[alsa-devel] snd_pcm_status_get_tstamp()

[Jaroslav Kysela]

On Mon, 7 Jan 2008, Takashi Iwai wrote:

> At Mon, 7 Jan 2008 16:21:55 +0100,
> Lennart Poettering wrote:
> > 
> > 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?
> 
> CLOCK_MONOTONIC is already available in the newer version of
> ALSA-driver.  But, the corresponding alsa-lib API isn't implemented
> yet.

Right. I will do this.

					Jaroslav

-----
Jaroslav Kysela <perex at perex.cz>
Linux Kernel Sound Maintainer
ALSA Project, Red Hat, Inc.