EFFECT_RESONANT_LOWPASS::EFFECT_RESONANT_LOWPASS (CHAIN_OPERATOR::parameter_t co, CHAIN_OPERATOR::parameter_t
res, CHAIN_OPERATOR::parameter_t g)
: ProtoCoef(2), Coef(2)
{
cutoff = co;
Q = res;
gain_orig = gain = g;
laskuri = 0.0;
pi = 4.0 * atan(1.0);
// ---
// Setup filter s-domain coefficients
// ---
ProtoCoef[0].a0 = 1.0;
ProtoCoef[0].a1 = 0;
ProtoCoef[0].a2 = 0;
ProtoCoef[0].b0 = 1.0;
ProtoCoef[0].b1 = 0.765367 / Q; // Divide by resonance or Q
ProtoCoef[0].b2 = 1.0;
ProtoCoef[1].a0 = 1.0;
ProtoCoef[1].a1 = 0;
ProtoCoef[1].a2 = 0;
ProtoCoef[1].b0 = 1.0;
ProtoCoef[1].b1 = 1.847759 / Q; // Divide by resonance or Q
ProtoCoef[1].b2 = 1.0;
szxform(0);
szxform(1);
}
static void initFilter(float fs, float fc, float *icoeff, float Q) {
float *coef;
double a0, a1, a2, b0, b1, b2;
double k = 1.5; // Set overall filter gain factor
coef = icoeff + 1; // Skip k, or gain
// Section 1
a0 = 1.0;
a1 = 0;
a2 = 0;
b0 = 1.0;
b1 = 0.765367 / Q; // Divide by resonance or Q
b2 = 1.0;
szxform(&a0, &a1, &a2, &b0, &b1, &b2, fc, fs, &k, coef);
coef += 4; // Point to next filter section
// Section 2
a0 = 1.0;
a1 = 0;
a2 = 0;
b0 = 1.0;
b1 = 1.847759 / Q;
b2 = 1.0;
szxform(&a0, &a1, &a2, &b0, &b1, &b2, fc, fs, &k, coef);
icoeff[0] = (float)k;
}
void calcCoeff()
{
/*
* Compute z-domain coefficients for each biquad section
* for new Cutoff Frequency and Resonance
*/
unsigned nInd;
double a0, a1, a2, b0, b1, b2;
k = 1.0;
coef = iir.coef + 1; /* Skip k, or gain */
for (nInd = 0; nInd < iir.length; nInd++)
{
a0 = ProtoCoef[nInd].a0;
a1 = ProtoCoef[nInd].a1;
a2 = ProtoCoef[nInd].a2;
b0 = ProtoCoef[nInd].b0;
b1 = ProtoCoef[nInd].b1 / Q; /* Divide by resonance or Q */
b2 = ProtoCoef[nInd].b2;
szxform(&a0, &a1, &a2, &b0, &b1, &b2, fc, fs, &k, coef);
coef += 4; /* Point to next filter section */
}
/* Update overall filter gain in coef array */
iir.coef[0] = k;
}
void Filter::GetOutput(int V, Sample &data)
{
float Cutoff;
float Resonance;
if (m_FilterBypass || fc<0) return;
for (int n=0; n<data.GetLength(); n++)
{
coef = iir[V].coef + 1; /* Skip k, or gain */
k=0.25;
Cutoff = fc;
Resonance = Q;
Cutoff/=2;
if (Resonance>MAX_RES) Resonance=MAX_RES;
if (Cutoff>MAX_CUTOFF) Cutoff=MAX_CUTOFF;
if (Resonance<MIN_RES) Resonance=MIN_RES;
if (Cutoff<MIN_CUTOFF) Cutoff=MIN_CUTOFF;
if (n%10==0)
{
// if different from last time
//if (m_LastQ!=Q || m_LastFC!=fc)
{
for (nInd = 0; nInd < iir[V].length; nInd++)
{
a2 = ProtoCoef[nInd].a2;
a0 = ProtoCoef[nInd].a0;
a1 = ProtoCoef[nInd].a1;
b0 = ProtoCoef[nInd].b0;
b1 = ProtoCoef[nInd].b1 / Resonance;
b2 = ProtoCoef[nInd].b2;
szxform(&a0, &a1, &a2, &b0, &b1, &b2, Cutoff*(Cutoff/1000.0f), fs, &k, coef);
coef += 4;
}
iir[V].coef[0] = k;
m_LastQ=Q;
m_LastFC=fc;
}
}
data.Set(n,iir_filter(data[n],&iir[V]));
}
}
void EFFECT_RESONANT_LOWPASS::refresh_values(void)
{
if (cutoff == 0.0) cutoff = 0.1;
gain = gain_orig;
// ProtoCoef[0].a0 = 1.0;
ProtoCoef[0].a1 = 0;
ProtoCoef[0].a2 = 0;
// ProtoCoef[0].b0 = 1.0;
ProtoCoef[0].b1 = 0.765367 / Q; // Divide by resonance or Q
ProtoCoef[0].b2 = 1.0;
// ProtoCoef[1].a0 = 1.0;
ProtoCoef[1].a1 = 0;
ProtoCoef[1].a2 = 0;
// ProtoCoef[1].b0 = 1.0;
ProtoCoef[1].b1 = 1.847759 / Q; // Divide by resonance or Q
ProtoCoef[1].b2 = 1.0;
szxform(0);
szxform(1);
}
void LPF::update(int nframes){
unsigned int j;
float *hist1_ptr,*hist2_ptr,*coef_ptr;
float output,new_hist,history1,history2;
/* allocate history array if different size than last call */
if(!iir.history) {
iir.history = (float *) calloc(2*iir.length,sizeof(float));
if(!iir.history)
throw Exception("Unable to allocate history array in LPF");
}
float *in = ins[0];
float *qmods = ins[1]?ins[1]:floatZeroes;
float *fmods = ins[2]?ins[2]:floatZeroes;
q2=q+qmod*qmods[0];
fc2=fc+fmod*fmods[0];
///////////// INIT /////////////////////
float *coef = iir.coef + 1; /* Skip k, or gain */
extern float samprate;
double fs= samprate;
double k = gain;
for(unsigned int i=0;i<iir.length;i++){
double a0 = protoCoef[i].a0;
double a1 = protoCoef[i].a1;
double a2 = protoCoef[i].a2;
double b0 = protoCoef[i].b0;
double b1 = protoCoef[i].b1/q2;
double b2 = protoCoef[i].b2;
szxform(&a0, &a1, &a2, &b0, &b1, &b2, fc2, fs, &k, coef);
coef+=4;
}
iir.coef[0]=k;
///////////// END OF FILTER INIT ////////
for(int i=0;i<nframes;i++){
float input = *in++;
coef_ptr = iir.coef; /* coefficient pointer */
hist1_ptr = iir.history; /* first history */
hist2_ptr = hist1_ptr + 1; /* next history */
/* 1st number of coefficients array is overall input scale factor,
* or filter gain */
output = input * (*coef_ptr++);
for(j = 0 ; j < iir.length; j++)
{
history1 = *hist1_ptr; /* history values */
history2 = *hist2_ptr;
output = output - history1 * (*coef_ptr++);
new_hist = output - history2 * (*coef_ptr++); /* poles */
output = new_hist + history1 * (*coef_ptr++);
output = output + history2 * (*coef_ptr++); /* zeros */
*hist2_ptr++ = *hist1_ptr;
*hist1_ptr++ = new_hist;
hist1_ptr++;
hist2_ptr++;
}
out[i]=output;
}
}
