[FFmpeg-devel] [RFC] Yet another subtitles open question

[Clément Bœsch]

On Wed, Oct 02, 2013 at 12:10:38PM -0700, Josh Allmann wrote:
> On 1 October 2013 11:14, Clément Bœsch <u at pkh.me> wrote:
> > Hi folks,
> >
> > I have definitely better to do, and I still hate subtitles, but we need to
> > make some changes, and I'm willing to help.
> >
> > Shell
> > -----
> >
> > So here it is, I'd like to move on with the API. Currently we use
> > AVSubtitle (and its AVSubtitleRects) which is defined in lavc. We wanted
> > at some point to move it to libavutil, eventually with slight changes.
> > OTOH, the idea of using the AVFrame was disregarded quickly for various
> > reasons. The thing is, it might have various benefits:
> >
> >  - since it doesn't introduce a new struct and its own semantic, it will
> >    ease a lot its integration with for instance libavfilter, and probably
> >    allow various code refactoring
> >
> >  - AVFrames have a ref counting system: if audio and video are ref
> >    counted, we expect the subtitles to be as well, otherwise it can become
> >    a source of pain for users
> >
> >  - using AVFrame also suggest the idea that we could embed subtitles data
> >    within existing AVFrame: think closed captioning. "Freelance" subtitles
> >    OTOH would just use a empty/zero frame shell. Note that this conflicts
> >    with the ref counting idea since it can't share the data buffers.
> >
> > Opinion on this?
> >
> 
> In Libav we're thinking of introducing an opaque field into AVFrame
> for other purposes, and I'm thinking of leveraging it for
> subtitle-related things there.

Can you detail a bit more? I'm not sure I follow you with the opaque
field. It sounds like it will require the AVSubtitle to be moved to
libavutil anyway.

-- 
Clément B.
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