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

Michael Niedermayer michaelni at gmx.at
Wed Oct 2 22:03:25 CEST 2013

Hi Josh

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.

I would suggest that you base your subtitle work on ffmpeg, ubitux,
nicolas and others have put quite some time into it and if all
developers interrested in subtitles work together both projects would
move farther and faster forward in respect to subtitles.
randonmly rebasing commits from ffmpeg or redoing (and then having to
retest, redebug, refix, ...) is a really silly thing ...

Michael     GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB

Dictatorship naturally arises out of democracy, and the most aggravated
form of tyranny and slavery out of the most extreme liberty. -- Plato
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