[Vorbis] multi channel Ogg Vorbis file corruption

[Michael Smith]

The libvorbis encoder only treats stereo specially. Any other number
of channels - 1, 3, 6, or 16 - are encoded simply as that number of
independent channels.

So, corruption specific to the channel count is fairly unlikely
(though of course not entirely impossible). It's also not something
that sounds at all familiar.

Since you say you've tested this on other platforms, a compiler bug
seems unlikely.

Can you make one of these corrupt files available for people to take a look at?

Mike


On Wed, Jul 9, 2008 at 7:48 AM, Robert Bailey
<rob at the-treehouse-studio.com> wrote:
> 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
>
>
>
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