[FFmpeg-devel] [RFC] Talk about subtitles

Reimar Döffinger Reimar.Doeffinger at gmx.de
Sat Nov 26 11:19:24 CET 2011

On Fri, Nov 25, 2011 at 07:48:42PM +0100, Reimar Döffinger wrote:
> On Thu, Nov 24, 2011 at 02:24:13AM +0100, Clément Bœsch wrote:
> >  - hardsub: I would see a -vf subtitles=f=inputsub.srt:... just like the
> >    proposed vf_ass. That filter would actually decode any kind of
> >    subtitles (SRT included) and burn them with the appropriate settings.
> >    To decode the subtitles and get the bitmap it would use libass, but
> >    through the API.
> Unless it is a source filter a filter has no business messing with files
> directly. And I don't see why you should need or want any other filter
> than src_movie, which already will have to handle subtitles anyway.
> You then have AVSubtitle structs you can pass around - and they will
> only have one of bitmap, ASS or plaintext - having a whole library
> just for converting between those seems a bit like overkill.
> By making the reading, decoding and hardsubbing a single filter you
> destroy any possibility of doing any kind of processing without having
> to implement it twice, once for soft- and once for hardsub.
> E.g. adjusting the aspect of the subs, delaying it, adjusting
> contrast/brightness, coloring them, ...

Note that while better than nothing the vf_ass filter is even worse:
it does not only not support embedded subs and other (strange?) things,
but it can't even read the subtitle over http, ftp or whatever else.

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