[alsa-devel] [BUG] snd_pcm_drop() does not stop the PCM immediately

[Takashi Iwai]

On Wed, 14 Mar 2018 15:59:07 +0100,
Martin Schreiber wrote:
> 
> Hi,
> The documentation states:
> "
> This function stops the PCM immediately. The pending samples on the
> buffer are ignored.
> "
> This does not work for the device "sysdefault" where a piece of the old
> sound and the new sound overlap, see attached alsadrop1.c testprogram.
> It is OK with the "default" device which is wired over Pulseaudio,
> uncomment alsadrop1.c:55 in order to test.
> The project is here:
> https://gitlab.com/mseide-msegui/mseuniverse/tree/master/testcase/audio/c/alsadrop
> 
> Environment: openSUSE Leap 42.3, see attached alsa-info.tar.gz.

It's a best-effort base stopping mechanism with dmix, so it's a sort
of expected behavior, unfortunately.  Due to its nature of
implementation, scratching off the existing data from the mixed buffer
isn't so trivial for now.


Takashi