[Bug 781929] New: audioringbuffer: mpegaudioversion 3 (MP3 2.5) is refused

[GStreamer (GNOME Bugzilla)]

https://bugzilla.gnome.org/show_bug.cgi?id=781929

            Bug ID: 781929
           Summary: audioringbuffer: mpegaudioversion 3 (MP3 2.5) is
                    refused
    Classification: Platform
           Product: GStreamer
           Version: 1.11.2
                OS: Linux
            Status: NEW
          Severity: normal
          Priority: Normal
         Component: gst-plugins-base
          Assignee: gstreamer-bugs at lists.freedesktop.org
          Reporter: nicolas at ndufresne.ca
        QA Contact: gstreamer-bugs at lists.freedesktop.org
     GNOME version: ---

First, my apologies if there is some mistake in this report, I'm not very
knowledgeable in MPEG audio version. What I understood is that mpegaudioparse
will parse mpeg audio 1, layer 1 / 3. Additionally, it parses the 3 generations
of MP3. Those a commonly named as 1, 2 and 2.5, which we map into
mpegaudioversion as 1, 2 and 3.

First issue I found, is that mpegaudioversion 3 is rejected by the
audioringbuffer. Now, on wikipedia this is considered non-standard, but it's
widely used to transport human voice, as it reduces the bitrate. I think we
enable support for this in the audioringbuffer, sinks can still control their
template caps.

Second issue, while the code in mpegaudioparse can produce 1, 2 and 3, the
template advertise only 1 and 3.

Third issue, lame and mpegaudioparse disagree. An example:

gst-launch-1.0 -v audiotestsrc ! audio/x-raw,rate=8000 ! lamemp3enc  !
mpegaudioparse ! fakesink

8kHz is only supported for generation 2.5, lame report mpgeaudioversion=2,
mpegaudioparse will report 3 correctly. (maybe this should be filed seperatly
?)

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