[Matroska-devel] [Fwd: Re: Dirac mapping for Matroska]

[Steve Lhomme]

Sebastian Dröge wrote:
> Ok, after talking to one of the Dirac developers I'd like to change the
> previous proposal completely ;)
> 
> The plan would now be:
> - CodecID is "V_DIRAC"
> - No CodecPrivate, no changing of the stream
> - A Matroska block/lace contains all Dirac packets up to and
>   including a picture. This means, all padding, maybe a sequence
>   header and maybe auxiliary data and then the picture for which
>   all this previous data was. This makes demuxing much easier
>   and prevents broken streams created by a muxer or demuxer.

I liked the previous proposal better. Is there a reason why you to store 
metadata in the "playback blocks" ? Only data needed for decoding should 
be put in a cluster. There is room for plenty of metadata elsewhere 
(tracks, tags, chapters and more can be added if necessary). Does it 
also include padding ???

> - A block is a keyframe whenever it contains a sequence header.
>   Sequence headers are added to the stream by the encoder at
>   places that are meant as "seek points" and on which decoding
>   could start. There's no easy way of detecting whether a picture
>   can be decoded on it's own in any other way.

That means only those frames with a sequence header should be marked as 
keyframes in SimpleBlock. I'm not use using the other "reference system" 
is necessary.

> The Track elements can contain the video width/depth, aspect ratio,
> framerate etc but that's not required. Also setting the ReferenceBlock
> element is not necessary.
> 
> What do you think? This is rather easy to implement, allows all
> flexibility and makes sure that the Dirac streams are not damaged ;)

You mean it's as close to the original as possible. Except it doesn't 
take of matroska to store the data in the appropriate place. Using VfW 
will give the same (bad) result.

Steve