[CM] ambix ambisonics command line

[Juan Reyes]

Hi Anders,

Thanks a lot for your thorough explanation which of course as usual is
useful and encouraging. What I was looking for was something like
'tetrafile'. (Been using other Fons' software for a while and don't know
how I overlooked at it).

Need to encode few dozen sound files into B-format Ambisonics and batch
processing would be a time saving alternative. Will be following your
suggestions.

However, while searching this topic, can't help pointing out Fernando's
Ambisonics code in 'dlocsig.clm (scm)'.

    -- Juan


> 

> If all you want is the MS-type matrixing it should be straight
> forward in an "a2b.scm" script for snd, or sox or ffmpeg or others,
> You can combine the 4 A-format channels FLU,FRU,BLU,BRD using 
> MS-like-techniques:
> 
> W = FLU+FRD+BLD+BRU X = FLU+FRD-BLD-BRU Y = FLU-FRD+BLD-BRU Z =
> FLU-FRD-BLD+BRU
> 
> But leaving out all the required tunings for A2B conversion from any 
> given FAO mic: eq, gain, phase - you wont get any meaningful
> B-format output - rather a
> "quite-nice-space-like-feeling-surround-spread mic" (wow, my new
> brand!  :-) .
> 
> For B-format you'll need a specific B-format encoder to a specific
> type of mic, tuned to its geometry and specs of capsules, and further
> using precise calibration-data fitted to your personal mic (*).
> 
> Fons Adriansens 'tetraproc' includes a CLI 'tetrafile', doing the
> A-B conversion for Core Sounds Tetramic, and similar for their
> 2nd-order Octomic.  I think he has some example *.tetra config-files
> for some other brands.  He also offers to do the necessary
> measurements and calibrations for your TetraMic to plug into his
> conversion tools.
> 
> Not sure what the other brands - Sennheiser, Röde etc. - offers for 
> CLI-versions of their tools.
> 
> (*) The dependence on both a specific decoder for a mic-brand, and 
> further individually calibrated per mic, is perhaps sub-realised? 
> Strange, given Ambisonics 100% reliance on extremely exact phase and 
> gain info to represent the recorded space.
> 
> One example is Nevaton who provides their VR-mic - otherwise very
> nicely made with great sound (no-noise, full-range - and very
> expensive) - without neither a fitting A2B decoder or necessary
> calibration data for each mic, relying on a one-time measurement of
> one mic done by Angelo Farino.  They even have suggested using
> Sennheisers or Röde's standard A2B-encoder...
> 
> -anders
>