[FFmpeg-devel] [PATCH] Matroska demuxer adds WebVTT support

wm4 nfxjfg at googlemail.com
Fri Jul 19 21:40:40 CEST 2013

On Fri, 19 Jul 2013 20:01:26 +0200
Nicolas George <nicolas.george at normalesup.org> wrote:

> Le primidi 1er thermidor, an CCXXI, wm4 a écrit :
> > To be fair, it's exactly the same for ASS subtitles. FFmpeg now has two
> > packet formats for ASS: one as used in Matroska packets ("ass"), and one
> > as used in .ass files ("ssa", has nothing to do with SSA). This is a
> > recent change, and before this, matroskadec.c mangled the Matroska
> > packets to make them look like the packets assdec.c outputs. But this
> > was a problem in some ways (for example, duplicated timestamps), so it
> > was changed.
> > 
> > In my opinion, the Matroska ASS packet format is a superset of what
> > assdec.c outputs, so assdec.c should be changed to output the Matroska
> > format.
> That is the plan. The packet format for the SSA codec id was a quick hack to
> get the interface with libass working, but it was very badly designed from
> an API point of view.
> The plan is to deprecate the SSA codec id in favour of ASS, both for the
> Matroska muxer and demuxer (done), the .ass text file muxer (done) and the
> .ass text file demuxer (not yet done, should be easy).

What about "decoded" subtitles? They use the "ssa" format as well.

> The ultimate goal would be that ffprobe -show_data shows the same thing when
> reading from a .ass file or from a Matroska file produced by a third-party
> application (mkvmerge), and also the same thing as visible in a hex dump of
> the Matroska file directly.
> Regards,

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