// Update chart of frequency domain
private void UpdateSpectra()
{
var fftSize = int.Parse(fftSizeTextBox.Text);
var cepstrumSize = int.Parse(cepstrumSizeTextBox.Text);
_hopSize = int.Parse(hopSizeTextBox.Text);
if (fftSize != _fftSize)
{
_fftSize = fftSize;
_fft = new Fft(fftSize);
_cepstralTransform = new CepstralTransform(cepstrumSize, _fftSize);
}
if (cepstrumSize != _cepstrumSize)
{
_cepstrumSize = cepstrumSize;
_cepstralTransform = new CepstralTransform(_cepstrumSize, _fftSize);
}
var pos = _hopSize * _specNo;
var block = _signal[pos, pos + _fftSize];
block.ApplyWindow(WindowTypes.Hamming);
var cepstrum = _cepstralTransform.Direct(block);
var real = new float[_fftSize];
var imag = new float[_fftSize];
for (var i = 0; i < 32; i++)
{
real[i] = cepstrum[i];
}
_fft.Direct(real, imag);
var spectrum = _fft.PowerSpectrum(block, normalize: false).Samples;
var avg = spectrum.Average(s => LevelScale.ToDecibel(s));
var spectrumEstimate = real.Take(_fftSize / 2 + 1)
.Select(s => (float)LevelScale.FromDecibel(s * 40 / _fftSize - avg))
.ToArray();
spectrumPanel.Line = spectrum;
spectrumPanel.Markline = spectrumEstimate;
spectrumPanel.ToDecibel();
spectrumPanel.max_freq_value = spectrum.Length * _signal.SamplingRate / fftSize;
}
public void TestComplexCepstrum()
{
var output = new float[8];
_ct.Direct(_input, output);
Assert.That(output, Is.EqualTo(new[] { 5.34123949e+00, -6.07112628e-02, -3.81738790e-02, 1.43294733e-01,
6.28384672e-03, 1.79680255e-03, -5.12632421e-03, 7.09771400e-03 }).Within(1e-5));
}
private void UpdateSpectrumAndCepstrum()
{
var fftSize = int.Parse(fftSizeTextBox.Text);
var cepstrumSize = int.Parse(cepstrumSizeTextBox.Text);
_hopSize = int.Parse(hopSizeTextBox.Text);
if (fftSize != _fftSize)
{
_fftSize = fftSize;
_fft = new RealFft(fftSize);
_cepstralTransform = new CepstralTransform(cepstrumSize, _fftSize);
}
if (cepstrumSize != _cepstrumSize)
{
_cepstrumSize = cepstrumSize;
_cepstralTransform = new CepstralTransform(_cepstrumSize, _fftSize);
}
var pos = _hopSize * _specNo;
var block = _signal[pos, pos + _fftSize];
//block.ApplyWindow(WindowTypes.Hamming);
var cepstrum = _cepstralTransform.Direct(block);
var pitch = Pitch.FromCepstrum(block);
// ************************************************************************
// just visualize spectrum estimated from cepstral coefficients:
// ************************************************************************
var real = new float[_fftSize];
var imag = new float[_fftSize];
for (var i = 0; i < 32; i++)
{
real[i] = cepstrum[i];
}
_fft.Direct(real, real, imag);
var spectrum = _fft.PowerSpectrum(block, normalize: false).Samples;
var avg = spectrum.Average(s => LevelScale.ToDecibel(s));
var spectrumEstimate = real.Take(_fftSize / 2 + 1)
.Select(s => (float)LevelScale.FromDecibel(s * 40 / _fftSize - avg))
.ToArray();
spectrumPanel.Line = spectrum;
spectrumPanel.Markline = spectrumEstimate;
spectrumPanel.ToDecibel();
cepstrumPanel.Line = cepstrum.Samples;
cepstrumPanel.Mark = (int)(_signal.SamplingRate / pitch);
}
public void TestInverseComplexCepstrum()
{
var ct = new CepstralTransform(8);
var input = new[] { 1, 7, 2, 100, 59, 32, 11, 72f };
var output = new float[8];
var cepstrum = new float[8];
var d = ct.Direct(input, output);
ct.Inverse(output, cepstrum, d);
Assert.That(cepstrum, Is.EqualTo(input).Within(1e-4));
}
/// <summary>
/// Pitch estimation from signal cepstrum
/// </summary>
/// <param name="signal"></param>
/// <param name="low"></param>
/// <param name="high"></param>
/// <returns></returns>
public static float FromCepstrum(DiscreteSignal signal,
int startPos = 0,
int endPos = -1,
float low = 80,
float high = 400,
int cepstrumSize = 256,
int fftSize = 512)
{
var samplingRate = signal.SamplingRate;
if (endPos == -1)
{
endPos = signal.Length;
}
if (startPos != 0 || endPos != signal.Length)
{
signal = signal[startPos, endPos];
}
var pitch1 = (int)(1.0 * samplingRate / high); // 2,5 ms = 400Hz
var pitch2 = Math.Min(cepstrumSize - 1, (int)(1.0 * samplingRate / low)); // 12,5 ms = 80Hz
var cepstralTransform = new CepstralTransform(cepstrumSize, fftSize);
var cepstrum = cepstralTransform.Direct(signal);
var max = cepstrum[pitch1];
var peakIndex = pitch1;
for (var k = pitch1 + 1; k <= pitch2; k++)
{
if (cepstrum[k] > max)
{
max = cepstrum[k];
peakIndex = k;
}
}
return((float)samplingRate / peakIndex);
}
