DP2PWM
Low CPU Anti Aliased Pulse Width Modulated Osc (Second order differentiated polynomial).
Inlets
frac32.bipolar pitch
frac32.bipolar pw
Outlets
frac32buffer.bipolar selfPM wave
Parameters
frac32.s.map.pitch pitch
frac32.u.map Pulse Width
Declaration
float pa, pb, dp, _dp2, y0, y1, y2;
float I2(float p) { return p * (1 / 6.0f + p * (-0.5f + p * (1 / 3.0f))); }
Init
pa = pb = y0 = y1 = y2 = 0.0f;
Control Rate
int32_t idp;
MTOFEXTENDED(param_pitch + inlet_pitch, idp);
dp = idp * (0.25f / (1 << 30));
_dp2 = (1 << 27) / (dp * dp);
float pw = param_pw * (1.0f / (1 << 27)) + inlet_pw * (1.0f / (1 << 27));
if (pw < 0.05f) {
pw = 0.05f;
}
if (pw > 0.95f) {
pw = 0.95f;
}
pb = pa + pw;
pb -= (pb > 1);
// change of dp => update state variables y1 y2
pa -= dp;
pa += (pa < 0);
pb -= dp;
pb += (pb < 0);
y2 = I2(pa) - I2(pb);
pa += dp;
pa -= (pa > 1);
pb += dp;
pb -= (pb > 1);
y1 = I2(pa) - I2(pb);
Audio Rate
pa += dp;
pa -= (pa > 1);
pb += dp;
pb -= (pb > 1);
y0 = I2(pa) - I2(pb);
outlet_wave = (int32_t)((y0 + y2 - 2 * y1) * _dp2);
y2 = y1;
y1 = y0;