public void ComputeInverseMatrixUsingLomontTableFFT(Matrix m, int column, ref double[] signal, int winsize, int overlap)
{
double[] spectrogramWindow = m.GetColumn(column);
// extend window with the inverse duplicate array
int len = spectrogramWindow.Length;
var extendedWindow = new double[len * 2];
Array.Copy(spectrogramWindow, extendedWindow, len);
for (int i = 1; i < len; i++)
{
extendedWindow[len + i] = spectrogramWindow[len - i];
}
double[] complexSignal = FFTUtils.DoubleToComplexDouble(extendedWindow);
lomonFFT.TableFFT(complexSignal, false);
double[] window = win.Window;
// multiply by window w/ overlap-add
int N = complexSignal.Length / 2;
var returnArray = new double[N];
for (int j = 0; j < N; j++)
{
double re = complexSignal[2 * j] / Math.Sqrt(winsize);
//double img = complexSignal[2*j + 1];
returnArray[j] = re * window[j]; // smooth yet another time (also did this when doing FFT)
// overlap-add method
// scale with 2 just because the volume got so much lower when using a second smoothing filter when reconstrcting
signal[j + overlap * column] = signal[j + overlap * column] + returnArray[j]; // * 3;
}
}
// seem to the be the fastest FFT?
static double[] FFTWLIB(double[] signal)
{
var complexSignal = FFTUtils.DoubleToComplexDouble(signal);
// prepare the input arrays
var complexInput = new fftw_complexarray(complexSignal);
var complexOutput = new fftw_complexarray(complexSignal.Length / 2);
fftw_plan fft = fftw_plan.dft_1d(complexSignal.Length / 2, complexInput, complexOutput, fftw_direction.Forward, fftw_flags.Estimate);
// perform the FFT
fft.Execute();
// get the result
var spectrum_fft_abs = complexOutput.Abs;
//Export.ExportCSV("audio_buffer_padded2.csv", signal);
//Export.ExportCSV("spectrum_fft_abs2.csv", spectrum_fft_abs2, fftSize);
// free up memory
complexInput = null;
complexOutput = null;
return(spectrum_fft_abs);
}
