public boolean validFreq(float f) {
if (f < 60) {
Minim.error("This filter quickly becomes unstable below 60 Hz, setting frequency to 60 Hz.");
return false;
}
return true;
}
/**
* Performs a forward transform on the passed buffers.
*
* @param buffReal the real part of the time domain signal to transform
* @param buffImag the imaginary part of the time domain signal to transform
*/
public void forward(float[] buffReal, float[] buffImag) {
if (buffReal.length != timeSize || buffImag.length != timeSize) {
Minim.error("FFT.forward: The length of the passed buffers must be equal to timeSize().");
return;
}
setComplex(buffReal, buffImag);
bitReverseComplex();
fft();
fillSpectrum();
}
@Override
public void forward(float[] buffer) {
if (buffer.length != timeSize) {
Minim.error(
"FFT.forward: The length of the passed sample buffer " + "must be equal to timeSize().");
return;
}
doWindow(buffer);
// copy samples to real/imag in bit-reversed order
bitReverseSamples(buffer);
// perform the fft
fft();
// fill the spectrum buffer with amplitudes
fillSpectrum();
}
@Override
public void inverse(float[] buffer) {
if (buffer.length > real.length) {
Minim.error("FFT.inverse: the passed array's length must equal FFT.timeSize().");
return;
}
// conjugate
for (int i = 0; i < timeSize; i++) {
imag[i] *= -1;
}
bitReverseComplex();
fft();
// copy the result in real into buffer, scaling as we do
for (int i = 0; i < buffer.length; i++) {
buffer[i] = real[i] / real.length;
}
}
@Override
public void scaleBand(int i, float s) {
if (s < 0) {
Minim.error("Can't scale a frequency band by a negative value.");
return;
}
if (spectrum[i] != 0) {
real[i] /= spectrum[i];
imag[i] /= spectrum[i];
spectrum[i] *= s;
real[i] *= spectrum[i];
imag[i] *= spectrum[i];
}
if (i != 0 && i != timeSize / 2) {
real[timeSize - i] = real[i];
imag[timeSize - i] = -imag[i];
}
}
@Override
public void setBand(int i, float a) {
if (a < 0) {
Minim.error("Can't set a frequency band to a negative value.");
return;
}
if (real[i] == 0 && imag[i] == 0) {
real[i] = a;
spectrum[i] = a;
} else {
real[i] /= spectrum[i];
imag[i] /= spectrum[i];
spectrum[i] = a;
real[i] *= spectrum[i];
imag[i] *= spectrum[i];
}
if (i != 0 && i != timeSize / 2) {
real[timeSize - i] = real[i];
imag[timeSize - i] = -imag[i];
}
}
