double WbGammaTone(double x,double tdres,double centerfreq, int n, double tau,double gain,int order)
{
static double wbphase;
static COMPLEX wbgtf[4], wbgtfl[4];
double delta_phase,dtmp,c1LP,c2LP,out;
int i,j;
if (n==0)
{
wbphase = 0;
for(i=0; i<=order;i++)
{
wbgtfl[i] = compmult(0,compexp(0));
wbgtf[i] = compmult(0,compexp(0));
}
}
delta_phase = -TWOPI*centerfreq*tdres;
wbphase += delta_phase;
dtmp = tau*2.0/tdres;
c1LP = (dtmp-1)/(dtmp+1);
c2LP = 1.0/(dtmp+1);
wbgtf[0] = compmult(x,compexp(wbphase)); /* FREQUENCY SHIFT */
for(j = 1; j <= order; j++) /* IIR Bilinear transformation LPF */
wbgtf[j] = comp2sum(compmult(c2LP*gain,comp2sum(wbgtf[j-1],wbgtfl[j-1])),
compmult(c1LP,wbgtfl[j]));
out = REAL(compprod(compexp(-wbphase), wbgtf[order])); /* FREQ SHIFT BACK UP */
for(i=0; i<=order;i++) wbgtfl[i] = wbgtf[i];
return(out);
}
/**
Pass the signal through the gammatone filter\\
1. shift the signal by centeral frequency of the gamma tone filter\\
2. low pass the shifted signal \\
3. shift back the signal \\
4. take the real part of the signal as output
@author Xuedong Zhang
*/
double TGammaTone::run(double x)
{
x = gain*x;
phase += delta_phase;
gtf[0] = compmult(x,compexp(phase)); // FREQUENCY SHIFT
for(int j = 1; j <= gtf_order; j++) // IIR Bilinear transformation LPF
gtf[j] = comp2sum(compmult(c2LP,comp2sum(gtf[j-1],gtfl[j-1])),
compmult(c1LP,gtfl[j]));
double out = REAL(compprod(compexp(-phase), gtf[gtf_order])); // FREQ SHIFT BACK UP
for(int i=0; i<=gtf_order;i++) gtfl[i] = gtf[i];
return(out);
};
void TransMult(double *rdatacoeffs, double *idatacoeffs,
double *rfiltercoeffs, double *ifiltercoeffs,
double *rres, double *ires,
int bw)
{
int m, l, size;
double *rdptr, *idptr, *rrptr, *irptr;
size = 2*bw ;
rdptr = rdatacoeffs;
idptr = idatacoeffs;
rrptr = rres;
irptr = ires;
for (m=0; m<bw; m++) {
for (l=m; l<bw; l++) {
compmult(rfiltercoeffs[l], ifiltercoeffs[l],
rdptr[l-m], idptr[l-m],
rrptr[l-m], irptr[l-m]);
rrptr[l-m] *= sqrt(4*M_PI/(2*l+1));
irptr[l-m] *= sqrt(4*M_PI/(2*l+1));
}
rdptr += bw-m; idptr += bw-m;
rrptr += bw-m; irptr += bw-m;
}
for (m=bw+1; m<size; m++) {
for (l=size-m; l<bw; l++){
compmult(rfiltercoeffs[l], ifiltercoeffs[l],
rdptr[l-size+m], idptr[l-size+m],
rrptr[l-size+m], irptr[l-size+m]);
rrptr[l-size+m] *= sqrt(4*M_PI/(2*l+1));
irptr[l-size+m] *= sqrt(4*M_PI/(2*l+1));
}
rdptr += m-bw; idptr += m-bw;
rrptr += m-bw; irptr += m-bw;
}
}
