[FFmpeg-devel] [RFC] XSUB subtitle decoder

Michael Niedermayer michaelni
Sun Aug 5 13:21:22 CEST 2007


On Sat, Aug 04, 2007 at 08:55:20PM +0200, Reimar D?ffinger wrote:
> Hello,
> here is my first approach it this, unfortunately there are a lot of
> problems.
> 1) I have only one very short sample:
>   http://samples.mplayerhq.hu/sub/small.divx
>   The other sample on our server:
>   http://samples.mplayerhq.hu/sub/DivX+Subtitles.divx
>   I am fairly certain that this does not contain any subtitles at all
>   (though it contains a subtitle stream).
> 2) ffplay is the only application to test, but unfortunately seems to be
>    quite buggy:
>    It does not check the boundaries if the subtitle before drawing
>    it, so the small sample above crashes it since the y-Koordinate is
>    too big. The reason for this is I think, that xsub gives
>    Koordinates as on the DVD, i.e. assuming PAL resolution while
>    ffplay assumes they are actual coordinates.
>    The decoder can not do this transformation though since currently
>    the actual movie resolution is not provided to it.

hmm, whats in AVCodecContext.width/height? it seems these get read from
avi for the subtitle stream?

> 3) The start_display_time and end_display_time are relative to the
>    packet pts. I lack a large enough sample to know if this works for
>    xsub, but for the general case it seems like quite a strong
>    assumption. Since packet pts is not passed to the decode function,
>    a conversion is not possible here either.

if relative doesnt work for some subtitle codec, we will have to think
about what to do ...
maybs simply adding a absolute_ts flag to AVCodec would do but maybe there
are better solutions ...

patch looks ok ...

Michael     GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB

No great genius has ever existed without some touch of madness. -- Aristotle
-------------- next part --------------
A non-text attachment was scrubbed...
Name: not available
Type: application/pgp-signature
Size: 189 bytes
Desc: Digital signature
URL: <http://lists.mplayerhq.hu/pipermail/ffmpeg-devel/attachments/20070805/f3c95db6/attachment.pgp>

More information about the ffmpeg-devel mailing list