[FFmpeg-devel] DVD subtitles

Erik Slagter erik
Fri Feb 29 10:22:53 CET 2008

Wolfram Gloger wrote:

> I have recently restarted on DVD subtitle _en_coding and had to create
> two "filters", one merging several AVSubtitleRect's into a single
> bigger one, and one for colormap compression (DVD subtitles have only
> 4 colors out of a palette of 16).

Ah, at least 1 person more with interest in DVD subtitles :-) And yeah, 
the way subtitles are implemented on DVD's (and other things as well) 
really sucks, but I guess that's the way of the world ;-)

What exactly can I do with subtitles using the ffmpeg program before and 
after your contribution? I was under the impression that it was already 
possible to convert dvb subtitles from and to dvb subtitles. Otherwise, 
I wouldn't really get the usefulness of subtitle support in ffmpeg.

> Now looking at making this more general, I wonder why AVSubtitleRect
> wasn't derived from AVPicture (with PixelFormat PIX_FMT_PAL8).
> Then the filter infrastructure could probably be used without
> any special casing..

I guess the SubtitleRects can have varying bounds and offsets as opposed 
to a picture?

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