[FFmpeg-devel] DVD subtitles

Wolfram Gloger wmglo
Thu Feb 28 22:29:56 CET 2008

> From: Vitor Sessak <vitor1001 at gmail.com>
> Erik Slagter wrote:
> > Ehmmm, afaik subtitles are pixel-format internally in libav*. If not, 
> > there would really be a problem using DVD subtitles.
> Are you sure? I'd say it is more as a codec as any other, but not a 
> pixel format... Anyway, I have never touched the subtitle code, so maybe 
> you know better...

Yes, subtitles are definitely stored as pixels in AVSubtitle, so a
"capitalization" filter would be really hard.  I believe AVSubtitle
was designed closely modelling DVB subtitles.

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).

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..


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