[NUT-devel] [RFC] subtitle fourccs

Michael Niedermayer michaelni at gmx.at
Mon Mar 3 03:30:49 CET 2008

On Sun, Mar 02, 2008 at 11:33:47PM +0000, Måns Rullgård wrote:
> Michael Niedermayer <michaelni at gmx.at> writes:
> > Hi
> >
> > We need a list of fourcc <-> subtitle codecs for nut.
> > Any tips where i can find one? (yes i tried google)
> If you want to reuse values from another container, maybe MOV has
> something.  

our mov demuxer only has:
const AVCodecTag ff_codec_movsubtitle_tags[] = {
    { CODEC_ID_MOV_TEXT, MKTAG('t', 'e', 'x', 't') },
    { CODEC_ID_MOV_TEXT, MKTAG('t', 'x', '3', 'g') },
    { CODEC_ID_NONE, 0 },
(the rest has to be detected by other messy ways ...)

and the spec says:
"The data format field in the sample description is always set to 'text'."

so i dont see how this could be used ...

> AVI doesn't support subtitles, so that can't be used as a
> reference here (and I still think using AVI as a model for anything is
> utterly stupid).

Ironically avi is pretty much the only container with simple and working
codec identification. In .mp4 we couldnt even agree which value identifies
the codec :)
mpeg-ps/ts has a dozen identifiers and tables but all of them together
are insufficient to distingish h.264 from mpeg2 in practice.
ogg leaves codec identification to the codec (aka it has no codec
Whats left is mov (which is kinda similar to avi) and dozens of formats
which only support a single codec thus dont need a identification system.
And of course matroska which has a dozen different id systems.


Michael     GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB

Those who are too smart to engage in politics are punished by being
governed by those who are dumber. -- Plato 
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