public static void WhiteNoiseFilter(FFTs stft, double threshold, SelectedWindowIndices indices = null, bool dB = true)
{
List <Complex[]> data = stft.GetFFTs();
(int timeIndex1, int timeIndex2, int freqIndex1, int freqIndex2) =
indices != null?indices.Indices() : (0, data.Count, 0, stft.fftSize);
threshold = dB ? Math.Pow(10, threshold / 20) : threshold;
for (int n = timeIndex1; n < timeIndex2; n++)
{
for (int k = freqIndex1; k < freqIndex2; k++)
{
if (data[n][k].Magnitude < threshold)
{
data[n][k].Real = 0;
data[n][k].Imaginary = 0;
}
}
}
}
public static void AddGain(FFTs stft, double gain = 0, SelectedWindowIndices indices = null, bool dB = true)
{
(int timeIndex1, int timeIndex2, int freqIndex1, int freqIndex2) =
indices != null?indices.Indices() : (0, stft.Count, 0, stft.fftSize);
//Defaults to dB
//Converts to linear gain for multiplying gain to data
gain = dB ? Math.Pow(10, gain / 20) : gain;
List <Complex[]> data = stft.GetFFTs();
for (int n = timeIndex1; n < timeIndex2; n++)
{
for (int k = freqIndex1; k < freqIndex2; k++)
{
data[n][k].Real *= gain;
data[n][k].Imaginary *= gain;
}
}
}
private static void HighPassFilter(FFTs stft, double cutoff, SelectedWindowIndices indices = null)
{
(int timeIndex1, int timeIndex2, int freqIndex1, int freqIndex2) =
indices != null?indices.Indices() : (0, stft.Count, 0, stft.fftSize / 2);
List <Complex[]> data = stft.GetFFTs();
int index_cutoff = (int)(cutoff / stft.FreqResolution);
for (int n = timeIndex1; n < timeIndex2; n++)
{
for (int k = freqIndex1; k < freqIndex2; k++)
{
if (k <= index_cutoff)
{
data[n][k] = new Complex();
data[n][stft.fftSize - 1 - k] = new Complex(); //Mirrored side
}
}
}
}
public static void FrequencyShifter(FFTs stft, int freq_shift, SelectedWindowIndices indices = null, int order = 0, double thresh = 0.9)
{
int indexShift = freq_shift / stft.FreqResolution;
if (indexShift == 0)
{
return;
}
(int timeIndex1, int timeIndex2, int freqIndex1, int freqIndex2) =
indices != null?indices.Indices() : (0, stft.Count, 0, stft.fftSize);
//Shift map tells how far each index is going to shift
//Order of 0 results in a linear shifter
//shift_mod gives a scaling factor to each shifted index
int[] shift_map = createFreqShiftMap(stft, indexShift, indices, order, thresh);
double[] shift_mod = createFreqShiftModulation(stft, indexShift, indices);
List <Complex[]> ffts = stft.GetFFTs();
for (int n = timeIndex1; n < timeIndex2; n++)
{
Complex[] fft = ffts[n];
Complex[] shifted_fft = new Complex[fft.Length];
for (int k = 0; k < fft.Length; k++)
{
if (k + shift_map[k] >= 0 && k + shift_map[k] < fft.Length) //Ignore the ones that get shifted too far
{
shifted_fft[k + shift_map[k]] += fft[k] * shift_mod[k];
}
}
Array.Copy(shifted_fft, fft, fft.Length);
}
}