public override void ProcessSignal(float[] signal, float freqSampling)
{
var coeff = new BandPassButtersworthCoefficients(FilterOrder, freqSampling, MinCornerFrequency,
MaxCornerFrequency);
var chain = coeff.Calculate();
// in place filtering
if (ZeroPhase)
{
chain.Filter(signal, 0, signal, 0, signal.Length);
}
else
{
chain.FilterOnce(signal, 0, signal, 0, signal.Length);
}
}
public void TestBandPassSinusoid()
{
const int order = 16;
const int fs = 44100;
const int targetFrequency = 3;
const double br = 5;
const int cycles = 10;
double[] frequencies =
{ 65.406, 130.81, 261.63, 523.25, 1046.5, 2093.0, 4186.0, 8372.0 };
var signal = new double[cycles * fs];
foreach (var frequency in frequencies)
{
Helpers.GenerateSinusoid(frequency, fs, signal);
}
var im = new double[signal.Length];
var coeff = new BandPassButtersworthCoefficients(order, fs, frequencies[targetFrequency] - br, frequencies[targetFrequency] + br);
var chain = coeff.Calculate();
chain.Filter(signal, 0, signal, 0, signal.Length);
var count = signal.Length / 2;
FourierTransform2.FFT(signal, im, FourierTransform.Direction.Forward);
Helpers.CalculateEnergy(signal, im, count);
var maxEnergy = signal.Take(count).Max();
var step = fs / (2d * count);
for (int i = 1; i < count - 1; i++)
{
var freq = i * step;
if (signal[i] > signal[i - 1] && signal[i] > signal[i + 1] && signal[i] >= 0.05 * maxEnergy)
{
var peak = frequencies.FirstOrDefault(x => Math.Abs(freq - x) <= 1);
Assert.AreEqual(frequencies[targetFrequency], peak);
}
}
}
public void TestBandPass16()
{
const int order = 16;
const double fs = 31250d;
const double cutoffFrequency = 60;
const double br = 1;
const double error = 1e-3;
var coeff = new BandPassButtersworthCoefficients(order, fs, cutoffFrequency - br, cutoffFrequency + br);
var chain = coeff.Calculate();
var expected = Helpers.LoadScript(Resources.BandPass16).Reverse().ToList();
var expectedGain = 7.114329431453330e-60;
Assert.AreEqual(expectedGain, chain.Gain, error);
Assert.AreEqual(expected.Count, chain.Count);
for (int i = 0; i < expected.Count; i++)
{
Helpers.ValidateBiquad(expected[i], chain[i], error);
}
}
public void TestBandPass12()
{
const int order = 12;
const double fs = 32000d;
const double cutoffFrequency = 1000d;
const double br = 10;
const double error = 1e-2;
var coeff = new BandPassButtersworthCoefficients(order, fs, cutoffFrequency - br, cutoffFrequency + br);
var chain = coeff.Calculate();
var expected = Helpers.LoadScript(Resources.BandPass12).Reverse().ToList();
var expectedGain = 2.883388964711794e-33;
Assert.AreEqual(expectedGain, chain.Gain, error);
Assert.AreEqual(expected.Count, chain.Count);
for (int i = 0; i < expected.Count; i++)
{
Helpers.ValidateBiquad(expected[i], chain[i], error);
}
}
public void TestBandPass08()
{
const int order = 8;
const double fs = 44100d;
const double cutoffFrequency = 500d;
const double br = 5;
const double error = 1e-3;
var coeff = new BandPassButtersworthCoefficients(order, fs, cutoffFrequency - br, cutoffFrequency + br);
var chain = coeff.Calculate();
var expected = Helpers.LoadScript(Resources.BandPass08).Reverse().ToList();
var expectedGain = 6.541867072214145e-26;
Assert.AreEqual(expectedGain, chain.Gain, error);
Assert.AreEqual(expected.Count, chain.Count);
for (int i = 0; i < expected.Count; i++)
{
Helpers.ValidateBiquad(expected[i], chain[i], error);
}
}
