[FFmpeg-trac] #3491(undetermined:new): MKV muxer corrupts subtitles

[FFmpeg]

#3491: MKV muxer corrupts subtitles
-------------------------------------+-------------------------------------
             Reporter:  ValdikSS     |                     Type:  defect
               Status:  new          |                 Priority:  important
            Component:               |                  Version:
  undetermined                       |  unspecified
             Keywords:               |               Blocked By:
             Blocking:               |  Reproduced by developer:  0
Analyzed by developer:  0            |
-------------------------------------+-------------------------------------
 Summary of the bug:
 Remuxing MKV with embedded subtitles can cause some sort of subtitles
 corruption in the resulting MKV file. Some lines or karaoke effects could
 disappear in certain video players.

 How to reproduce:
 I've uploaded 2 files into incoming folder on FTP: mkv_subtitles.mkv
 (http://yadi.sk/d/NM69ZxZQKzNn7) and mkv_subtitles_ffmpeg.mkv
 (http://yadi.sk/d/qDFmsDPQKzNoQ). The second one was remuxed with the
 following command:
 {{{
 ffmpeg -i mkv_subtitles.mkv -map 0 -map_metadata 0 -c copy
 mkv_subtitles_ffmpeg.mkv
 }}}
 Subtitles in the first file are played correctly while in ffmpeg-remuxed
 file some karaoke effects and english translation is missing (tested with
 cmplayer, vlc, mpv and mplayer. It works correctly only in mplayer).

 If you extract subtitles with
 {{{
 mkvextract tracks mkv_subtitles.mkv 1:sub_orig.ass
 mkvextract tracks mkv_subtitles_ffmpeg.mkv 1:sub_ffmpeg.ass
 }}}
 you can see the difference between them (with diff).

 But if you remux MKV with extracted subtitles (extracted either with
 ffmpeg or mkvextract, either from original or remuxed mkv with broken
 subtitles), it works fine.
 {{{
 ffmpeg -i mkv_subtitles.mkv -i sub_ffmpeg.ass -map 0 -map -0:s -map 1 -c
 copy test.mkv
 }}}

--
Ticket URL: <https://trac.ffmpeg.org/ticket/3491>
FFmpeg <https://ffmpeg.org>
FFmpeg issue tracker