[Vorbis-dev] 5.1 surround channel coupling

[Richard Lee]

>A decoding setup for ITU 5.1 is discussed on

>http://pcfarina.eng.unipr.it/Public/B-format/5_1_conversion/5_1_decoders.htm.

A good Ambi to 5.1 decode is at 

http://www.e-wig.co.uk/sursound/gformat_ac3.jpg

Bruce Wiggins has good Decoders using this and for other layouts at 

http://sparg.derby.ac.uk/SPARG/Staff_BW.asp

More useful than the Vienna decodes

But you get much better results if you decode to a square or rectangle 4.0 layout.

"Ambisonic Surround Decoder" from

ambisonicbootlegs.net\Members\ricardo

discusses this and has more references.

The definitive document on horizontal Classic Ambisonic Decoders is

"SHELF FILTERS for Ambisonic Decoders" from the above site.

>but it's a much easier problem for a lossless codec.  right now, except for stereo, channels are always coded independently, mainly because I haven't done much research into patent-free multichannel decorrelation schemes.

Ambisonic B-format has a lot in common between channels.  So there might be an argument for coupling each of the XYZ velocity signals to the W omni signals.

But there is a caveat.  Does Vorbis coupling preserve "phase" relations?  Any references explaining this in simple detail?
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