[gstreamer-bugs] [Bug 579692] New: mp3_type_find is over-optimistic

[GStreamer (bugzilla.gnome.org)]

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  GStreamer | gst-plugins-base | Ver: 0.10.21
           Summary: mp3_type_find is over-optimistic
           Product: GStreamer
           Version: 0.10.21
          Platform: Other
        OS/Version: All
            Status: UNCONFIRMED
          Severity: normal
          Priority: Normal
         Component: gst-plugins-base
        AssignedTo: gstreamer-bugs at lists.sourceforge.net
        ReportedBy: arnout at mind.be
         QAContact: gstreamer-bugs at lists.sourceforge.net
     GNOME version: Unspecified
   GNOME milestone: Unspecified


Typefind may identify an H.264 stream as an MPEG-1 audio stream (with a low
probability) when it has not yet received sufficient data to identify it as an
H.264 stream.

I'll attach a sample stream.  With

gst-launch -v filesrc location=foo.h264 ! typefind ! fakesink silent=true

it finds caps = video/x-h264

With

gst-launch -v filesrc location=foo.h264 ! queue ! typefind ! fakesink
silent=true

it finds caps = audio/mpeg, mpegversion=(int)1, layer=(int)1

The queue makes typefind operate in push mode, so it is (initially) limited to
the first 4096 bytes, which don't contain sufficient H.264 slice headers yet to
identify it.  mp3_type_find sets the probability at 20 so it wins.

I haven't tried with git head but (looking at the diffs of typefindfunctions.c)
don't see how it would make a difference.

Proposed patch will follow


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