[FFmpeg-devel] [PATCH] Decode codec private in mkv demuxer

[Aurelien Jacobs]

Evgeniy Stepanov wrote:

> On Friday 20 June 2008 00:02:41 Aurelien Jacobs wrote:
> > Evgeniy Stepanov wrote:
> > > Hi,
> > >
> > > codec private data of a Matroska track can require decoding, depending on
> > > the value of ContentEncodingScope element. The current mkv demuxer only
> > > decodes frame contents, but not private data.
> >
> > OK. Now, can you provide some samples requiring extradata decoding ?
> > What tool can generate them ?
> 
> You can get a sample here: http://rut.org/mplayer/
> Mkvinfo shows "Haali DirectShow Matroska Muxer 1.8.122.18" as muxing 
> application.
> 
> > > The first patch moves buffer decoding code to a separate function. The
> > > second patch uses it to decode track private data.
> >
> > Patches are mostly good, but may benefit from some improvements.
> > For example, I think that COMP_HEADERSTRIP have no sens in regards to
> > extradata. This kind of "compression" just avoid duplication of redundant
> > leading bytes. But extradata only appears once, so there are no possible
> > duplication to avoid.
> 
> Specs don't say anything about this, so I assume it's possible. For example, 
> it could be applied to both extradata and data packets with 
> ContentEncodingScope = 3.

Well, spec don't prevent doing this. But still I see no sens in doing it.
I can't imagine any codec which would use some extradata and which would
write a common prefix to every packet and also to extradata.

Anyway, I've reworked your patches (but kept HEADERSTRIP decoding for
extradata), and applied.

Aurel