[vorbis] Multichannel vorbis.

[rillian]

On Thursday, July 19, 2001, at 07:34 , Aaron Plattner wrote:

> As a side question, will Vorbis directly encode Dolby Digital streams 
> somehow,
> or will there be a Dolby Digital to Ambisonics stage first?  It seems 
> to me
> that since Dolby Digital is just planar audio, it should be possible to 
> encode
> it in a 3-channel Ambisonic format, although I don't know how well that 
> would
> work for movies with speech only in the front.

I assume you mean 5.1 surround, rather than 'Dolby Digital' which 
commonly means AC3. I don't think anyone's decided yet. Ambisonics is 
better technology, but 5.1 seems to be becoming as established a 
standard as l/r stereo.

No one with a test rig has come forward with empirical results, but I 
wouldn't expect 3-channel ambisonics would work for movie sound. The 
whole point of the three forward channels is to give accurate imaging 
over the space of the screen. You'd need 6 channels to do planar imaging 
with that kind of directionality. And finally, it's not clear what do do 
with the low frequency effects channel (the .1). Dolby says you're free 
to ignore it or mix it in with the others, of course.

The counter-argument would be that if we don't insist on native 
ambisonic surround, it'll end up being an optional feature and everyone 
will go with 5.1. And then we'll get to add 7.1 if/when that becomes 
more common.

  -r

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