Embedded ASS subtitle support

[SubJunk]

It would be great to see support for embedded ASS subtitles.
Currently ASS subtitles are only supported if there is an external .ass file, but almost always it is a stream inside an MKV container (so there are 3 streams: video, audio and ASS subtitle)

It is possible currently to extract the subtitle stream from the original container, then load it in a second step, but it would be cool to be able to do it in one step instead.

For example in MEncoder you use:
mencoder input.mkv -ass -o output.mkv
And it will burn the ASS/SSA subtitles contained within input.mkv onto the video stream of output.mkv

[SubJunk]

Ah I forgot to provide a sample. It's here:
​http://www.spirton.com/uploads/Unsorted/ffmpeg-1305-sample.mkv
It's a 4MB direct link on my server so it won't be going anywhere :)

[Cigaes]

That would be nice indeed, but that is hard.

Adding support for subtitles in libavfilter (and not as an external resource for a single filter) is a project, but it requires careful design, especially since, unlike video and audio streams, subtitles streams are sparse.

So yes, it will eventually be possible. But do not hold your breath yet.

[SubJunk]

6 months went by, is it any closer to being easier to develop this feature or is it a pipedream? :)

[Clément Bœsch]

Unfortunately, there are a lot of subtitle issues to solve before considering this; help is needed if you are interested...

Note that you can extract the ASS track from the MKV into an external ASS (ffmpeg -i in.mkv out.ass) so you can achieve the operation anyway, it just takes two steps instead of one.

[SubJunk]

OK, no problem. I'm happy to help in any way I can. I'm idling in #ffmpeg-devel if you want to chat there