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 = new float[_fftSize];
_cepstralTransform.RealCepstrum(block.Samples, cepstrum);
// ************************************************************************
// 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 - avg))
.ToArray();
spectrumPanel.Line = spectrum;
spectrumPanel.Markline = spectrumEstimate;
spectrumPanel.ToDecibel();
var pitch = Pitch.FromCepstrum(block);
cepstrumPanel.Line = cepstrum;
cepstrumPanel.Mark = (int)(_signal.SamplingRate / pitch);
}
