musicdsp.org source code archive - WSInf

int i;
double *h1 = new double[N];
double *h2 = new double[N];
// 1. Generate lowpass filter at first (low) cutoff frequency
wsfirLP(h1, N, WINDOW, fc1);
// 2. Generate highpass filter at second (high) cutoff frequency
wsfirHP(h2, N, WINDOW, fc2);
// 3. Add the 2 filters together
for (i = 0; i < N; i++) {
h[i] = h1[i] + h2[i];
}
// Delete dynamic memory
delete []h1;
delete []h2;
return;
}
// Generate bandpass filter
//
// This is done by generating a bandstop filter and spectrally inverting it
void wsfirBP(double h[],// h[] will be written with the filter taps
const int &N,// size of the filter
const int &WINDOW,// window function (W_BLACKMAN, W_HANNING, etc.)
const double &fc1,// low cutoff frequency
const double &fc2)// high cutoff frequency
{
int i;
// 1. Generate bandstop filter
wsfirBS(h, N, WINDOW, fc1, fc2);
// 2. Spectrally invert bandstop (negate all, and add 1 to center sample)
for (i = 0; i < N; i++) {
h[i] *= -1.0;// = 0 - h[i]
}
h[(N-1)/2] += 1.0;// = 1 - h[(N-1)/2]
return;
}
// Generate sinc function - used for making lowpass filter
void genSinc(double sinc[],// sinc[] will be written with the sinc function
const int &N,// size (number of taps)
const double &fc)// cutoff frequency
{
int i;
const double M = N-1;
double n;
// Constants
const double PI = 3.14159265358979323846;
// Generate sinc delayed by (N-1)/2
for (i = 0; i < N; i++) {
if (i == M/2.0) {
sinc[i] = 2.0 * fc;
}
else {
n = (double)i - M/2.0;
sinc[i] = sin(2.0*PI*fc*n) / (PI*n);
}
}
return;
}
// Generate window function (Blackman)
void wBlackman(double w[],// w[] will be written with the Blackman window
const int &N)// size of the window
{
int i;
const double M = N-1;
const double PI = 3.14159265358979323846;
for (i = 0; i < N; i++) {
w[i] = 0.42 - (0.5 * cos(2.0*PI*(double)i/M)) + (0.08*cos(4.0*PI*(double)i/M));
}