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

Cyrius suiryc at yahoo.com
Wed Nov 17 12:02:16 CET 2004

--- John Cannon <spyder at matroska.org> wrote:

> Paul Bryson wrote:
> > I'm sure we've had this discussion before.  I don't feel like
> actually 
> > tracking it down in the ML, but it was early in the year, February
> maybe? 
> > Anyway, It should be optional.  If the headers are identical for
> each GOP, 
> > then why would a decoder need them repeated all the time?
> It _IS_ optional.  The MPEG-2 spec allows the headers to be repeated
> as 
> often as the encoder desires. The only requirement is that there be 1
> somewhere and also that the parameters stay basically the same except
> for a few elements.  The spec recommends they be placed before each
> GOP 
> for faster seeking and easier editing but AFAIK there is no
> requirement. 
>     I don't want to have to reconstruct the stream on demux though. 
> So 
> I vote for leaving the stream intact.
> John

Plus when demuxing you wouldn't always get back the original stream
(since it may have only one header at the beginning of the stream).
I would also vote for keeping the stream intact (since overhead impact
isn't big) and have a copy of the first header in the CodecPrivateData
(for frameworks needing such data beforehand).

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