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• avformat/asfdec_o : Don't segfault with lots of attached pics

  12 novembre 2020, par Andreas Rheinhardt

  avformat/asfdec_o : Don't segfault with lots of attached pics
  The ASF file format has a limit of 127 streams and the "asf_o" demuxer
  
  (the ASF demuxer from Libav) has an array of pointers for a structure
  
  called ASFStream that is allocated on demand for every stream. Attached
  
  pictures are not streams in the sense of the ASF specification, yet the
  
  demuxer created an ASFStream for them ; and in one codepath it also
  
  forgot to check whether the array of ASFStreams is already full. The
  
  result is a write beyond the end of the array and a segfault lateron.
  Fixing this is easy : Don't create ASFStreams for attached picture
  
  streams.
  (Other results of the current state of affairs are unnecessary allocations
  
  (of ASFStreams structures), the misparsing of valid files (there might not
  
  be enough ASFStreams left for the valid streams if attached pictures take
  
  up too many) ; furthermore, the ASFStreams created for attached pictures all
  
  have the stream number 0, an invalid stream number (the valid range is
  
  1-127). This means that invalid data (packets for a stream with stream
  
  number 0) won't get rejected lateron.)
  Signed-off-by : Andreas Rheinhardt <andreas.rheinhardt@gmail.com>
  

  • [DH] libavformat/asfdec_o.c

• avcodec/mpeg12dec : Don't adapt (last|next)_pic.linesize for field pics

  23 juin 2024, par Andreas Rheinhardt

  avcodec/mpeg12dec : Don't adapt (last|next)_pic.linesize for field pics
  These values are not read anywhere. Furthermore, since commit
  
  fe6037fd04db8837dcdb9013f9c4ad4e7eb0592e the linesize values
  
  of the MPVWorkPictures were wrong for subsequent fields
  
  in a chain of B-pictures (as they are always doubled and no longer
  
  based upon the frame-linesizes) which can eventually lead to overflow.
  Finally, it makes no real sense to ever double the linesize
  
  of the reference pictures at all : Even when the current picture
  
  is a field, it can still reference both fields of reference
  
  pictures and therefore the linesize should allow to address
  
  both fields (for the same reason, data is not offset for
  
  reference pictures).
  libavcodec/mpeg12dec.c:1304:41 : runtime error : signed integer overflow : 4611686018427387904 * 2 cannot be represented in type 'long'
  issue : 69732/clusterfuzz-testcase-minimized-ffmpeg_AV_CODEC_ID_MPEGVIDEO_fuzzer-5123551179374592
  Reviewed-by : Michael Niedermayer <michael@niedermayer.cc>
  
  Signed-off-by : Andreas Rheinhardt <andreas.rheinhardt@outlook.com>
  

  • [DH] libavcodec/mpeg12dec.c

• ffmpeg.concat too slow when trying to merge video and audio file

  9 août 2021, par Geo

  I've been merging video and audio files with FFmpeg successfully but it's really slow. But I wanted to know if there's any way to speed this up, I'm really new to this module and I don't understand most stuff about it and how it works

  


  here's an example code :

  


  import ffmpeg


video = ffmpeg.input( 'C:/Users/geo/Downloads/video.mp4')
audio = ffmpeg.input ('C:/Users/geo/Downloads/audio.mp4')


ffmpeg.concat(video, audio, v = 1, a = 1).output('C:/Users/geo/Downloads/merged.mp4').run()


  


  thanks in advance