[FFmpeg-devel] Internal handling of subtitles in ffmpeg

Michael Niedermayer michaelni
Fri Dec 19 13:41:13 CET 2008

On Fri, Dec 19, 2008 at 01:20:02PM +0100, Michael Niedermayer wrote:
> On Fri, Dec 19, 2008 at 12:57:19PM +0100, Reimar D?ffinger wrote:
> > On Fri, Dec 19, 2008 at 12:20:46PM +0100, Michael Niedermayer wrote:
> > 
> > > 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,
> ffmpeg is supposed to be able to convert files, that wouldnt work when
> text is converted to bitmaps, unless you propose encoders do OCR ...

a few more points
text to speech (possibly for the vissually impaird)
easy to edit (fix typos, ...)
allows font, font size and other parameters to be changed, something
you surely would loose otherwise at least after converting it once by
text can be rendered at any size, upscaling bitmaps will end with
blurry staircase and or loss of sharp corners.
converting to bitmaps in every convertion of ffmpeg would make the
files huge as bitmaps are much larger than text.

for ffmpeg as a converter, pure bitmap subtitle support is not practical.

Michael     GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB

I hate to see young programmers poisoned by the kind of thinking
Ulrich Drepper puts forward since it is simply too narrow -- Roman Shaposhnik
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