[CM] ambix ambisonics command line

[Juan Reyes]

Well!...

I see I don't need 'tetrafile' command. Thanks for pointing it out,
and for a good in-depth explanation.

Good that a workflow was shown. Otherwise I would be tweaking my
perception into creative aesthetic dimensions and it is not what I wanted.

Sound file is a four or eight channels file generated on CLM or Snd.
Four channels is as follows:

FLU is channel 0 (FL); FRD is channel 1(FR);
BLD is channel 2 (RL); BRU is channel 3(RR);

On each channel I'm using intensity panning.

Don't know W,X,Y,Z equations for an eight channels sound file using
LFU,RFU,RBU,LBU,LFD,RFD,RBD,LBD signals.

Guessing now, writing a panning encoder function that takes signal and
azimuth parameters also makes sense.


Thanks again!

   -- Juan

> No microphone? Hmmm, I don't understand ... how was the four channel 
> "A-format" file created?
> 

> 
> These equations already transform capsule signals (FLU, FRD, etc) into a 
> B-format four channel Ambisonics signal. If I understand correctly you 
> are using these equations, right? (one question is, where are FLU,FRD, 
> etc, coming from if not from a microphone?).
> 
> If that is what you are doing, you are already getting a WXYZ Ambisonics 
> first order signal, no need to further process it. Whether this is 
> really "Ambisonics" depends on where FLU/FRD/BRU/BLD come from...
> 

> 
> The equations you reference above transform four capsule signals into 
> first order Ambisonics assuming all capsules are identical, and they are 
> co-located (impossible in a real microphone). Unless I misunderstand 
> what you are doing, you do not need to use tetrafile, you already have a 
> four channel B-format signal.
> 
> ".tetra" files hold calibration data for individual microphones which 
> includes gain compensation for the individual capsules and frequency 
> response compensation in the mid and high frequencies that tries to 
> correct for the effects of the capsules not being co-located (they 
> contain a 4x4 matrix of convolution kernels - filters - that take 
> everything into account - I have generated that data for my DIY 3d 
> printed microphones from my measurement data).
> 
> Each calibration data set corresponds to actual measurements of a 
> particular microphone so, technically, it does not make sense to use 
> them for any other microphone.
> 
> ...
> 
> Now, artistically you can do whatever you want, of course! Does not 
> matter if it makes technical sense or is proper Ambisonics, if you like 
> what you hear go for it...
> 
> Best,
> -- Fernando
> 
> See this for more details:
> https://ccrma.stanford.edu/~nando/publications/sphear.pdf
>