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Signal Modifiers: Panning and Spatialization

locsig, locsend

  a1, a2            locsig    asig, kdegree, kdistance, kreverbsend
  a1, a2,  a3, a4   locsig    asig, kdegree, kdistance, kreverbsend
 
  a1, a2            locsend
  a1, a2,  a3, a4   locsend

Description

locsig takes an input signal and distributes it among 2 or 4 channels using values in degrees to calculate the balance between adjacent channels. It also takes arguments for distance (used to attenuate signals that are to sound as if they are some distance further than the loudspeaker itself), and for the amount the signal that will be sent to reverberators. This unit is based upon the example in the Charles Dodge/Thomas Jerse book, Computer Music, page 320.

locsend depends upon the existence of a previously defined locsig. The number of output signals must match the number in the previous locsig. The output signals from locsend are derived from the values given for distance and reverb in the locsig and are ready to be sent to local or global reverb units (see example below). The reverb amount and the balance between the 2 or 4 channels are calculated in the same way as described in the Dodge book (an essential text!).

Performance

kdegree – value between 0 and 360 for placement of the signal in a 2 or 4 channel space configured as: a1=0, a2=90, a3=180, a4=270 (kdegree=45 would balanced the signal equally between a1 and a2). locsig maps kdegree to sin and cos functions to derive the signal balances (ie.: asig=1, kdegree=45, a1=a2=.707).

kdistance – value >= 1 used to attenuate the signal and to calculate reverb level to simulate distance cues. As kdistance gets larger the sound should get softer and somewhat more reverberant (assuming the use of locsend in this case).

kreverbsend – the percentage of the direct signal that will be factored along with the distance and degree values to derive signal amounts that can be sent to a reverb unit such as reverb, or reverb2.

Example

  asig some audio signal
  kdegree            line    0, p3, 360
  kdistance          line    1, p3, 10
  a1, a2, a3, a4     locsig  asig, kdegree, kdistance, .1
  ar1, ar2, ar3, ar4 locsend
  ga1 = ga1+ar1
  ga2 = ga2+ar2
  ga3 = ga3+ar3
  ga4 = ga4+ar4
                     outq    a1, a2, a3, a4
endin

instr 99 ; reverb instrument
  a1                 reverb2 ga1, 2.5, .5
  a2                 reverb2 ga2, 2.5, .5
  a3                 reverb2 ga3, 2.5, .5
  a4                 reverb2 ga4, 2.5, .5
                     outq    a1, a2, a3, a4
  ga1=0
  ga2=0
  ga3=0
  ga4=0

In the above example, the signal, asig, is sent around a complete circle once during the duration of a note while at the same time it becomes more and more "distant" from the listeners' location. locsig sends the appropriate amount of the signal internally to locsend. The outputs of the locsend are added to global accumulators in a common Csound style and the global signals are used as inputs to the reverb units in a separate instrument.

locsig is useful for quad and stereo panning as well as fixed placed of sounds anywhere between two loudspeakers. Below is an example of the fixed placement of sounds in a stereo field.

instr 1
  a1, a2             locsig  asig, p4, p5, .1
  ar1, ar2           locsend
  ga1=ga1+ar1
  ga2=ga2+ar2
                     outs a1, a
endin
instr 99 
  ; reverb....
endin

A few notes:

  ;place the sound in the left speaker and near:
  i1 0 1 0 1
  
  ;place the sound in the right speaker and far:
  i1 1 1 90 25
  
  ;place the sound equally between left and right and in the middle ground distance:
  i1 2 1 45 12
  e

The next example shows a simple intuitive use of the distance value to simulate Doppler shift. The same value is used to scale the frequency as is used as the distance input to locsig.

  kdistance          line    1, p3, 10
  kfreq = (ifreq * 340) / (340 + kdistance)
  asig               oscili  iamp, kfreq, 1
  kdegree            line    0, p3, 360
  a1, a2, a3, a4     locsig  asig, kdegree, kdistance, .1
  ar1, ar2, ar3, ar4 locsend

Author

Richard Karpen
Seattle, Wash
1998 (New in Csound version 3.48)


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Signal Modifiers: Panning and Spatialization