[Vorbis-dev] Multichannel Vorbis encode

[Lucas Clemente Vella]

xiphmont at xiph.org escreveu:
> Vorbis channels are explicitly in ASTM/ETSI order, that is, the
> traditional channel order for eight track theater sound and the same
> as AC3..   all compliant AC3 decoders should be in the same channel
> order as Vorbis as they're all using the same spec.  So FFMPEG is
> apparently rearranging the channels out of the correct order and then
> needs a libvorbis patch to undo it...????  That doesn't seem right.
> Something is confused (or just forgetting there are systems other than
> Windows out there).
> 
> Regardless of what's actually going on in ffmpeg, remapping
> functionality doesn't belong in every codec, it belongs in the
> framework.  Libvorbis is already used in many systems that are able to
> remap channels between codecs, adding that functionality to libvorbis
> too is just bloat.  If ffmpeg needs to rearrange channels (it must be
> able to, to have rearranged the AC3 output into SMPTE) it should
> rearrange the channels, not force every codec to change to what it
> wants to pass.
> 
> Eg, it turns out that ogg123 wasn't able to handle different channel
> orders, so the proper place to fix it (just added to SVN last night)
> is in libao, not all the codecs and loaders.  One piece of code in one
> place instead of 50.

Oh, crap!

I sent it to the wrong list. I thought I was talking in FFmpeg list, not
Vorbis list. Sorry. The patch is to FFmpeg, that still can't encode
multichannel Vorbis. Internally FFmpeg uses this SMPTE order, so we need
to rearrange the channels before passing the samples to libvorbis...

-- 
Lucas Clemente Vella
lvella at gmail.com