[Vorbis-dev] 5.1 surround channel coupling

[Richard Lee]

> Is there any reason why the panner shouldn't have a default
configuration matching the standard ITU layout and only expose the
fully flexible layout as an advanced option?

There are 2 important reasons for not doing this

1)	No one has an ITU layout at home.  The only one I know of is in a big research lab.  I discuss this in "Ambisonic Surround Decoder" under Real World Systems

www.ambisonicbootlegs.net\Members\ricardo

2)	It doesn't give as good results as simple 4.0 square.  This is predicted by Ambisonic theory.  That's why 5.1 can't put images at the sides.

This doesn't just apply to Ambisonics on 5.1 but anything played on an ITU 5.1 layout.

Benjamin, Lee & Heller are currently testing this very proposition in the sequel to "Localization in Horizontal-Only Ambisonic Systems"

www.ai.sri.com/ajh/ambisonics

Richard Elen, Ambi guru and one time editor of Studio Sound recently coded some Ambisonic square 4.0 speaker feeds into a DTS-CD and went round to his friends with surround systems.

He reports that my Real World System is very representative and results were excellent.  Also that listeners instinctively moved forward so they were in the centre of the square.  This is of course where the best sound is for square 4.0
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So from theory & practice, a default surround Speaker Decode should be simple 4.0 as in the Wiki Ambisonic Decoding page.

Better Speaker Decoders for ITU style layouts will come but in every case, a regular layout will give better results if we apply the same effort.

Today, with 21st century digits, you can get reasonable stereo without identical speakers the same distance from the listener.  But you ALWAYS get better results with matched equidistant speakers.


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