[FFmpeg-trac] #2035(undetermined:new): DVD subtitle from VOB does not contain CodecPrivate data

FFmpeg trac at avcodec.org
Sun Dec 16 17:23:48 CET 2012

#2035: DVD subtitle from VOB does not contain CodecPrivate data
             Reporter:  billie       |                     Type:  defect
               Status:  new          |                 Priority:  normal
            Component:               |                  Version:  git-
  undetermined                       |  master
             Keywords:               |               Blocked By:
             Blocking:               |  Reproduced by developer:  0
Analyzed by developer:  0            |
 Summary of the bug:

 When copying DVD subtitles from vob files into the matroska container the
 subtitles do not contain CodecPrivate data.

 The subtitles play fine in vlc but mkvtoolnix has problems with editing
 the file. The header editor recognizes all tracks but mkvextract fails to
 extract the subtitles because of the missing data (Error: Track 5 with the
 CodecID 'S_VOBSUB' is missing the "codec private" element and cannot be
 extracted.). Also editing the file with mmg/mkvmerge does not work because
 the existing subtitles are ignored and not written to the output file
 because of the same reason (Warning: matroska_reader: The CodecID for
 track 5 is 'S_VOBSUB', but there was no private data found).

 While I understand that the CodecPrivate data is not direct available when
 reading from VOB files as this information normally comes from the IDX
 part of extracted subtitles in vobsub format. However it would be nice if
 this information could be acquired somehow and written to the codec
 initialization part for the files to be editable by mkvtoolnix. This would
 save the additional step of extracting the subtitles to IDX/SUB. I guess
 that the ultimate solution would be to add a DVD reader who understands
 the dvd structure as I this information is stored in the IFO file.

 How to reproduce:
 % ffmpeg -i concat:VTS_01_1.VOB\|VTS_01_2.VOB\|VTS_01_3.VOB\|VTS_01_4.VOB
 -map 0:0 -map 0:1 -map 0:2 -map 0:6 -map 0:5 -map 0:4 \
 -c:v libx264 -preset fast -crf 18 \
 -c:a copy -metadata:s:a:0 language=ger \
 -c:a copy -metadata:s:a:1 language=eng \
 -c:s copy -metadata:s:s:0 language=eng \
 -c:s copy -metadata:s:s:1 language=ger \
 -c:s copy -metadata:s:s:2 language=ger \
 -f matroska movie.mkv

 ffmpeg version N-47903-gde89dff
 built on Dec 16 2012 15:51:01

Ticket URL: <https://ffmpeg.org/trac/ffmpeg/ticket/2035>
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