This directory contains two sets of FIR filters for the Brahma prototype.
These filters are in 4x4 format, as they process a 4-input stream (the
A-format signal, which means the capsules FLU, FRD, BLD, BRU) and converts 
them in standard B-format (WXYZ) for further Ambisonics processing.
For performing the convolution of the input stream with the FIR filters
it is suggestd to employ an host program such as Synthedit, Plogue Bidule or Audiomulch.
A 4-channel WAV player is employd for getting the A-format signals from the
stereo recordings done by the Zoom H2 recorder.
The 4 signals are passed through Xvolver (a VST plugin, which needs to be setup 
for 4 inputs and 4 outputs), and finally the resulting 4 signals are routed 
to a 4-channels WAV writer.
Xvolver must be setup for performing convolution of impulse response 16384 points
long, with an FFT size of 2048 samples. Before loading the FIR filters, select the
IR multi mode, then browse to the directory where the filters are saved and select 
one of them.
The filter will be automatically splitted in 16 indipendent FIRs, loaded properly in the
cells of the 4x4 convolution matrix.
Once the filters are loaded, you can close the interface of Xvolver, and launch the 
Record & Playback process. If using Bidule, enter the "offline" mode, for performing
the processing faster than in realtime. On a modern multicore processor, you can easily
attain a performance boost by a factor 10 or more (that is, filtering a 10-minutes 
recording in less than one minute).
Of course, you could create a more complex patch, in which the B-format outputs of
Xvolver are routed directly to an Ambisonics decoder or to the Visual Virtual Microphone
plugin, for realtime rendering over a loudspeaker rig.... 

(C) Angelo Farina, December 2008