay values.
PS Alternate strategy is to use SND_PCM_TSTAMP_MMAP mode, in which
you can query (with snd_pcm_htimestamp()) the timestamp of
last period elapsed event. See the alsa-lib PCM API docs for
details. With certain drivers/hw, this is the only way to get
accurate estimates for delay.
^ permalink raw reply [flat|nested] 2+ messages in thread
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