NAME
ambdec - Ambisonic decoder for first and second order
SYNOPSIS
ambdec [options]
ambdec_cli config_file
DESCRIPTION
This manual page documents briefly the ambdec and ambdec_cli commands.
AmbDec is an Ambisonics decoder for up to 36 speakers. It can be used
for both horizontal and full 3-D systems of first, second and third
order. The decoding matrices are fully user-configurable. AmbDec has
some advanced feautures not found on most decoders:
Dual frequency band operation. Optimal Ambisonics reproduction
requires a different decoder for low and high frequencies. This is so
mainly because human perception of sound direction uses different
mechanisms at low and high frequencies. The crossover filters used in
AmbDec are phase-aligned (the two outputs are exactly in phase at all
frequencies). The combined response is equivalent to a first-order all-
pass network, which is very probably inaudible.
Speaker distance compensation. If the speakers are not all at the same
distance to the center of the listening area, this must be compensated
by including the right delays and gain corrections.
Near-field effect compensation. Ambisonics works by reconstructing the
spherical harmonic components of a sound field at the center of the
listening area, using all speakers to synthesize each of them. All non-
zero order components show a near-field effect depending on the ratio
wavelength=distance, and increasing for rising order. One example of
this is the well known ’proximity effect’ of directional microphones
(’directional’ is equivalent to ’using non-zero order components’).
Except in very large installations, where the speaker distances will be
large enough so the listening area is not in the near field, this
effect must be compensated for in order to obtain a correct
reconstruction of a sound field.
OPTIONS
ambdec accepts the following command line options:
-h Show summary of options.
-c FILE
Load configuration from FILE.
-p PATH
Load presets from PATH.
-V VOLUME
Set initial volume in dB.
AUTHOR
ambdec was written by Fons Adriaensen <fons@kokkinizita.net>.
This manual page was written by Alessio Treglia
<quadrispro@ubuntu.com>, for the Debian project (and may be used by
others).
2010/03/14