[Bug 677346] New: PulseAudio can't be "unmuted" correctly when Alsa is also enabled.

[GStreamer (bugzilla.gnome.org)]

https://bugzilla.gnome.org/show_bug.cgi?id=677346
  GStreamer | don't know | 0.10.36

           Summary: PulseAudio can't be "unmuted" correctly when Alsa is
                    also enabled.
    Classification: Platform
           Product: GStreamer
           Version: 0.10.36
        OS/Version: Linux
            Status: UNCONFIRMED
          Severity: minor
          Priority: Normal
         Component: don't know
        AssignedTo: gstreamer-bugs at lists.freedesktop.org
        ReportedBy: kaodome at gmail.com
         QAContact: gstreamer-bugs at lists.freedesktop.org
     GNOME version: ---


Hi, I was tracking what I thought was a bug in xfce4-volumed at first but it
turned out to be GStreamer related, but the code in GStreamer was pretty
complicated to understand not knowing much about it. xfce4-volumed is just a
helper to bind multimedia keys to perform actions like mute or volume up and
down in XFCE.

When the mute key is pressed, the output is muted via a call to
gst_mixer_set_mute(). I was inspecting the relevant code in that application
and it looks correct to me, so I used a little helper to check several
properties of the available mixers in GStreamer.

There were a couple although the relevant ones were 2: an ALSA one an a
PulseAudio one, both being outputs and having a "master" track.

Upon pressing the mute key and displaying the notification the volume was
effectively muted and both mixers got the GST_MIXER_TRACK_MUTE flag active.

Pressing the mute key again to return the volume to where it was, "unmute", the
ALSA mixer was unmuted (GST_MIXER_TRACK_MUTE flag was false) but the PulseAudio
mixer had that flag still true, and effectively being muted. The only way to
unmute it was through pavucontrol (PulseAudio volume control application).

After reading through the code and trying some things I decided to recompile
Gstreamer -base and -base-plugins without ALSA support (--disable-alsa
configure flag). When listing the mixers in GStreamer only PulseAudio ones
where available (the output one and 2 input), and now the mute/unmute
functionality works as expected.

There was a commit in Gstreamer -good related to PulseAudio recently which
fixed something mute related too but I recon it doesn't matter in this bug:
http://cgit.freedesktop.org/gstreamer/gst-plugins-good/commit/?id=e7240413a7b678cc89c0b68cf15d68c7f14d921a

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