[gstreamer-bugs] [Bug 486840] New: Use _all variants when setting the mixer

[GStreamer (bugzilla.gnome.org)]

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  GStreamer | gst-plugins-base | Ver: HEAD CVS
           Summary: Use _all variants when setting the mixer
           Product: GStreamer
           Version: HEAD CVS
          Platform: Other
        OS/Version: Linux
            Status: UNCONFIRMED
          Severity: normal
          Priority: Normal
         Component: gst-plugins-base
        AssignedTo: gstreamer-bugs at lists.sourceforge.net
        ReportedBy: hadess at hadess.net
         QAContact: gstreamer-bugs at lists.sourceforge.net
     GNOME version: Unspecified
   GNOME milestone: Unspecified


See: https://bugzilla.redhat.com/show_bug.cgi?id=305501

alsa-lib sometimes gives us different answer to _get() when _set()'ing the
volumes quickly.

1. Launch gnome-volume-control
2. Check that the master track's channels are locked
3. Change the volume quickly, the 2 channels will become unlocked (the 2 tracks
end up with different volumes)

I debugged this in gst-plugins-base's gstalsamixer.c:
A quick succession of snd_mixer_selem_set_playback_volume and
snd_mixer_selem_get_playback_volume will result in 2 slightly different
results.

I add those lines in gst_alsa_mixer_get_volume():
      if (track->num_channels == 2 && volumes[0] != volumes[1])
             printf ("volumes[0]: %d volumes[1]: %d\n",
                    volumes[0], volumes[1]);
And saw this after dragging the sliders for a while:
volumes[0]: 31 volumes[1]: 21
etc.

The attached patch makes the set() use the _all() variants if all the tracks
are set to have the same volume.


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