ZoelzerMultiFilterPatch(){
registerParameter(PARAMETER_A, "Mode");
registerParameter(PARAMETER_B, "Frequency");
registerParameter(PARAMETER_C, "Resonance");
registerParameter(PARAMETER_D, "Gain");
previous.setCoefficents(coeffs);
}
void processAudio(AudioBuffer &buffer){
int mode = getParameterValue(PARAMETER_A)*ZOELZER_MODES;
float omega = (M_PI/2 - 0.01)*getParameterValue(PARAMETER_B) + 0.00001; // Frequency
float K = tan(omega);
float Q = getParameterValue(PARAMETER_C) * 10 + 0.1; // Resonance
float gain = getParameterValue(PARAMETER_D);
float V = abs(gain-0.5)*60 + 1; // Gain
float norm;
/* coeffs[b0, b1, b2, a1, a2] */
switch(mode){
case ZOELZER_LOWPASS_FILTER_MODE:
norm = 1 / (1 + K / Q + K * K);
coeffs[0] = K * K * norm;
coeffs[1] = 2 * coeffs[0];
coeffs[2] = coeffs[0];
coeffs[3] = 2 * (K * K - 1) * norm;
coeffs[4] = (1 - K / Q + K * K) * norm;
break;
case ZOELZER_HIGHPASS_FILTER_MODE:
norm = 1 / (1 + K / Q + K * K);
coeffs[0] = 1 * norm;
coeffs[1] = -2 * coeffs[0];
coeffs[2] = coeffs[0];
coeffs[3] = 2 * (K * K - 1) * norm;
coeffs[4] = (1 - K / Q + K * K) * norm;
break;
case ZOELZER_BANDPASS_FILTER_MODE:
norm = 1 / (1 + K / Q + K * K);
coeffs[0] = K / Q * norm;
coeffs[1] = 0;
coeffs[2] = -coeffs[0];
coeffs[3] = 2 * (K * K - 1) * norm;
coeffs[4] = (1 - K / Q + K * K) * norm;
break;
case ZOELZER_NOTCH_FILTER_MODE:
norm = 1 / (1 + K / Q + K * K);
coeffs[0] = (1 + K * K) * norm;
coeffs[1] = 2 * (K * K - 1) * norm;
coeffs[2] = coeffs[0];
coeffs[3] = coeffs[1];
coeffs[4] = (1 - K / Q + K * K) * norm;
break;
case ZOELZER_PEAK_FILTER_MODE:
if (gain >= 0.5) {
norm = 1 / (1 + 1/Q * K + K * K);
coeffs[0] = (1 + V/Q * K + K * K) * norm;
coeffs[1] = 2 * (K * K - 1) * norm;
coeffs[2] = (1 - V/Q * K + K * K) * norm;
coeffs[3] = coeffs[1];
coeffs[4] = (1 - 1/Q * K + K * K) * norm;
}
else {
norm = 1 / (1 + V/Q * K + K * K);
coeffs[0] = (1 + 1/Q * K + K * K) * norm;
coeffs[1] = 2 * (K * K - 1) * norm;
coeffs[2] = (1 - 1/Q * K + K * K) * norm;
coeffs[3] = coeffs[1];
coeffs[4] = (1 - V/Q * K + K * K) * norm;
}
break;
case ZOELZER_LOWSHELF_FILTER_MODE:
if (gain >= 0.5) {
norm = 1 / (1 + M_SQRT2 * K + K * K);
coeffs[0] = (1 + sqrt(2*V) * K + V * K * K) * norm;
coeffs[1] = 2 * (V * K * K - 1) * norm;
coeffs[2] = (1 - sqrt(2*V) * K + V * K * K) * norm;
coeffs[3] = 2 * (K * K - 1) * norm;
coeffs[4] = (1 - M_SQRT2 * K + K * K) * norm;
} else {
norm = 1 / (1 + sqrt(2*V) * K + V * K * K);
coeffs[0] = (1 + M_SQRT2 * K + K * K) * norm;
coeffs[1] = 2 * (K * K - 1) * norm;
coeffs[2] = (1 - M_SQRT2 * K + K * K) * norm;
coeffs[3] = 2 * (V * K * K - 1) * norm;
coeffs[4] = (1 - sqrt(2*V) * K + V * K * K) * norm;
}
break;
case ZOELZER_HIGHSHELF_FILTER_MODE:
if (gain >= 0.5) {
norm = 1 / (1 + M_SQRT2 * K + K * K);
coeffs[0] = (V + sqrt(2*V) * K + K * K) * norm;
coeffs[1] = 2 * (K * K - V) * norm;
coeffs[2] = (V - sqrt(2*V) * K + K * K) * norm;
coeffs[3] = 2 * (K * K - 1) * norm;
coeffs[4] = (1 - M_SQRT2 * K + K * K) * norm;
} else {
norm = 1 / (V + sqrt(2*V) * K + K * K);
coeffs[0] = (1 + M_SQRT2 * K + K * K) * norm;
coeffs[1] = 2 * (K * K - 1) * norm;
coeffs[2] = (1 - M_SQRT2 * K + K * K) * norm;
coeffs[3] = 2 * (K * K - V) * norm;
coeffs[4] = (V - sqrt(2*V) * K + K * K) * norm;
}
break;
}
int size = buffer.getSize();
float* samples = buffer.getSamples(0);
float buf[size];
previous.process(samples, buf, size);
previous.setCoefficents(coeffs);
filter.setCoefficents(coeffs);
filter.process(samples, size);
for(int i=0; i<size; ++i){
float xfade = (float)i/(float)size;
samples[i] = buf[i]*(1.0f-xfade) + samples[i]*xfade;
}
}