[FFmpeg-trac] #3256(avformat:open): FFMPEG SVQ3 Matroska remux produces unplayable output (FFPlay don't want to play SVQ3 MKV output)

FFmpeg trac at avcodec.org
Sun Jan 19 09:13:45 CET 2014

#3256: FFMPEG SVQ3 Matroska remux produces unplayable output (FFPlay don't want to
play SVQ3 MKV output)
             Reporter:  Vika         |                    Owner:
  Apelsinova                         |                   Status:  open
                 Type:  defect       |                Component:  avformat
             Priority:  important    |               Resolution:
              Version:  git-master   |               Blocked By:
             Keywords:  mkv svq3     |  Reproduced by developer:  1
  regression                         |
             Blocking:               |
Analyzed by developer:  1            |

Comment (by Vika Apelsinova):

 The bug was fixed in MKVToolNix by
 but FFPlay and VLC still don't want to play output.
 > Not really, the output file was invalid (and can not be decoded with

 Moritz Bunkus a.k.a. mosu wrote:
 That VLC doesn't play audio doesn't mean that mkvmerge is to blame.
 Quite the other way around. VLC doesn't support A_QUICKTIME at all.
 Just do a recursive grep for A_QUICKTIME on VLC's sources and you'll
 see for yourself.

 As for the CodecID. mkvmerge has used A_QUICKTIME since 2009. Before
 it used A_QUICKTIME/QDMx. Back then there was a decision that
 appending the codec type to the A_QUICKTIME string was superfluous as
 the FourCC is contained in CodecPrivate for both A_QUICKTIME and
 A_QUICKTIME/QDMx. This is very similar to how V_QUICKTIME works. The
 CodecPrivate contains the content of the STSD atom.

 Unfortunately we totally forgot to update the specs page, which is why
 it doesn't list A_QUICKTIME. I will update the specs page tonight.

 So if you want to fix ffmpeg you should do the following:

 1. In the demuxing part: treat A_QUICKTIME and A_QUICKTIME/wxyz
 identically. Get the FourCC from CodecPrivate (should be bytes 4 - 7
 starting at 0).
 2. In the muxing part: simply don't write A_QUICKTIME/wxyz but just

Ticket URL: <https://trac.ffmpeg.org/ticket/3256#comment:6>
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