Re: [ecasound] Ambisonics !?

--On Sunday, June 19, 2005 20:27 +0930 Rick Harris
<rickharris@email-addr-hidden> wrote:

> Has anyone successfully used the ambisonic plugins, or know of any
> documentation other than just being listed as plugins ?
> Some working command line examples would be priceless as all I seem to
> be able to do is create segfaults & noise.

I assume you are referring to the LADSPA plugins in the Computer Music
Toolkit (CMT). I use the first order ones all the time and have written a
few of my own that duplicate (and extend) the functionality the Soundfield
Microphone controller. Here is an example. The input is 4 mono files in
SD2 format recorded on a Mac (hence the s24_be) with a Metric Halo. They
could just as easily be mono RIFF/WAV files. The output is a 32-bit
4-channel RIFF/WAV file.

#! /bin/csh -fx
ecasound \
  -a:1 -f:s24_be,1,96000 -i:$argv[1]-W.raw -ea:400 \
  -a:2 -f:s24_be,1,96000 -i:$argv[1]-X.raw -erc:1,2 -eac:0,1 -ea:400 \
  -a:3 -f:s24_be,1,96000 -i:$argv[1]-Y.raw -erc:1,3 -eac:0,1 -ea:400 \
  -a:4 -f:s24_be,1,96000 -i:$argv[1]-Z.raw -erc:1,4 -eac:0,1 -ea:400 \
  -a:1,2,3,4 \
  -o loop,1 \
  -a:5 -i loop,1 \
  -f:32,4,96000 \
  -el:bf_rotate_y,-10.0 \
  -el:bf_2_stq,120.0,0.65,270.0,0.75,1.0 \
  -el:singlePara,8,12000,2.5 \
  -el:singlePara,3,80,1.0\
  -o $argv[2].wav

bf_rotate_y is my plugin that performs a rotation around the left-right
axis (elevation or tumble), here 10 degrees down. bf_2_stq is also my
plugin that derives a front and back pair of microphones. It takes 5
parameters. In this example, the front mics are separated by 120 deg and
have a directivity of 0.65 (where 0=omni, 0.5=cardioid, 1.0=fig-8) and the
back pair are separated by 270 degrees with a directivity of 0.75, and the
gain of the back pair relative to the front is 1.0. Let me know if you
want them.

I also use them with jack-rack and you can see a screen shot at towards the
bottom of http://www.ai.sri.com/ajh/audio/hd-recorder-project/

--
Aaron Heller <heller@email-addr-hidden>
Menlo Park, CA
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