[Vorbis-dev] Ambisonics in Ogg Vorbis

[Paul Martin]

On Wed, Apr 25, 2007 at 10:01:10AM +1000, Richard Lee wrote:
> > I have done. How does that relate to my pointing out the fact that
> > the W channel is stored 3dB down in an .amb file? Well, it changes
> > the decode, doesn't it?
> 
> In "SHELF FILTERS ... ", I use WXYZ in its strict Ambisonic sense
> as defined in
> 
> http://www.york.ac.uk/inst/mustech/3d_audio/secondor.html

You're dancing round the question. The specification of an AMB file
says that the W channel will be stored at a level of -3dB.

http://www.ambisonia.com/Members/etienne/Members/mleese/file-format-for-b-format

"The W channel is attenuated by -3 dB (1/sqrt(2)) for all orders.
That is to say, a source at 45 degrees azimuth (zero elevation) would
produce equal gains in W, X, and Y."

This means that my decode *is* the "Energy" one.

-- 
Paul Martin <pm at zetnet.net> (work)
  <pm at nowster.zetnet.co.uk> (home)