[Vorbis-dev] 5.1 surround channel coupling

[xiphmont at xiph.org]

On 2/28/07, Richard Lee <ricardo at justnet.com.au> wrote:

> Yes.  Good multichannel "lossless coupling" is essential.  It is this which gives DD a 2:1 advantage over DTS and allows MLP to meet the DVD-A bitrate spec.

Well, a '2:1 advantage' over anything involves alot of presuppositions
that involve getting some addiitonal ducks in a row for the lossless
coupling.  And generally, it also presupposes specific loudspeaker
playback arrangements that increase coupling of the reproduced audio,
dramatically increasing cross-channel masking. Listening to just one
channel of the average movie surround encode at a time would make any
audiophile wince.

It's like with stereo; if we toss out headphones as a playback case we
could be alot more aggressive with coupling.  That's not a direct
analogy, just an example of assumptions making a big difference in
coding strategy.

> >Monty has also cited the lack of (not lossily compressed) 5.1 sources to test with as an obstacle here.
>
> There is a large library of impressive uncompressed high quality Ambisonic recordings at
>
> www.ambisonicbootlegs.net

Ambisonic != 5.1.  Regardless I didn't know about this ambisonic
archive, and that is something I wanted very much to be told about.

(Hell, in Ghost, I'd like to see Ambisonic be _the_ way to do
surround, and if you want 5.1, you get to map it to/from Ambisonic
representation)

Monty