private const int numberWaveletTransforms = 2; // number of wavelet transform iterations, 3?
/// <summary>
/// Create a Mfcc object
/// This method is not optimized in the sense that the Mel Filter Bands
/// and the DCT is created here (and not read in)
/// Only support an overlap of half the window size
/// </summary>
/// <param name="winsize">window size</param>
/// <param name="srate">sample rate</param>
/// <param name="numberFilters">number of filters (MEL COEFFICIENTS). E.g. 36 (SPHINX-III uses 40)</param>
/// <param name="numberCoefficients">number of MFCC COEFFICIENTS. E.g. 20</param>
public MFCC(int winsize, int srate, int numberFilters, int numberCoefficients)
{
this.numberCoefficients = numberCoefficients;
// Compute the Mel Frequencey Filters
var melFilter = new MelFilter(winsize, srate, numberFilters, 20);
this.melScaleFreqsIndex = melFilter.MelScaleFreqsIndex;
this.melScaleTriangleHeights = melFilter.MelScaleTriangleHeights;
this.filterWeights = melFilter.FilterWeights;
// Compute the DCT
dct = new DctMatrix(numberCoefficients, numberFilters).Matrix;
#if DEBUG
// dct.WriteAscii("dct-mirage-orig.ascii");
// dct.DrawMatrixGraph("dct-mirage-orig.png");
#endif
}
public void TestMelFrequencyFiltering()
{
var audio = BassProxy.Instance;
//const string fileName = @"Tests\Passacaglia, Handel-Saw-86bmp.wav";
const string fileName = @"Tests\Passacaglia, Handel-Sine-86bmp.wav";
const int sampleRate = 44100;
const int fftWindowsSize = 2048;
const int fftOverlap = 1024;
const bool colorize = true;
const int melFilters = 120;
var monoSignal = BassProxy.ReadMonoFromFile(fileName, sampleRate);
double[][] specNormal = FFTUtils.CreateSpectrogramLomont(monoSignal, fftWindowsSize, fftOverlap);
var specNormalMat = new Matrix(specNormal).Transpose();
specNormalMat.DrawMatrixImage("spec_normal.png", -1, -1, colorize, true);
// Mel Scale Filterbank
// Mel-frequency is proportional to the logarithm of the linear frequency,
// reflecting similar effects in the human's subjective aural perception)
var melFilter = new MelFilter(fftWindowsSize, sampleRate, melFilters, 0);
var specNormalMelMat = melFilter.FilterWeights * specNormalMat;
specNormalMelMat.DrawMatrixImage("spec_normal_mel.png", -1, -1, colorize, true);
melFilter.FilterWeights.WriteCSV("melfilter_orig.csv");
melFilter.FilterWeights.DrawMatrixGraph("melfilter_orig.png");
var melFilterBank = new MelFilterBank(0, sampleRate / 2, melFilters, fftOverlap, sampleRate);
var melFilterBankMat = melFilterBank.Matrix;
melFilterBankMat.WriteCSV("melfilter_new.csv");
melFilterBankMat.DrawMatrixGraph("melfilter_new.png");
var specNormalMelMatNew = melFilterBankMat * specNormalMat;
specNormalMelMatNew.DrawMatrixImage("spec_normal_mel_new.png", -1, -1, colorize, true);
}
