[gstreamer-bugs] [Bug 476370] New: [faad] shouldn't set channel-positions for mono and stereo

[GStreamer (bugzilla.gnome.org)]

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  GStreamer | gst-plugins-bad | Ver: HEAD CVS
           Summary: [faad] shouldn't set channel-positions for mono and
                    stereo
           Product: GStreamer
           Version: HEAD CVS
          Platform: Other
        OS/Version: Linux
            Status: UNCONFIRMED
          Severity: normal
          Priority: Normal
         Component: gst-plugins-bad
        AssignedTo: gstreamer-bugs at lists.sourceforge.net
        ReportedBy: notverysmart at gmail.com
         QAContact: gstreamer-bugs at lists.sourceforge.net
     GNOME version: Unspecified
   GNOME milestone: Unspecified


faad always sets channel-positions on its caps, when nothing else does for the
common mono and stereo cases.  When used in a pipeline containing an adder,
this can lead to stuttering or skipping playback and other weirdness.

This gst-launch commandline (which is fairly similar in effect to the rhythmbox
crossfading player pipeline) demonstrates the problem:

ADDER_CAPS=audio/x-raw-int,rate=44100,channels=2,width=16,depth=16,signed=true,endianness=1234

gst-launch-0.10 \
  adder name=a ! $ADDER_CAPS ! volume ! audioconvert ! audioresample ! queue !
tee ! queue ! audioconvert ! alsasink \
  \
  audiotestsrc wave=4 ! audioconvert ! $ADDER_CAPS ! a. \
  \
  filesrc location=file.m4a ! decodebin ! audioconvert ! audioresample !
$ADDER_CAPS ! queue ! volume ! a.

The section of the pipeline after the adder appears needlessly complex here,
but it's there to allow us to plug in filters and additional sinks at runtime.

If you run that with -v, you can see that the caps of the elements downstream
from the adder alternate between having channel-positions and not.  The exact
effect of this on the output depends on the elements in that branch.  Sometimes
it plays continuously but skips sections of the stream, sometimes it plays
fragments with seconds of silence between them.


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