public static Complex[] padded_FFT(ref double[] @in)
{
Debug.Assert(@in.Length > 0);
int n = @in.Length;
int padded = n > 256 ? Util.NextLowPrimes(n) : n;
Array.Resize <double>(ref @in, padded);
// 4096 real numbers on input processed by FFTW dft_r2c_1d transform gives
// 4096/2+1 = 2049 complex numbers at output
// prepare the input arrays
var fftwInput = new FFTW.DoubleArray(@in);
int complexSize = (padded >> 1) + 1; // this is the same as (padded / 2 + 1);
var fftwOutput = new FFTW.ComplexArray(complexSize);
FFTW.ForwardTransform(fftwInput, fftwOutput);
Array.Resize <double>(ref @in, n);
// free up memory
GC.Collect();
return(FFTUtils.ComplexDoubleToComplex(fftwOutput.ComplexValues));
}
private double[] MagnitudeSpectrum(float[] frame)
{
// prepare the input arrays
FFTW.DoubleArray fftwInput = new FFTW.DoubleArray(MathUtils.FloatToDouble(frame));
int complexSize = (frame.Length >> 1) + 1;
FFTW.ComplexArray fftwOutput = new FFTW.ComplexArray(complexSize);
FFTW.ForwardTransform(fftwInput, fftwOutput);
double[] magSpectrum = fftwOutput.Abs;
/*
* double[] magSpectrum = new double[frame.Length];
*
* // calculate FFT for current frame
* fft.ComputeFFT(frame);
*
* // System.err.println("FFT SUCCEED");
* // calculate magnitude spectrum
* for (int k = 0; k < frame.Length; k++)
* {
* magSpectrum[k] = Math.Sqrt(fft.real[k] * fft.real[k] + fft.imag[k] * fft.imag[k]);
* }
*/
return(magSpectrum);
}
