[Matroska-devel] CodecPrivate for MPEG-1 and MPEG-2 video

Steve Lhomme steve.lhomme at free.fr
Tue Nov 16 15:35:44 CET 2004

Moritz Bunkus a écrit :
> Hey,
> Let's talk about V_MPEG1 and V_MPEG2 :) Our specs page says:
>   The matroska video stream will contain a demuxed Elementary Stream
>   (ES), where block boundaries are still to be defined. Its recommended
>   to use MPEG2MKV.exe for creating those files, and to compare the
>   results with selfmade implementations
> Spyder has told me he puts a sequence header into the CodecPrivate. The
> sequence header contains information like width, height, FPS and pixel
> aspect ratio among other things. While some of these fields are present
> in the Matroska track headers others are not (like the picture coding
> extension). So we cannot simply drop it.
> Personally I'm voting for not putting anything into the the
> CodecPrivate. At least not as mandatory information. The muxing app
> MAY put a sequence header there, e.g. if the MPEG ES doesn't start with
> one (every MPEG decoder needs a sequence header before it can decode the
> data).
> Spyder? Any preference, additional thoughts?

Well, that's quite a change. Because so far we always assume the 
CodecPrivate is filled for each CodecID. Having an optional CodecPrivate 
wasn't discussed so far (?). IMO eitherr we have it, or not. But in 
between is only hacky for no good reason. It's up to spyder to tell if 
we need the missing data or not.

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