[FFmpeg-devel] [PATCH] attachments support in matroska demuxer

Reimar Döffinger Reimar.Doeffinger
Sun Jan 20 21:01:14 CET 2008

On Sun, Jan 20, 2008 at 07:25:21PM +0000, M?ns Rullg?rd wrote:
> Uoti Urpala <uoti.urpala at pp1.inet.fi> writes:
> > On Sun, 2008-01-20 at 18:38 +0000, M?ns Rullg?rd wrote:
> >> No, I mean the opposite.  It is impossible for a demuxer to identify
> >> an unsupported codec in a container-independent fashion.
> >
> > Where did you get "container-independent" from?
> In all other matters, Michael insists that everything in FFmpeg be
> independent of any particular implementation.  I fail to see what's so
> special about the codec identifier used by the container.

Well, the special thing is as you mentioned above that it is impossible
to do in a container-independent way.

> > I specifically talked about "exporting the container-specific codec
> > type information". And Michael said in an earlier message "codec_tag
> > is intended to identify the codec in a container specific way".
> Well, it's not doing a very good job of that.  Being an 'unsigned
> int', it has no chance of representing e.g. matroska codec
> identifiers.

e.g.? So far matroska seems like the only problematic case to me, at
least among the containers we support.

> To be generic, it would have to be a pointer/size pair
> like extradata.

That as well has a load of problems like defining a way to represent
all the different places where such codec information may or may not be
or the combination of (excuse if I get the names wrong) codec and stream
fourcc for AVI (that people like to misuse in every way imaginable).
Though of course it is possible to store all of these in a pointer/size
pair but without a sane way to do it the pure possibility is not worth
that much.

> Some people have really close horizons.

Some people are really predictable. I'm starting to wonder if maybe you
were somewhen hunted by a wild AVI or what causes that allergic reaction
;-) (you can't seriously believe we do not see AVI's metric ton of
problems unless you beat it into us?...)

Reimar D?ffinger

More information about the ffmpeg-devel mailing list