Link Search Menu Expand Document

ossia

ExprTK support

Several processes allow to write simple math expressions. Such processes include:

  • Audio Generator
  • Audio Mapping
  • Value Generator
  • Custom Mapping (Value)

ExprTK

These expressions are solved within score using the ExprTK library.

The expression can be written in the process built-in editor on multiple lines.

Numerous math functions are available: sin, cos, abs, log, as well as the usual pi, etc. constants.

Value generator

Logistic function

if(m1 == 0) {
  m2 := 0.8;
  m1 := 1;
}

var r := 4 * a;
m2 := r * m2 * (1 - m2);
m2;

Value mapper

Add jitter

var rnd_m := pow(2, 31);
var rnd_a := 1103515245;
var rnd_c := 12345;

if(m2 == 0) {
  m2 := 1;
  m1 := 12345678;
}

var r := (rnd_a * m1 + rnd_c) % rnd_m;
m1 := r;
x + a * r / (2^33);

Audio generator

Sine wave

var phi := 2 * pi * (20 + a * 500) / fs;

m1[0] += phi;

out[0] := b * cos(m1[0]);
out[1] := b * cos(m1[0]);

Square wave

var phi := 2 * pi * (20 + a * 500) / fs;

m1[0] += phi;

var f := cos(m1[0]) > 0 ? b : -b;
out[0] := f;
out[1] := f;

Wobbly synth

var freq_l := 225 +  cos(t/(100*(a+0.1)));
freq_l := 2 * pi * m1[0] *  freq_l * b / fs;

var freq_r := 215 +  sin(t/(100*(a+0.1)));
freq_r := 2 * pi * m1[0] *  freq_l * b / fs;

m1[0] += 1;

out[0] := b * cos( freq_l );
out[1] := b * cos( freq_r );

Audio filter

Crude distortion

2-channel version:

out[0] := clamp(0,  tan(x[0]*log(1 + 200 * a)), 1);
out[1] := clamp(0,  tan(x[1]*log(1 + 200 * a)), 1);

Any number of channel version:

var n := x[];

for (var i := 0; i < n; i += 1) {
  var dist := tan(x[i]*log(1 + 200 * a));
  out[i] := clamp(0, dist, 1);
}

Available variables

Everywhere

  • t: the current time
  • pos: the position in the interval
  • a, b, c: three provided controls
  • m1, m2, m3: three provided variables (which will keep their value across a tick)
    • In the audio cases they are arrays.

Value mapping

  • x: the value of the current input
  • dt: the time delta

Audio mapping

  • x: the value of the current sample
  • out: where to write the output
  • px: the value of the previous sample
  • fs: the sampling rate

Value generator

  • dt: the time delta

Audio generator

  • out: where to write the output
  • fs: the sampling rate