[FFmpeg-trac] #9105(ffmpeg:new): Cannot set dispositions for subtitle streams inside MKV other than Default and Forced

FFmpeg trac at avcodec.org
Wed Feb 17 12:44:45 EET 2021


#9105: Cannot set dispositions for subtitle streams inside MKV other than Default
and Forced
-------------------------------------+-------------------------------------
             Reporter:  droid-xx     |                    Owner:
                 Type:  defect       |                   Status:  new
             Priority:  normal       |                Component:  ffmpeg
              Version:  unspecified  |               Resolution:
             Keywords:  ffmpeg       |               Blocked By:
  disposition metadata               |
             Blocking:               |  Reproduced by developer:  0
Analyzed by developer:  0            |
-------------------------------------+-------------------------------------

Comment (by mkver):

 There are no internal checks whether a disposition can be applied at all;
 instead most muxers just don't check the disposition at all, because the
 format either does have anything that one can map these dispositions to or
 because doing so is just unimplemented. And if a muxer supports a specific
 disposition flag, it only checks for whether this flag is set or not and
 ignores all the others.

 The Matroska muxer is one of the few muxers that preserve some
 dispositions. But it can only preserve those dispositions for which there
 is a matching Matroska element. This is not so for karaoke and up until
 [https://github.com/ietf-wg-cellar/matroska-
 specification/commit/0e330fded85654d637c256797ea9cc6bfb79fde3 very
 recently] it was also not true for hearing_impaired. I have just sent a
 [https://ffmpeg.org/pipermail/ffmpeg-devel/2021-February/276322.html
 patchset] that implements support for hearing_impaired and a few other
 dispositions that Matroska now supports.

 Matroska always allowed to preserve the attached_pic disposition (for
 video streams only); it is just unimplemented. I need to finally
 [https://github.com/mkver/FFmpeg/commit/f7f5ae9e4b65b7adcdffc63e915c47509088a6ea
 finish this].

--
Ticket URL: <https://trac.ffmpeg.org/ticket/9105#comment:2>
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