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babo

A physical model reverberator.

babo stands for ball-within-the-box. It is a physical model reverberator based on the paper by Davide Rocchesso "The Ball within the Box: a sound-processing metaphor", Computer Music Journal, Vol 19, N.4, pp.45-47, Winter 1995.

The resonator geometry can be defined, along with some response characteristics, the position of the listener within the resonator, and the position of the sound source.

babo2 was introduced to fix the issue of the direct sound parameter (see expert parameters), which is a non-op in the original opcode.

Syntax

a1, a2 = babo(asig, ksrcx, ksrcy, ksrcz, irx, iry, irz [, idiff] [, ifno])
a1, a2 = babo2(asig, ksrcx, ksrcy, ksrcz, irx, iry, irz [, idiff] [, ifno])

a1, a2 babo asig, ksrcx, ksrcy, ksrcz, irx, iry, irz [, idiff] [, ifno]
a1, a2 babo2 asig, ksrcx, ksrcy, ksrcz, irx, iry, irz [, idiff] [, ifno]

Initialization

irx, iry, irz -- the coordinates of the geometry of the resonator (length of the edges in meters)

idiff -- is the coefficient of diffusion at the walls, which regulates the amount of diffusion (0-1, where 0 = no diffusion, 1 = maximum diffusion - default: 1)

ifno -- expert values function: a function number that holds all the additional parameters of the resonator. This is typically a GEN2--type function used in non-rescaling mode. They are as follows:

  • decay -- main decay of the resonator (default: 0.99)
  • hydecay -- high frequency decay of the resonator (default: 0.1)
  • rcvx, rcvy, rcvz -- the coordinates of the position of the receiver (the listener) (in meters; 0,0,0 is the resonator center)
  • rdistance -- the distance in meters between the two pickups (your ears, for example - default: 0.3)
  • direct -- the attenuation of the direct signal (0-1, default: 0.5). This is a non-op in babo, but has been introduced in babo2.
  • early_diff -- the attenuation coefficient of the early reflections (0-1, default: 0.8)

Performance

asig -- the input signal

ksrcx, ksrcy, ksrcz -- the virtual coordinates of the source of sound (the input signal). These are allowed to move at k-rate and provide all the necessary variations in terms of response of the resonator.

Examples

Here is a simple example of the babo opcode. It uses the file babo.csd, and drumsMlp.wav.

A simple example of the babo opcode.
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<CsoundSynthesizer>
<CsOptions>
; Select audio/midi flags here according to platform
-odac     ;;;RT audio out
;-iadc    ;;;uncomment -iadc if RT audio input is needed too
; For Non-realtime ouput leave only the line below:
; -o babo.wav -W ;;; for file output any platform
</CsOptions>
<CsInstruments>

/* Written by Nicola Bernardini */

sr = 44100
ksmps = 32
nchnls = 2

; minimal babo instrument
;
instr 1
       ix     = p4  ; x position of source
       iy     = p5  ; y position of source
       iz     = p6  ; z position of source
       ixsize = p7  ; width  of the resonator
       iysize = p8  ; depth  of the resonator
       izsize = p9  ; height of the resonator

ainput soundin "drumsMlp.wav"

al,ar  babo    ainput*0.7, ix, iy, iz, ixsize, iysize, izsize

       outs    al,ar
endin


</CsInstruments>
<CsScore>

/* Written by Nicola Bernardini */
; simple babo usage:
;
;p4     : x position of source
;p5     : y position of source
;p6     : z position of source
;p7     : width  of the resonator
;p8     : depth  of the resonator
;p9     : height of the resonator
;
i  1  0  20 6  4  3    14.39 11.86 10
;           ^^^^^^^    ^^^^^^^^^^^^^^
;           |||||||    ++++++++++++++: optimal room dims according to
;           |||||||                    Milner and Bernard JASA 85(2), 1989
;           +++++++++: source position
e


</CsScore>
</CsoundSynthesizer>

Here is an advanced example of the babo opcode. It uses the file babo_expert.csd, and drumsMlp.wav.

An advanced example of the babo opcode.
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<CsoundSynthesizer>
<CsOptions>
; Select audio/midi flags here according to platform
-odac     ;;;RT audio out
;-iadc    ;;;uncomment -iadc if RT audio input is needed too
; For Non-realtime ouput leave only the line below:
; -o babo_expert.wav -W ;;; for file output any platform
</CsOptions>
<CsInstruments>

/* Written by Nicola Bernardini */

sr = 44100
ksmps = 32
nchnls = 2

; full blown babo instrument with movement
;
instr 2
  ixstart = p4   ; start x position of source (left-right)
  ixend   = p7   ; end   x position of source
  iystart = p5   ; start y position of source (front-back)
  iyend   = p8   ; end   y position of source
  izstart = p6   ; start z position of source (up-down)
  izend   = p9  ; end   z position of source
  ixsize  = p10  ; width  of the resonator
  iysize  = p11  ; depth  of the resonator
  izsize  = p12  ; height of the resonator
  idiff   = p13  ; diffusion coefficient
  iexpert = p14  ; power user values stored in this function

ainput    soundin "drumsMlp.wav"
ksource_x line    ixstart, p3, ixend
ksource_y line    iystart, p3, iyend
ksource_z line    izstart, p3, izend

al,ar     babo    ainput*0.7, ksource_x, ksource_y, ksource_z, ixsize, iysize, izsize, idiff, iexpert

          outs    al,ar
endin


</CsInstruments>
<CsScore>

/* Written by Nicola Bernardini */
; full blown instrument
;p4         : start x position of source (left-right)
;p5         : end   x position of source
;p6         : start y position of source (front-back)
;p7         : end   y position of source
;p8         : start z position of source (up-down)
;p9         : end   z position of source
;p10        : width  of the resonator
;p11        : depth  of the resonator
;p12        : height of the resonator
;p13        : diffusion coefficient
;p14        : power user values stored in this function

;         decay  hidecay rx ry rz rdistance direct early_diff
f1  0 8 -2  0.95   0.95   0  0  0    0.3     0.5      0.8  ; brighter
f2  0 8 -2  0.95   0.5    0  0  0    0.3     0.5      0.8  ; default (to be set as)
f3  0 8 -2  0.95   0.01   0  0  0    0.3     0.5      0.8  ; darker
f4  0 8 -2  0.95   0.7    0  0  0    0.3     0.1      0.4  ; to hear the effect of diffusion
f5  0 8 -2  0.9    0.5    0  0  0    0.3     2.0      0.98 ; to hear the movement
f6  0 8 -2  0.99   0.1    0  0  0    0.3     0.5      0.8  ; default vals
;        ^
;         ----- gen. number: negative to avoid rescaling


i2 0 10  6  4  3   6   4  3  14.39  11.86  10    1  6 ; defaults
i2 +  4  6  4  3   6   4  3  14.39  11.86  10    1  1 ; hear brightness 1
i2 +  4  6  4  3  -6  -4  3  14.39  11.86  10    1  2 ; hear brightness 2
i2 +  4  6  4  3  -6  -4  3  14.39  11.86  10    1  3 ; hear brightness 3
i2 +  3 .6 .4 .3 -.6 -.4 .3  1.439  1.186  1.0 0.0  4 ; hear diffusion 1
i2 +  3 .6 .4 .3 -.6 -.4 .3  1.439  1.186  1.0 1.0  4 ; hear diffusion 2
i2 +  4 12  4  3 -12  -4 -3  24.39  21.86  20    1  5 ; hear movement
;
i2 +  4  6  4  3   6   4  3  14.39  11.86   10   1  1 ; hear brightness 1
i2 +  4  6  4  3  -6  -4  3  14.39  11.86   10   1  2 ; hear brightness 2
i2 +  4  6  4  3  -6  -4  3  14.39  11.86   10   1  3 ; hear brightness 3
i2 +  3 .6 .4 .3 -.6 -.4 .3  1.439  1.186  1.0 0.0  4 ; hear diffusion 1
i2 +  3 .6 .4 .3 -.6 -.4 .3  1.439  1.186  1.0 1.0  4 ; hear diffusion 2
i2 +  4 12  4  3 -12  -4 -3  24.39  21.86   20   1  5 ; hear movement
;       ^^^^^^^^^^^^^^^^^^^  ^^^^^^^^^^^^^^^^^   ^  ^
;       |||||||||||||||||||  |||||||||||||||||   |   --: expert values function
;       |||||||||||||||||||  |||||||||||||||||   +--: diffusion
;       |||||||||||||||||||  ----------------: optimal room dims according to Milner and Bernard JASA 85(2), 1989
;       |||||||||||||||||||
;       --------------------: source position start and end
e


</CsScore>
</CsoundSynthesizer>

See also

Reverberation

Credits

Author: Paolo Filippi
Padova, Italy
1999

Nicola Bernardini
Rome, Italy
2000

New in Csound version 4.09