[Vorbis] multi channel Ogg Vorbis file corruption

[Robert Bailey]

Has anyone else created Vorbis files with more than 6 channels?  I'm a  
game developer trying to use multichannel Ogg Vorbis files for a PS3  
and XBOX 360 title.  Using the latest release libs and tools, I've  
created a Mac application that weaves up to 8 stereo AIFF files into  
one 16 channel Ogg file.  What I'm finding is that if anything more  
than 3 stereo files (corresponding to a 5.1 audio file) are encoded,  
then the encoded output becomes unstable.  I hear vocoder like  
artifacts and garbled output on some of the stereo pairs.  It should  
be noted that I'm using a linear permutation matrix, so that the  
output file maintains the original stereo pairs, ie 16 channels in ->  
16 channels out.
I've built Universal Binary versions of the latest Ogg and Vorbis libs  
available for download, and meticulously tested my sample_read  
callback, and everything is doing the right thing.  I've even built  
raw and AIFF versions of a 16 track file, verified the integrity of  
the data,  and run them through the readily available command line  
encoders for PC and Unix.  The output corruption is identical to what  
I experience on my own encoder.   The Vorbis encoder code itself is  
extremely dense, and I suspect that any fix will be the domain of the  
authors
So has anyone else had this experience?  As Ogg Vorbis is open source,  
has anyone put up a patch for this?  Its incredibly frustrating, and  
seems to be content dependent.  In some file groupings, it performs  
brilliantly (I love the sound of Vorbis much more than MP3) for 3  
minutes, and then goes to crap.  In others, the corruption is evident  
much earlier.   It always appears at the same place for each file  
group, no matter what the encoding settings.   Any and all advice is  
greatly appreciated.


Robert Bailey
rob at the-treehouse-studio.com