On Mon, Jul 21, 2008 at 11:39:14AM -0400, Art Hunkins wrote:

> Stereo ambisonic decoding in Csound never worked correctly, though I was 
> quite happy with the results of Victor's "kludge": to add four outputs each 
> of bformenc into the inputs of a stereo decode.

If your source material is Ambisonic, i.e. the output of
bformenc or any other software that generates B-format,
or from an Ambisonic microphone, then the normal way to
reproduce it in stereo is to send the summed B-format
signals to a stereo decoder. That's not a 'kludge'. 
It's not normally called a 'decoder' but a virtual
stereo microphone in that case, and you should have
the options to set the direction the mics point at,
their angle, and their polar pattern. There's no
need to write an opcode for this, it's easy enough
to code right into an instrument. Both L and R are
just linear combinations of the B-format signals.
So it's indeed just the same as panning, and if your
only intent is to produce a normal stereo signal 
their is no reason to make the detour via Ambisonics.

OTOH, if you only want to reproduce via headphones
only there is a completely different way to handle
things, and in that case it makes sense to go via
Ambisonics. You can render Ambisonics on headphones
by converting it to binaural, which means by calculating
the signals that would be generated at the listeners
ears if he/she were listening to an Ambisonic surround
system.

This is not so simple, it involves decoding the AMB
signal and then using the HRIR 'head related impulse
responses' by convolution. 

Apart from that there are techniques to make any
synthetic sound more 'natural'. They can be used
in Ambisonics, but are not 'Ambisonic' per se.

Ciao,

-- 
FA

Laboratorio di Acustica ed Elettroacustica
Parma, Italia

O tu, che porte, correndo si ?
E guerra e morte !




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