[FFmpeg-devel] [PATCH] Lost VBR header

Nicolas George nicolas.george at normalesup.org
Sun Apr 17 17:33:24 CEST 2011

L'octidi 28 germinal, an CCXIX, Peter Belkner a écrit :
> For the moment I think it's best to leave it as it is and hear some
> other opinions.

IMHO, but I am not a specialist of the question at all:

- The demuxer should parse these VBR header frames if it makes sense, and
  discard them.

  This means we consider that these VBR header frames are part of the format
  and not of the payload. This is what Ogg does: the first packet(s) of a
  stream is parsed as the header for the stream. And we acknowledge that
  some broken software produce MP3 files with several, bogus VBR header

  A demuxer-specific option can be present to disable the discarding, but
  the default should be to disable.

- The muxer should generate a correct VBR header frame for the data that has
  just been written. Efforts should be made so that, when demuxing and
  remuxing the same data, _if the original file was 100% correct_, then the
  generated VBR frame is bit-identical to the original.

  Again, a muxer-specific option could allow to disable the generation of
  the VBR header frame.

- The decoder should be resilient to stray VBR header frames, since there
  are in the wide world files that are not in MP3 container format with such
  frames, and adding a special case to all demuxers is not an option.


  Nicolas George
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