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bformdec2

Decodes an Ambisonics B format signal into loudspeaker specific signals, with dual--band decoding and near--field compensation.

Syntax

aout[] bformdec2 isetup, abform[], [idecoder, idistance, ifreq, imix, \
                 ifilel, ifiler]

Initialization

isetup -- loudspeaker setup. There are currently 8 supported setups, the first five are backwards compatible with bformdec1:

(Note that horizontal angles are measured anticlockwise in this description.)

  • 1: Stereo -- L(90), R(-90); this is an M+S style stereo decode.
  • 2: Quad -- FL(45), BL(135), BR(-135), FR(-45). This is a first-order decode.
  • 3: 5.0 -- L(30), R(-30), C(0), BL(110), BR(-110). This is the configuration suggested by the International Telecommunication Union for 5.1 surround systems for music listening. This is a first- or second- order decode.
  • 4: Octagon -- FFL(22.5), FLL(67.5), BLL(112.5), BBL(157.5), BBR(-157.5), BRR(-112.5), FRR(-67.5), FFR(-22.5). This is a first-, second- or third-order decode, depending on the number of input channels.
  • 5: Cube -- FLD(45,-35.26), FLU(45,35.26), BLD(135,-35.26), BLU(135,35.26), BRD(-135,-35.26), BRU(-135,35.26), FRD(-45,-35.26), FRU(-45,35.26). This is a first-order decode.
  • 6: Hexagon -- FL(30), L(90) BL(150), BR(-150), R(-90), FR(-30). This is a first- or second- order decode.
  • 21: 2D binaural configuration. This first decodes to a octagon configuration and then applies HRTF filters.
  • 31: 3D binaural configuration. This first decodes to a dodecahedron configuration and then applies HRTF filters.

idecoder -- optional (default 0), select the type of decoder

  • 0: Dual decoder (velocity and energy decoders using dual-band splitting).
  • 1: Velocity decoder.
  • 2: Energy decoder.

idistance -- optional (default 1 meter), select the distance (in meters) to the loudspeaker (radius if regular configuration)

ifreq -- optional (default 400 Hz), frequency cut (Hz) of the band splitting filter (only has an effect if idecoder=0)*

imix -- optional (default 0), type of mix of the velocity and energy decoders' outputs

  • 0: Energy
  • 1: RMS
  • 2: Amplitude

ifilel -- left HRTF spectral data file

ifiler -- right HRTF spectral data file

📝 Note

Spectral datafiles (based on the MIT HRTF database) should be in the current directory or the SADIR (see the hrtfstat documentation).

Performance

abform -- input signal array in the B format

aout[] -- loudspeaker specific output signals

The opcode receives as input an audio type array with an Ambisonics signal, and outputs another array with a multichannel audio signal decoded according to the given setup.

See also

Panning and Spatialization: Ambisonics

Credits

By: Pablo Zinemanas, Martín Rocamora and Luis Jure, 2019. Adapted by John ffitch

Based on code from the Ambisonics Decoder Toolbox by Aaron J. Heller.

For more information about the opcode and technical details see: Pablo Zinemanas, Martín Rocamora and Luis Jure. Improving Csound's Ambisonics decoders. Fifth International Csound Conference -- ICSC2019. Italy, 2019 -- PDF.

New in version 6.17