[Matroska-devel] WavPack in Matroska

Steve Lhomme steve.lhomme at free.fr
Fri Jul 2 16:33:43 CEST 2004


As some of you may know, there is an hybrid mode in Wavpack. That means 
that you can encode a PCM file losslessly but it will be split in 2 
parts : a lossy file with a (somehow) given bitrate and another file to 
complement the lost data. I hope I get the idea right...

IMO this is a killer feature (not found elsewhere ?) because it allows 
you to have a good quality lossy file format (that hopefully could be 
used even in portable players) and at the same time you can keep the 
original losslessly.

Not about the muxing...

Right now the result is encoded in 2 files : one for the lossy data and 
one for the complementary data. But how do we allow this in Matroska ?

- We could also use 2 files. But IMO that's not very clean even though 
the possibility should exist. In this case we should have a way to 
identify matching pairs inside the container. This way even if you 
rename the 2 files, you can manage to rematch them later. The MD5 sum 
computed by WavPack could be used for that

- Put the 2 "parallel" streams in one Matroska file. The options are :

* have a track for each, which a codec ID for each, each distinct from 
the normal codec ID of WavPack

* have the lossy in one track and the complement attached (since it 
can't be used without the lossy part)

* have both muxed in a single track. Maybe that's the way a normal 
WavPack block is done, so it would be fully compatible with the normal 
WavPack codec ID. We would only need a different codec ID when the 
complement is not put in the track.

What do you think ?

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

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