opencodecs unable to cope with less usual audio setups (ogg 6.1, possibly 7.1 and other non-stereo ones)
I tested this thoroughly with 6.1 setup (FL, FR, FC, LFE, BC, SL, SR), encoded with latest oggenc from vorbis-tools 1.4.0, as well as oggenc2 from rarewares. Looking at the oggenc/audio.c source, the encoder can (should) handle 6.1 (mask 0x70F) and a good few other ones. rarewares' oggdec also decodes properly back to wav (official vorbis-tools one produces silence).
Example files to encode can be downloaded from:
Wav file has proper wave extensible header, flac has proper "comment" - both provide mask 0x70F.
The effect from playing 6.1 ogg file is always the same - oggdsf assumes it's 2 channel file, and outputs FL and FC as left/right.
Originally I thought it was an issue with encoder, the thread for reference:
I haven't tested other channel setups yet.