[FFmpeg-devel] Internal handling of subtitles in ffmpeg

Reimar Döffinger Reimar.Doeffinger
Fri Dec 19 12:57:19 CET 2008

On Fri, Dec 19, 2008 at 12:20:46PM +0100, Michael Niedermayer wrote:
> the subtitle decoders are supposed to output what is stored in the bitstream
> in a decompressed and generic repressentation.

I am arguing that this generic representation is bitmap format also for

> this repressentation can contain bitmaps as well as pieces of text,
> a subtitle decoder outputs a AVSubtitle which contains several AVSubtitleRect
> each of these could be a bitmap, or text (text isnt supported yet).

What would be the advantage of allowing text in AVSubtitleRect? Well, I
can think of a few, bug I think it will be a really huge, giant,
incredibly complex mess to support ASS that way.
I let myself happily be proven wrong, but I don't want a format that
barely works for some text formats but has no chance of ever supporting
extended text stuff.

> If a ASS supports bitmaps in addition to text this would not even need a
> change to what i suggested. The output of our subtitle
> decoders IS vector based and always was, there is no issue with mixing
> text and graphics.

The way you suggest there is no issue with mixing them, but I see an
issue with representing styled text.
Also I had thought the idea was to have two basic formats: ASS for text
subtitles, bitmaps for others. As I see it, you are suggesting
a third one that seems like a mixture of those? I would have been
in favour of just a way to convert between those two.

Reimar D?ffinger

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