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• avcodec/utvideodec/enc : Fix edge case of creating Huffman table

  24 septembre 2020, par Andreas Rheinhardt

  avcodec/utvideodec/enc : Fix edge case of creating Huffman table
  The Ut Video format stores Huffman tables in its bitstream by coding
  
  the length of a given symbol ; it does not code the actual code directly,
  
  instead this is to be inferred by the rule that a symbol is to the left
  
  of every shorter symbol in the Huffman tree and that for symbols of the
  
  same length the symbol is descending from left to right. With one
  
  exception, this is also what our de- and encoder did.
  The exception only matters when there are codes of length 32, because
  
  in this case the first symbol of this length did not get the code 0,
  
  but 1 ; this is tantamount to pretending that there is a (nonexistent)
  
  leaf of length 32. This is simply false. The reference software agrees
  
  with this [1].
  [1] : https://github.com/umezawatakeshi/utvideo/blob/2700a471a78402e5c340150b38e8a793ef3676f1/utv_core/HuffmanCode.cpp#L280
  Reviewed-by : Paul B Mahol <onemda@gmail.com>
  
  Signed-off-by : Andreas Rheinhardt <andreas.rheinhardt@gmail.com>
  

  • [DH] libavcodec/utvideodec.c
  • [DH] libavcodec/utvideoenc.c

• avformat/matroskaenc : Fix edge case of writing Cues at the beginning

  28 décembre 2019, par Andreas Rheinhardt

  avformat/matroskaenc : Fix edge case of writing Cues at the beginning
  The Matroska muxer has the ability to write the Cues (the index) at the
  
  beginning of the file (in front of the Cluster) : The user inputs the
  
  amount of space that should be reserved at the beginning of the file and
  
  if this is sufficient, the Cues will be written there and the part of the
  
  reserved space not used up by the Cues will be filled with a "Void"
  
  element.
  There is just one problem with this : One can not fill a single byte this
  
  way, because said Void element is minimally two bytes long (one byte ID,
  
  one byte length field). Up until now, if one reserved one byte more than
  
  needed, one would run into an assert when writing the Void element.
  There are two solutions for this : Error out if it happens. Or adjust the
  
  length field of the Cues in order to ensure that the above situation
  
  can't happen (i.e. write the length on one byte more than necessary).
  
  The first solution is very unsatisfactory, as enough space has been
  
  reserved. Therefore this commit implements the second solution.
  Signed-off-by : Andreas Rheinhardt <andreas.rheinhardt@gmail.com>
  

  • [DH] libavformat/matroskaenc.c

• avcodec/agm : Do not allow MVs out of the picture area as no edge is allocated

  2 novembre 2019, par Michael Niedermayer

  avcodec/agm : Do not allow MVs out of the picture area as no edge is allocated
  Fixes : out of array access
  
  Fixes : 18499/clusterfuzz-testcase-minimized-ffmpeg_AV_CODEC_ID_AGM_fuzzer-5749038406434816
  Found-by : continuous fuzzing process https://github.com/google/oss-fuzz/tree/master/projects/ffmpeg
  
  Signed-off-by : Michael Niedermayer <michael@niedermayer.cc>
  

  • [DH] libavcodec/agm.c