[Vorbis-dev] Re : Ambisonics in Ogg Vorbis

[Richard Lee]

>I have been giving some thought to how to include Ambisonics in Ogg Vorbis.

As I understand it, 

mapping type = 1

was meant from the start to indicate an Ambisonic stream.  The only other information required is the number of channels which thanks to Mr Leese's clever trick tells us exactly which Ambisonic channels are used up to 3rd order.
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>The channel coupling wont be optimal and the phase may get a bit munged (Ambisonics is big on low-frequency phase), but it will work.

Can we stop perpetuating this myth.

>From the previous discussions on coupling and phase, it should be obvious (to yus DSP gurus) that all coupling methods that are likely to be used with an Ambisonic (or indeed any multichannel) stream will preserve phase.

The phase mucking methods have not been implemented.
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So from the above, a Vorbis codec is straightforward.  It only remains for a DSP guru to implement this for a common multi-channel player like VideoLAN or Windoz Media Player.

Sebastien Olter is doing some code which will be useful towards this end.

Windoz Media Player already has a good Ambisonic B-format to speaker decoder courtesy Bruce Wiggins' WAD

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

These should work with any DirectShow capable players too.

If you are a DSP guru planning to do this for Windoz Media Player, please contact Bruce to make sure your decoder will feed WAD correctly in WMP.



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