private TKomplex kdiff(TKomplex a, TKomplex b)
{
res.real = a.real - b.real;
res.imag = a.imag - b.imag;
return (res);
}
private void Initialize(Sample currentSample)
{
N = currentSample.Limit;
x = new TKomplex[N + 1];
y = new TKomplex[N + 1];
we = new TKomplex[N / 2];
for (int i = 0; i < (N / 2); i++) // Init look up table for sine and cosine values
{
we[i].real = Math.Cos(2 * Math.PI * (double)(i) / (double)(N));
we[i].imag = Math.Sin(2 * Math.PI * (double)(i) / (double)(N));
}
var windowedSignal = BuildHanWindow(currentSample);
for (int i = 0; i < currentSample.Limit; i++)
{
y[i].real = windowedSignal[i];
y[i].imag = 0;
}
}
private void Initialize(Sample currentSample)
{
N = currentSample.Limit;
x = new TKomplex[N + 1];
y = new TKomplex[N + 1];
we = new TKomplex[N / 2];
for (int i = 0; i < (N / 2); i++) // Init look up table for sine and cosine values
{
we[i].real = Math.Cos(2 * Math.PI * (double)(i) / (double)(N));
we[i].imag = Math.Sin(2 * Math.PI * (double)(i) / (double)(N));
}
var windowedSignal = BuildHanWindow(currentSample);
for (int i = 0; i < currentSample.Limit; i++)
{
y[i].real = windowedSignal[i];
y[i].imag = 0;
}
}
private TKomplex kprod(TKomplex a, TKomplex b)
{
res.real = a.real * b.real - a.imag * b.imag;
res.imag = a.real * b.imag + a.imag * b.real;
return(res);
}
private TKomplex kdiff(TKomplex a, TKomplex b)
{
res.real = a.real - b.real;
res.imag = a.imag - b.imag;
return(res);
}
private TKomplex ksum(TKomplex a, TKomplex b)
{
res.real = a.real + b.real;
res.imag = a.imag + b.imag;
return(res);
}
private TKomplex kprod(TKomplex a, TKomplex b)
{
res.real = a.real * b.real - a.imag * b.imag;
res.imag = a.real * b.imag + a.imag * b.real;
return (res);
}
private TKomplex ksum(TKomplex a, TKomplex b)
{
res.real = a.real + b.real;
res.imag = a.imag + b.imag;
return (res);
}
private void CalcSubFFT(TKomplex[] a, int n)
{
int i, k, m;
TKomplex w;
TKomplex v;
TKomplex h;
k = 1;
while (k <= n / 2)
{
m = 0;
while (m <= (n - 2 * k))
{
for (i = m; i < m + k; i++)
{
// sine and cosine values from look up table
w.real = we[((i - m) * N / k / 2)].real;
w.imag = we[((i - m) * N / k / 2)].imag;
// classic calculation of sine and cosine values
//w.real = Math.Cos( Math.PI * (double)(i-m) / (double)(k));
//w.imag = Math.Sin( Math.PI * (double)(i-m) / (double)(k));
h = kprod(a[i + k], w);
v = a[i];
a[i] = ksum(a[i], h);
a[i + k] = kdiff(v, h);
}
m = m + 2 * k;
}
k = k * 2;
}
}
private void BitInvert(TKomplex[] a, int n)
{ // invert bits for each index. n is number of samples and a the array of the samples
int i, mv = n / 2;
int k, rev = 0;
TKomplex b;
for (i = 1; i < n; i++) // run tru all the indexes from 1 to n
{
k = i;
mv = n / 2;
rev = 0;
while (k > 0) // invert the actual index
{
if ((k % 2) > 0)
rev = rev + mv;
k = k / 2;
mv = mv / 2;
}
{ // switch the actual sample and the bitinverted one
if (i < rev)
{
b = a[rev];
a[rev] = a[i];
a[i] = b;
}
}
}
}
