[Portaudio] PaGetStreamTime apparently always returns 0

sqweek sqweek at gmail.com
Tue Dec 22 08:45:42 EST 2015


On 22 December 2015 at 00:07, Nicolas Castagne <nicolas.castagne at imag.fr>
wrote:

> Hello everyone,
>
> Thanks for your answers Ross and Alan.
> Sorry I could not answer back sooner (almost 2 months w/o any answer from
> me !).
>
> I confirm a "Pa_GetStreamTime() bug related to pulse audio" Ross, as you
> suggested.
>
> Where and how should I fill a bug report ?
>
> Basically :
>
> -> On all our Linux machines, when using
> PulseAudio, Pa_GetStreamTime() returns an error (=> returns 0., as
> mentioned in PA documentation).
> Apparently, PulseAudio doesn't implement timestamps
>
> -> Using an alsa device not based on Pulse fixes the issue
>
> -> Uninstalling pulse audio fixes the pb on the default device (but of
> course triggers others)
>

The problem is not that pulse audio doesn't provide timestamps (it does) -
the problem is these timestamps are not plumbed through to ALSA when using
the pulse ALSA pcm plugin.

Since portaudio doesn't (yet) support pulse audio as a host API, it needs
to go through ALSA and therefore can't get the timing information.

I reported this previously on the pulse audio bugzilla:
https://bugs.freedesktop.org/show_bug.cgi?id=88503

But really it's an ALSA bug. I've reported it to the alsa-devel mailing
list:

http://mailman.alsa-project.org/pipermail/alsa-devel/2015-February/087353.html

And it has been acknowledged as functionality not yet implemented:

http://mailman.alsa-project.org/pipermail/alsa-devel/2015-September/097944.html

I don't know if ALSA has another bug tracking mechanism.

You might also be interested in Tuukka Pasanen's recent work toward
implementing a pulseaudio host API for port audio - announced on this
mailing list a few weeks ago:

https://lists.columbia.edu/pipermail/portaudio/2015-December/000201.html

-sqweek
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