[alsa-devel] [PATCH] Two patches for Alsa-plugins (pulse)

[Raymond Yau]

2010/7/9 Takashi Iwai <tiwai at suse.de>

> At Mon, 05 Jul 2010 08:06:45 +0200,
> I wrote:
> >
> > At Fri, 25 Jun 2010 12:41:46 +0200,
> > David Henningsson wrote:
> > >
> > > On 2010-06-24 08:42, Takashi Iwai wrote:
> > > > At Wed, 23 Jun 2010 21:57:01 +0200,
> > > > David Henningsson wrote:
> > > >>
> > > >> These two patches are being used in Ubuntu Lucid (released this
> April)
> > > >> and are working well enough to have people asking us to backport
> them to
> > > >> Karmic. Today I got an email, asking for the upstream status of one
> of
> > > >> these patches, since he wanted them in Fedora. If posting them here
> > > >> isn't the correct way to upstream them, please tell me so.
> > > >>
> > > >> The first one (Fix invalid buffer pointer return value) fixes broken
> logic:
> > > >>
> > > >> This patch improves recovering from underruns, and prevents hangs
> inside
> > > >> snd_pcm_write* and snd_pcm_read* due to snd_pcm_avail* returning too
> > > >> low values. It especially helps low latency situations.
> > > >
> > > > This one looks OK.  Applied now.
> > >
> > > Thanks!
> > >
> > > >> The second one (Do not report underruns to the ALSA layer) is more a
> > > >> change of behavior, which could be questioned. The arguments for
> > > >> removing that code are these:
> > > >>
> > > >>  * If pulseaudio gets an underrun, the normal way to end that
> underrun
> > > >> is to feed it with more buffers. This is different from the ALSA way
> of
> > > >> dealing with underruns, which requires hardware buffer pointers to
> be reset.
> > > >>  * In addition, underrun signals are delivered asynchronously from
> > > >> pulseaudio. This means that there might be more buffers on the way
> to
> > > >> pulseaudio when the underrun is reported, making the underrun
> obsolete.
> > > >> Unfortunately, there is currently no known way to determine whether
> this
> > > >> is the case or not.
> > > >
> > > > I think this helps for normal use-cases, so it'd be good to apply.
> > > > But, I prefer having a runtime option for such a behavior change
> > > > (although the default value can be the new behavior).
> > > >
> > > > Care to add it?
> > >
> > > Sure, I can do that - it sounds like a good idea to have it
> configurable.
> > > Just so I understand you right, exactly how do you expect the user /
> > > application to configure it?
> >
> > I suppose it can be simply added as an alsa-lib plugin config, i.e.
> > in SND_PCM_PLUGIN_DEFINE_FUNC(pulse) of alsa-plugins/pulse/pcm_pulse.c,
> > add the code like below:
> >
> >       int handle_underrun = 0;
> >       ...
> >
> >       snd_config_for_each(i, next, conf) {
> >               ...
> >               if (strcmp(id, "handle_underrun") == 0) {
> >                       handle_underrun = snd_config_get_bool(n);
> >                       if (handle_underrun < 0) {
> >                               SNDERR("Invalid value for %s", id);
> >                               return handle_underrun;
> >                       }
> >                       continue;
> >               }
> >       }
>
> FYI, I modified the patch and applied to git tree right now.
>
>
> thanks,
>
> Takashi
>


This behaviour is a little bit strange , using the same buffer size 128

aplay -Dhw:0,0 --buffer-size=128 test.wav

report underrun


aplay -D pulse --buffer-size=128 test.wav

did not report underrun but the sound is distorted