public override void ProcessSignal(float[] signal, float freqSampling)
{
var coeff = new HighPassButtersworthCoefficients(FilterOrder, freqSampling, CutOffFrequency);
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 TestHighPassSinusoid()
{
const int order = 16;
const int fs = 44100;
const double cutoffFrequency = 700d;
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 HighPassButtersworthCoefficients(order, fs, cutoffFrequency);
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);
var peakSet = new HashSet <double>();
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] >= 0.001 * maxEnergy)
{
var peak = frequencies.FirstOrDefault(x => Math.Abs(freq - x) <= 1);
Assert.AreNotEqual(0, peak);
peakSet.Add(peak);
}
}
Assert.IsTrue(peakSet.SetEquals(frequencies.Where(x => x > cutoffFrequency)));
}
public void TestHighPass16()
{
const int order = 16;
const double fs = 31250d;
const double cutoffFrequency = 100d;
const double error = 1e-4;
var coeff = new HighPassButtersworthCoefficients(order, fs, cutoffFrequency);
var chain = coeff.Calculate();
var expected = Helpers.LoadScript(Resources.HighPass16).Reverse().ToList();
var expectedGain = 0.902520827102739;
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);
}
}