/*!
This can be used to create a new minimum phase bandlimited step function
to store for later use as a lookup table.
Note that BLEPOscillator.cpp already has a runtime constant version of a BLEP
for use with the BLEP-based oscillators.
*/
float *GenerateMinBLEP(int zeroCrossings, int overSampling)
{
int i, n, m;
float r, a, b;
float *buffer1, *buffer2, *minBLEP;
// use power-of-two for DFT/Cepstrum for potential future
// speed boost
n = (zeroCrossings * 2 * overSampling) + 1;
m = n-1;
buffer1 = new float[m];
buffer2 = new float[m];
// Generate Sinc
a = (float)-zeroCrossings;
b = (float)zeroCrossings;
for(i = 0; i < m; i++)
{
r = ((float)i) / ((float)m);
buffer1[i] = sinc(a + (r * (b - a)));
}
GenerateBlackmanWindow(m, buffer2);
for(i = 0; i < m; i++)
{
buffer1[i] *= buffer2[i];
}
// Minimum Phase Reconstruction
RealCepstrum(m, buffer1, buffer2);
MinimumPhase(m, buffer2, buffer1);
// Integrate Into MinBLEP
minBLEP = new float[n];
a = 0.0f;
for(i = 0; i < m; i++)
{
a += buffer1[i];
minBLEP[i] = a;
}
// copy next-to-last sample
minBLEP[m] = minBLEP[m-1];
// Normalize
a = minBLEP[m];
a = 1.0f / a;
for(i = 0; i < n; i++)
{
minBLEP[i] *= a;
}
delete buffer1;
delete buffer2;
return minBLEP;
}
// Generate MinBLEP And Return It In An Array Of Floating Point Values
float *GenerateMinBLEP(int zeroCrossings, int overSampling)
{
int i, n;
float r, a, b;
float *buffer1, *buffer2, *minBLEP;
n = (zeroCrossings * 2 * overSampling) + 1;
buffer1 = new float[n];
buffer2 = new float[n];
// Generate Sinc
a = (float)-zeroCrossings;
b = (float)zeroCrossings;
for(i = 0; i < n; i++)
{
r = ((float)i) / ((float)(n - 1));
buffer1[i] = SINC(a + (r * (b - a)));
}
// Window Sinc
BlackmanWindow(n, buffer2);
for(i = 0; i < n; i++)
buffer1[i] *= buffer2[i];
// Minimum Phase Reconstruction
RealCepstrum(n, buffer1, buffer2);
MinimumPhase(n, buffer2, buffer1);
// Integrate Into MinBLEP
minBLEP = new float[n];
a = 0.0f;
for(i = 0; i < n; i++)
{
a += buffer1[i];
minBLEP[i] = a;
}
// Normalize
a = minBLEP[n - 1];
a = 1.0f / a;
for(i = 0; i < n; i++)
minBLEP[i] *= a;
delete buffer1;
delete buffer2;
return minBLEP;
}
