[Matroska-devel] New SimpleBlock

Steve Lhomme steve.lhomme at free.fr
Sat Oct 8 10:19:42 CEST 2005


OK, some comments on this:

- It will break playback of some files in all older players as there is 
a track they recognize but they never find a BlockGroup for. In that 
case we should bump the Matroska min version number (DocTypeReadVersion 
in the EBML header) to 2 as well as the Matroska version number 
(DocTypeVersion). But I'm not sure any current player verify that they 
match the required version (in that case they are not spec 
compliant...). So I suggest we go without any change (and implement that 
check where we can). It won't be a big problem as this new SimpleBlock 
won't be used by default.

- The Frames in the SimpleBlock have no duration. That means SimpleBlock 
is not suitable for VFR content (VFR video or Vorbis). Or we could fall 
back in using BlockGroup when the duration of the frames are not the 
default ones...

Steve Lhomme wrote:
> Hi,
> 
> We are in the process of adding a new Block element to the specs. The 
> idea is to make it as simple as possible to write and to read. That is 
> no complex referencing system and such. So the new SimpleBlock is now at 
> the same level as BlockGroup (which then lose his mandatory feature in 
> the block). It has the same format as our good old Block, with the 
> addition of 2 flags :
> - keyframe (set when the frames of the Block are stand alone)
> - discardable (set when the frame can be safely discarded on playback)
> 
> This change was motivated by Haali and Mosu to avoid parsing the codec 
> to find references and the required timecode. There should be no problem 
> on playback as it's the way AVI and MP4 work.
> 
> Files with that new block should be available soon from mkvmerge and 
> Haali's muxer (and hopefully AVI-Mux GUI), so you'll have to update your 
> player for such files. Haali already supports it in his experimental 
> build and I'll it to VLC this week-end when mkvmerge can create such files.
> 

-- 
robUx4 on blog <http://robux4.blogspot.com/>



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