[gstreamer-bugs] [Bug 526173] [typefinding] fails to detect mpeg video stream whereas mplayer plays it properly

[GStreamer (bugzilla.gnome.org)]

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  GStreamer | gst-plugins-base | Ver: HEAD CVS

Tim-Philipp Müller changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
 Attachment #108612|none                        |rejected
               Flag|                            |
             Status|NEEDINFO                    |RESOLVED
         Resolution|                            |FIXED
            Summary|typefind fail to detect mpeg|[typefinding] fails to
                   |stream whereas mplayer plays|detect mpeg video stream
                   |it properly                 |whereas mplayer plays it
                   |                            |properly
   Target Milestone|HEAD                        |0.10.20




------- Comment #5 from Tim-Philipp Müller  2008-04-30 21:01 UTC -------
This should fix it:

 2008-04-30  Tim-Philipp Müller  <tim.muller at collabora co uk>

        * gst/typefind/gsttypefindfunctions.c:
          (mpeg_video_stream_ctx_ensure_data), (mpeg_video_stream_type_find),
          (plugin_init):
          Rework mpeg video stream typefinding a bit more: make sure sequence,
          GOP, picture and slice headers appear in the order they should and
          that we've in fact at least had one of each; fix picture header
          detection; decouple picture and slice header check - don't assume
          they're at a fixed offset, there may be extra data in between. Also,
          announce varying degrees of probability depending on what we found
          exactly (multiple pictures, at least one picture, just sequence and
          GOP headers). Finally, in _ensure_data(), take into account that we
          might be typefinding smaller amounts of data, such as the first
          buffer of a stream, so fall back to the minimum size needed as long
          as that's available, instead of erroring out if there's less than
          2kB of data. Fixes #526173. Conveniently also doesn't recognise the
          fuzzed file from #399342 as valid.

The function your patching shouldn't really be needed at all (I've removed it
now), mpeg_video_stream_type_find() should pick it up.

But even if not, your patch isn't really ideal, since it calls
gst_typefind_peek() not less than a hundred thousand something times (!) in the
worst case, e.g. if this is not an mpeg video stream and there wasn't random
data that happens to look like a sequence header and no other typefinder
short-circuited the typefinding process with a PRIMARY probability.

Please re-open if this doesn't fix it for the full file. Thanks!


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