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• Are the av_free* functions in ffmpeg idempotent ?

  19 mars 2014, par Dan Hook

  Specifically I'm looking at avformat_free_context. In normal execution of my code, avformat_free_context is called appropriately. I would also like to call it in the destructor of a class, in case there was an exceptional case that caused the code using the AVFormatContext to return early. Do the ffmpeg free functions behave appropriately when called on already freed data structures ?

• mov : Disable advanced_editlist for fragmented MP4 input

  28 décembre 2022, par Derek Buitenhuis

  mov : Disable advanced_editlist for fragmented MP4 input
  Advanced edit list support is entirely broken for fragmented MP4s,
  
  currently. mov_fix_index is never run in mov_build_index, since
  
  in fragmented MP4s the stco, stsz, stts, and stsc boxes have zero
  
  entries, with the index being filled in as each fragment's trun
  
  box is seen.
  The result of this is that the skip samples is never set properly,
  
  since half the code thinks it doesn't need to, as advanced_editlist
  
  is enabled, but as mov_fix_index is never called, it doesnt get set.
  
  This means that any edits for e.g. priming are not properly applied
  
  as skip samples side data.
  This also means remuxing to fragmented MP4 from progressive MP4 with
  
  lavf will quietly drop the edit list, currently.
  Example :
      $ ffmpeg -loglevel quiet -advanced_editlist 1 -i non_fragmented.mp4 -f md5 -
  
      MD5=d02d929f8eb4edef624758a298d5f7c6
  
      $ ffmpeg -loglevel quiet -advanced_editlist 0 -i non_fragmented.mp4 -f md5 -
  
      MD5=d02d929f8eb4edef624758a298d5f7c6
  
      $ ffmpeg -loglevel quiet -advanced_editlist 1 -i fragmented.mp4 -f md5 -
  
      MD5=e38b110f586fa886ff94e0ca98a95d59 <— wrong, extra samples are output instead of being skipped
  
      $ ffmpeg -loglevel quiet -advanced_editlist 0 -i fragmented.mp4 -f md5 -
  
      MD5=d02d929f8eb4edef624758a298d5f7c6
  We cannot call mov_fix_index after reading a trun box
  
  since mov_fix_index seems to assume it is only called once, on a
  
  fully complete index, an multiple calls to it don't seem like
  
  they'd work, so the "best" option seems to be disabling advanced
  
  edit list support entirely for the time being, as it is broken
  
  for these types of files.
  Signed-off-by : Derek Buitenhuis <derek.buitenhuis@gmail.com>
  

  • [DH] libavformat/mov.c

• avcodec/utils : split side-data in new decode API too

  28 avril 2016, par wm4

  avcodec/utils : split side-data in new decode API too
  The deprecated avcodec_decode_video2() and avcodec_decode_audio4()
  
  functions called av_packet_split_side_data() on the input packets. This
  
  is required for packets produced by libavformat with the
  
  AVFMT_FLAG_KEEP_SIDE_DATA flag unset (which is unfortunately the
  
  default).
  The new API didn’t do this yet, although it didn’t matter as no decoder
  
  supports the new API yet. The emulation layer for the old API calls the
  
  old API functions, which took care of the splitting. Add this code to
  
  the new API codec entrypoints too, because we shouldn’t send essentially
  
  corrupted data to decoders.
  

  • [DH] libavcodec/utils.c