[FFmpeg-devel] Rendering text-based subtitles

Stefano Sabatini stefano.sabatini-lala at poste.it
Sun May 29 16:00:20 CEST 2011

On date Sunday 2011-05-29 15:50:50 +0200, Nicolas George encoded:
> L'octidi 8 prairial, an CCXIX, Chris Burel a écrit :
> > Where does the rendering code really belong?  In the ass decoder?  In the
> > ass encoder?  Somewhere else entirely?
> IMHO, the most logical place would be libavfilter:
> - one filter convert text subtitles to bitmap subtitles;
> - one filter to forcefully compose overlapping bitmap subtitles;
> - one filter to overlay bitmap subtitles on top of a video.
> Currently, AFAIK, libavfilter has no support for subtitles filters, but it
> does not seem very hard to add. Adding support for subtitles filters to the
> ffmpeg command line tool would probably require a little more work.
> Unfortunately, I fear that adding support for mixed subtitles+video filters
> to the command line tool would be much harder.

In the final design we'll have a single multimedia graph, while we
currently have different filterchains for each specific media, audio
is still a work in progress, unifying A/V/S path in the ff* tools
doesn't look trivial.

Starting by adding support to subtitles/text in libavfilter (and while
at it improve subtitles support in libavcodec) would be definitively
very welcome.
FFmpeg = Foolish Frenzy Merciless Peaceful Eager Genius

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