67 lines
2.4 KiB
C#
67 lines
2.4 KiB
C#
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using System;
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namespace FftSharp
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{
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public static class Filter
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{
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/// <summary>
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/// Silence frequencies above the given frequency
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/// </summary>
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public static double[] LowPass(double[] values, double sampleRate, double maxFrequency) =>
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BandPass(values, sampleRate, double.NegativeInfinity, maxFrequency);
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/// <summary>
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/// Silence frequencies below the given frequency
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/// </summary>
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public static double[] HighPass(double[] values, double sampleRate, double minFrequency) =>
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BandPass(values, sampleRate, minFrequency, double.PositiveInfinity);
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/// <summary>
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/// Silence frequencies outside the given frequency range
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/// </summary>
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public static double[] BandPass(double[] values, double sampleRate, double minFrequency, double maxFrequency)
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{
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Complex[] fft = Transform.FFT(values);
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double[] fftFreqs = Transform.FFTfreq(sampleRate, fft.Length, oneSided: false);
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for (int i = 0; i < fft.Length; i++)
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{
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double freq = Math.Abs(fftFreqs[i]);
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if ((freq > maxFrequency) || (freq < minFrequency))
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{
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fft[i].Real = 0;
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fft[i].Imaginary = 0;
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}
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}
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return InverseReal(fft);
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}
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/// <summary>
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/// Silence frequencies inside the given frequency range
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/// </summary>
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public static double[] BandStop(double[] values, double sampleRate, double minFrequency, double maxFrequency)
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{
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Complex[] fft = Transform.FFT(values);
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double[] fftFreqs = Transform.FFTfreq(sampleRate, fft.Length, oneSided: false);
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for (int i = 0; i < fft.Length; i++)
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{
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double freq = Math.Abs(fftFreqs[i]);
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if ((freq <= maxFrequency) && (freq >= minFrequency))
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{
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fft[i].Real = 0;
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fft[i].Imaginary = 0;
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}
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}
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return InverseReal(fft);
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}
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private static double[] InverseReal(Complex[] fft)
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{
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Transform.IFFT(fft);
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double[] Filtered = new double[fft.Length];
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for (int i = 0; i < fft.Length; i++)
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Filtered[i] = fft[i].Real;
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return Filtered;
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}
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}
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}
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