[gstreamer-bugs] [Bug 433245] New: Non-mutex-protected calls to avcodec_open/_close

[GStreamer (bugzilla.gnome.org)]

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  GStreamer | gst-ffmpeg | Ver: HEAD CVS
           Summary: Non-mutex-protected calls to avcodec_open/_close
           Product: GStreamer
           Version: HEAD CVS
          Platform: Other
        OS/Version: Linux
            Status: UNCONFIRMED
          Severity: normal
          Priority: Normal
         Component: gst-ffmpeg
        AssignedTo: gstreamer-bugs at lists.sourceforge.net
        ReportedBy: bilboed at bilboed.com
         QAContact: gstreamer-bugs at lists.sourceforge.net
     GNOME version: Unspecified
   GNOME milestone: Unspecified


We have mutexes to protect our explicit calls to avcodec_open/_close in
gst-ffmpeg since it's not thread-safe.

The problem is that some code in ffmpeg does call avcodec_open/_close, so we
need to protect some other ffmpeg calls with the same mutex.

* libavformat/utils.c . avcodec_open() is called in try_to_decode_frame() which
is called by av_find_stream_info(). avcodec_close() is also called in
av_find_stream_info(). Therefore any calls to av_find_stream_info() should be
protected by the avcodec_open/_close mutex.

* libavformat/jpeg.c . avcodec_open() is called in the read function. BUT
considering that we don't use the jpeg "demuxer", we don't need to do anything.

* libavcodec/mpegvideo.c . This is a tricky one. Called in
estimate_best_b_count(), which is called in select_input_picture() IF the
b_frame_strategy == 2, which is called in MPV_encode_picture(), which is the
encoding entry point for mpeg video encoders... BUT AFAIK, we don't modify
b_frame_strategy in gst-ffmpeg encoders, so it's always 0, and therefore the
call to avcodec_open/close is never done.


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