[Vorbis-dev] 5.1 surround channel coupling

[Richard Lee]

> May I ask what this "pan filter" is?

>It's an Ambisonic encoder which uses Furse-Malham equations to convert WAVE-EX files (the format itself is a set of speaker feeds) or a .wav file produced by an A52 decoder (mplayer is preferable as it does not truncate the LFE channel), into a set of Ambisonic channels, up to 2nd order.

Wow !  What you've got is a 2nd order Ambisonic panner or B-format encoder which translates any source (speaker) position into its proper Ambisonic representation.

What this means is you can represent 5.1, 7.1 ...  zillion.1 with just 3 channels for horizontal sound, 4 channels for full sphere sound and play it back with as few or as many speakers as the wife will allow in the room.  All without losing specificity.

The extra channels with 2nd order B-format make the resulting directions more accurate if you have more speakers.

But you can playback with less speakers and still get the best possible results with your 4 speakers.  All directions are still represented, just not as pin-pont as with more speakers.

Many thanks Sebastien.

But I don't see where you encode all this into Vorbis.  Is this still to be decided?

And am I asking the right people about frequency banding and phase?  If I'm in the wrong place, please tell me to go forth & multiply.



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