Cannot set dispositions for subtitle streams inside MKV other than Default and Forced
|Reported by:||droid-xx||Owned by:|
|Blocking:||Reproduced by developer:||no|
|Analyzed by developer:||no|
I'm not sure whether this is a bug or a feature but I'm filing this since the documentation on disposition types is lacking details.
If this is a feature, then there's probably some internal checking by ffmpeg to determine whether the disposition type given by the user can be applied to the selected stream. So obviously if you pass a disposition type of "attached_pic" to a subtitle it won't make any sense, hence nothing will change in the output disposition-wise (although there's no error or warning displayed to inform the user about this, and the documentation doesn't state which dispositions apply to which types of streams).
However there are at least 2 more dispositions that can be set for subtitle streams: "karaoke" (for ass/ssa which are designed as karaoke subtitles) and "hearing_impaired" (for SDH subtitles).
This works for the third subtitle track inside an .mkv with a total of 3 subtitle streams:
ffmpeg -i input.mkv -map 0 -c copy -disposition:s:2 forced output.mkv
This won't work (disposition is ignored with no errors/warnings):
ffmpeg -i input.mkv -map 0 -c copy -disposition:s:2 hearing_impaired output.mkv
ffmpeg -i input.mkv -map 0 -c copy -disposition:s:2 karaoke output.mkv