annotate dsp/mfcc/MFCC.cpp @ 298:255e431ae3d4

* Key detector: when returning key strengths, use the peak value of the
  three underlying chromagram correlations (from 36-bin chromagram)
  corresponding to each key, instead of the mean.
  Rationale: This is the same method as used when returning the key value,
  and it's nice to have the same results in both returned value and plot.
  The peak performed better than the sum with a simple test set of triads,
  so it seems reasonable to change the plot to match the key output rather
  than the other way around.

* FFT: kiss_fftr returns only the non-conjugate bins, synthesise the rest
  rather than leaving them (perhaps dangerously) undefined.  Fixes an
  uninitialised data error in chromagram that could cause garbage results
  from key detector.

* Constant Q: remove precalculated values again, I reckon they're not
  proving such a good tradeoff.

/* -*- c-basic-offset: 4 indent-tabs-mode: nil -*-  vi:set ts=8 sts=4 sw=4: */

/*
    QM DSP Library

    Centre for Digital Music, Queen Mary, University of London.
    This file copyright 2005 Nicolas Chetry, copyright 2008 QMUL.
    All rights reserved.
*/

#include <cmath>
#include <cstdlib>
#include <cstring>

#include "MFCC.h"
#include "dsp/transforms/FFT.h"
#include "base/Window.h"

MFCC::MFCC(MFCCConfig config)
{
    int i,j;

    /* Calculate at startup */
    double *freqs, *lower, *center, *upper, *triangleHeight, *fftFreqs;
  
    lowestFrequency   = 66.6666666;
    linearFilters     = 13;
    linearSpacing     = 66.66666666;
    logFilters        = 27;
    logSpacing        = 1.0711703;
  
    /* FFT and analysis window sizes */
    fftSize           = config.fftsize;
    fft               = new FFTReal(fftSize);

    totalFilters      = linearFilters + logFilters;
    logPower          = config.logpower;
  
    samplingRate      = config.FS;
  
    /* The number of cepstral componenents */
    nceps             = config.nceps;

    /* Set if user want C0 */
    WANT_C0           = (config.want_c0 ? 1 : 0);
  
    /* Allocate space for feature vector */
    if (WANT_C0 == 1) {
        ceps              = (double*)calloc(nceps+1, sizeof(double));
    } else {
        ceps              = (double*)calloc(nceps, sizeof(double));
    }
 
    /* Allocate space for local vectors */
    mfccDCTMatrix     = (double**)calloc(nceps+1, sizeof(double*));
    for (i = 0; i < nceps+1; i++) {
        mfccDCTMatrix[i]= (double*)calloc(totalFilters, sizeof(double)); 
    }

    mfccFilterWeights = (double**)calloc(totalFilters, sizeof(double*));
    for (i = 0; i < totalFilters; i++) {
        mfccFilterWeights[i] = (double*)calloc(fftSize, sizeof(double)); 
    }
    
    freqs  = (double*)calloc(totalFilters+2,sizeof(double));
    
    lower  = (double*)calloc(totalFilters,sizeof(double));
    center = (double*)calloc(totalFilters,sizeof(double));
    upper  = (double*)calloc(totalFilters,sizeof(double));
    
    triangleHeight = (double*)calloc(totalFilters,sizeof(double));
    fftFreqs       = (double*)calloc(fftSize,sizeof(double));
  
    for (i = 0; i < linearFilters; i++) {
        freqs[i] = lowestFrequency + ((double)i) * linearSpacing;
    }
  
    for (i = linearFilters; i < totalFilters+2; i++) {
        freqs[i] = freqs[linearFilters-1] * 
            pow(logSpacing, (double)(i-linearFilters+1));
    }
  
    /* Define lower, center and upper */
    memcpy(lower,  freqs,totalFilters*sizeof(double));
    memcpy(center, &freqs[1],totalFilters*sizeof(double));
    memcpy(upper,  &freqs[2],totalFilters*sizeof(double));
    
    for (i=0;i<totalFilters;i++){
        triangleHeight[i] = 2./(upper[i]-lower[i]);
    }
  
    for (i=0;i<fftSize;i++){
        fftFreqs[i] = ((double) i / ((double) fftSize ) * 
                       (double) samplingRate);
    }

    /* Build now the mccFilterWeight matrix */
    for (i=0;i<totalFilters;i++){

        for (j=0;j<fftSize;j++) {
      
            if ((fftFreqs[j] > lower[i]) && (fftFreqs[j] <= center[i])) {
          
                mfccFilterWeights[i][j] = triangleHeight[i] * 
                    (fftFreqs[j]-lower[i]) / (center[i]-lower[i]); 
          
            }
            else
            {
                mfccFilterWeights[i][j] = 0.0;
            }

            if ((fftFreqs[j]>center[i]) && (fftFreqs[j]<upper[i])) {

                mfccFilterWeights[i][j] = mfccFilterWeights[i][j]
                    + triangleHeight[i] * (upper[i]-fftFreqs[j]) 
                    / (upper[i]-center[i]);
            }
            else
            {
                mfccFilterWeights[i][j] = mfccFilterWeights[i][j] + 0.0;
            }
        }

    }

    /*
     * We calculate now mfccDCT matrix 
     * NB: +1 because of the DC component
     */

    const double pi = 3.14159265358979323846264338327950288;
  
    for (i = 0; i < nceps+1; i++) {
        for (j = 0; j < totalFilters; j++) {
            mfccDCTMatrix[i][j] = (1./sqrt((double) totalFilters / 2.))  
                * cos((double) i * ((double) j + 0.5) / (double) totalFilters * pi);
        }
    }

    for (j = 0; j < totalFilters; j++){
        mfccDCTMatrix[0][j] = (sqrt(2.)/2.) * mfccDCTMatrix[0][j];
    }
   
    /* The analysis window */
    window      = new Window<double>(config.window, fftSize);

    /* Allocate memory for the FFT */
    realOut     = (double*)calloc(fftSize, sizeof(double));
    imagOut     = (double*)calloc(fftSize, sizeof(double));

    earMag      = (double*)calloc(totalFilters, sizeof(double));
    fftMag      = (double*)calloc(fftSize/2, sizeof(double));
  
    free(freqs);
    free(lower);
    free(center);
    free(upper);
    free(triangleHeight);
    free(fftFreqs);
}

MFCC::~MFCC()
{
    int i;
  
    /* Free the structure */
    for (i = 0; i < nceps+1; i++) {
        free(mfccDCTMatrix[i]);
    }
    free(mfccDCTMatrix);
    
    for (i = 0; i < totalFilters; i++) {
        free(mfccFilterWeights[i]);
    }
    free(mfccFilterWeights);
    
    /* Free the feature vector */
    free(ceps);
    
    /* The analysis window */
    delete window;

    free(earMag);
    free(fftMag);
    
    /* Free the FFT */
    free(realOut);
    free(imagOut);

    delete fft;
}


/*
 * 
 * Extract the MFCC on the input frame 
 * 
 */ 
int MFCC::process(const double *inframe, double *outceps)
{
    double *inputData = (double *)malloc(fftSize * sizeof(double));
    for (int i = 0; i < fftSize; ++i) inputData[i] = inframe[i];

    window->cut(inputData);
  
    /* Calculate the fft on the input frame */
    fft->process(0, inputData, realOut, imagOut);

    free(inputData);

    return process(realOut, imagOut, outceps);
}

int MFCC::process(const double *real, const double *imag, double *outceps)
{
    int i, j;

    for (i = 0; i < fftSize/2; ++i) {
        fftMag[i] = sqrt(real[i] * real[i] + imag[i] * imag[i]);
    }

    for (i = 0; i < totalFilters; ++i) {
        earMag[i] = 0.0;
    }

    /* Multiply by mfccFilterWeights */
    for (i = 0; i < totalFilters; i++) {
        double tmp = 0.0;
        for (j = 0; j < fftSize/2; j++) {
            tmp = tmp + (mfccFilterWeights[i][j] * fftMag[j]);
        }
        if (tmp > 0) earMag[i] = log10(tmp);
	else earMag[i] = 0.0;

        if (logPower != 1.0) {
            earMag[i] = pow(earMag[i], logPower);
        }
    }

    /*
     * 
     * Calculate now the cepstral coefficients 
     * with or without the DC component
     *
     */
  
    if (WANT_C0 == 1) {
     
        for (i = 0; i < nceps+1; i++) {
            double tmp = 0.;
            for (j = 0; j < totalFilters; j++){
                tmp = tmp + mfccDCTMatrix[i][j] * earMag[j];
            }
            outceps[i] = tmp;
        }
    }
    else 
    {  
        for (i = 1; i < nceps+1; i++) {
            double tmp = 0.;
            for (j = 0; j < totalFilters; j++){
                tmp = tmp + mfccDCTMatrix[i][j] * earMag[j];
            }
            outceps[i-1] = tmp;
        }
    }
    
    return nceps;
}