[Vorbis-dev] Vorbis Ambisonic coupling

[xiphmont at xiph.org]

On 2/10/07, Richard Lee <ricardo at justnet.com.au> wrote:
> I have a few questions.
>
> Is there a document which details the frequency banding strategy used by Vorbis?

Only as part of the spec.  In short, it's 'flexible'; you can set up
pretty much any number of subbands of any size; in practice, this
mostly has to do with codebook selection although codebook sleection
and stereo coupling scheme are usually shosen to match.

> Is it more usual to adopt eg "8 phase" at a lower frequency band before going to "4 phase"?

No.  It was 'once upon a time', but the modern encoders use only
lossless and point.

> Do the terms "8 phase", "4 phase", "point" still make sense when we are coupling 4 channels?

Yes, but only if you squint and look at one plane at a time.

Monty