[alsa-devel] snd_pcm_status_get_tstamp()

[Lennart Poettering]

On Mon, 07.01.08 12:10, Takashi Iwai (tiwai at suse.de) wrote:

> > The documentation for snd_pcm_status_get_tstamp() is not really
> > enlightening. After a call to snd_pcm_status() what data does the
> > tstamp field actually carry? Some kind of system clock timestamp when
> > the data in the status struct was valid, or some kind of sound card
> > clock timestamp that is relative to the point in time where the device
> > was opened/started?
> 
> In the normal mode, it's the timestamp at the moment snd_pcm_status()
> is processed.  OTOH, the trigger_tstamp is the time that the trigger
> callback was called (e.g. the stream starts / stops).
> The time is the system-wide time, equivalent with the normal
> gettimeofday().

So I figure this is always CLOCK_REALTIME?

I am currently using CLOCK_MONOTONIC for most timekeeping in
PulseAudio. Would it be possible to add an API to ALSA to allow
getting those timestamps in CLOCK_MONOTONIC instead of CLOCK_REALTIME?

Maybe by adding two new time stamp modes, changeble via
snd_pcm_sw_params_set_tstamp_mode()?

Also, may I suggest to add the explanation you wrote above to the
doxygen docs?

Thanks,

Lennart

-- 
Lennart Poettering                        Red Hat, Inc.
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