mfcc-core.c

julius version 4.12.about sound recognition.

  for(i = framesize; i >= 2; i--)
    wave[i] -= wave[i - 1] * preEmph;
  wave[1] *= 1.0 - preEmph;  
}

/** 
 * Apply hamming window.
 * 
 * @param wave [i/o] waveform data in the current frame
 * @param framesize [in] frame size
 * @param w [i/o] MFCC calculation work area
 */
void Hamming(float *wave, int framesize, MFCCWork *w)
{
  int i;
#ifdef MFCC_SINCOS_TABLE
  for(i = 1; i <= framesize; i++)
    wave[i] *= w->costbl_hamming[i-1];
#else
  float a;
  a = 2 * PI / (framesize - 1);
  for(i = 1; i <= framesize; i++)
    wave[i] *= 0.54 - 0.46 * cos(a * (i - 1));
#endif
}

/** 
 * Apply FFT
 * 
 * @param xRe [i/o] real part of waveform
 * @param xIm [i/o] imaginal part of waveform
 * @param p [in] 2^p = FFT point
 * @param w [i/o] MFCC calculation work area
 */
void FFT(float *xRe, float *xIm, int p, MFCCWork *w)
{
  int i, ip, j, k, m, me, me1, n, nv2;
  double uRe, uIm, vRe, vIm, wRe, wIm, tRe, tIm;
  
  n = 1<<p;
  nv2 = n / 2;
  
  j = 0;
  for(i = 0; i < n-1; i++){
    if(j > i){
      tRe = xRe[j];      tIm = xIm[j];
      xRe[j] = xRe[i];   xIm[j] = xIm[i];
      xRe[i] = tRe;      xIm[i] = tIm;
    }
    k = nv2;
    while(j >= k){
      j -= k;      k /= 2;
    }
    j += k;
  }

  for(m = 1; m <= p; m++){
    me = 1<<m;                me1 = me / 2;
    uRe = 1.0;                uIm = 0.0;
#ifdef MFCC_SINCOS_TABLE
    wRe = w->costbl_fft[m-1];    wIm = w->sintbl_fft[m-1];
#else
    wRe = cos(PI / me1);      wIm = -sin(PI / me1);
#endif
    for(j = 0; j < me1; j++){
      for(i = j; i < n; i += me){
	ip = i + me1;
	tRe = xRe[ip] * uRe - xIm[ip] * uIm;
	tIm = xRe[ip] * uIm + xIm[ip] * uRe;
	xRe[ip] = xRe[i] - tRe;   xIm[ip] = xIm[i] - tIm;
	xRe[i] += tRe;            xIm[i] += tIm;
      }
      vRe = uRe * wRe - uIm * wIm;   vIm = uRe * wIm + uIm * wRe;
      uRe = vRe;                     uIm = vIm;
    }
  }
}


/** 
 * Convert wave -> (spectral subtraction) -> mel-frequency filterbank
 * 
 * @param wave [in] waveform data in the current frame
 * @param w [i/o] MFCC calculation work area
 * @param para [in] configuration parameters
 */
void
MakeFBank(float *wave, MFCCWork *w, Value *para)
{
  int k, bin, i;
  double Re, Im, A, P, NP, H, temp;

  for(k = 1; k <= para->framesize; k++){
    w->fb.Re[k - 1] = wave[k];  w->fb.Im[k - 1] = 0.0;  /* copy to workspace */
  }
  for(k = para->framesize + 1; k <= w->fb.fftN; k++){
    w->fb.Re[k - 1] = 0.0;      w->fb.Im[k - 1] = 0.0;  /* pad with zeroes */
  }
  
  /* Take FFT */
  FFT(w->fb.Re, w->fb.Im, w->fb.n, w);

  if (w->ssbuf != NULL) {
    /* Spectral Subtraction */
    for(k = 1; k <= w->fb.fftN; k++){
      Re = w->fb.Re[k - 1];  Im = w->fb.Im[k - 1];
      P = sqrt(Re * Re + Im * Im);
      NP = w->ssbuf[k - 1];
      if((P * P -  w->ss_alpha * NP * NP) < 0){
	H = w->ss_floor;
      }else{
	H = sqrt(P * P - w->ss_alpha * NP * NP) / P;
      }
      w->fb.Re[k - 1] = H * Re;
      w->fb.Im[k - 1] = H * Im;
    }
  }

  /* Fill filterbank channels */ 
  for(i = 1; i <= para->fbank_num; i++)
    w->fbank[i] = 0.0;
  
  if (para->usepower) {
    for(k = w->fb.klo; k <= w->fb.khi; k++){
      Re = w->fb.Re[k-1]; Im = w->fb.Im[k-1];
      A = Re * Re + Im * Im;
      bin = w->fb.loChan[k];
      Re = w->fb.loWt[k] * A;
      if(bin > 0) w->fbank[bin] += Re;
      if(bin < para->fbank_num) w->fbank[bin + 1] += A - Re;
    }
  } else {
    for(k = w->fb.klo; k <= w->fb.khi; k++){
      Re = w->fb.Re[k-1]; Im = w->fb.Im[k-1];
      A = sqrt(Re * Re + Im * Im);
      bin = w->fb.loChan[k];
      Re = w->fb.loWt[k] * A;
      if(bin > 0) w->fbank[bin] += Re;
      if(bin < para->fbank_num) w->fbank[bin + 1] += A - Re;
    }
  }

  /* Take logs */
  for(bin = 1; bin <= para->fbank_num; bin++){ 
    temp = w->fbank[bin];
    if(temp < 1.0) temp = 1.0;
    w->fbank[bin] = log(temp);  
  }
}

/** 
 * Calculate 0'th cepstral coefficient.
 * 
 * @param w [i/o] MFCC calculation work area
 * @param para [in] configuration parameters
 * 
 * @return 
 */
float CalcC0(MFCCWork *w, Value *para)
{
  int i; 
  float S;
  
  S = 0.0;
  for(i = 1; i <= para->fbank_num; i++)
    S += w->fbank[i];
  return S * w->sqrt2var;
}

/** 
 * Apply DCT to filterbank to make MFCC.
 * 
 * @param mfcc [out] output MFCC vector
 * @param para [in] configuration parameters
 * @param w [i/o] MFCC calculation work area
 */
void MakeMFCC(float *mfcc, Value *para, MFCCWork *w)
{
#ifdef MFCC_SINCOS_TABLE
  int i, j, k;
  k = 0;
  /* Take DCT */
  for(i = 0; i < para->mfcc_dim; i++){
    mfcc[i] = 0.0;
    for(j = 1; j <= para->fbank_num; j++)
      mfcc[i] += w->fbank[j] * w->costbl_makemfcc[k++];
    mfcc[i] *= w->sqrt2var;
  }
#else
  int i, j;
  float B, C;
  
  B = PI / para->fbank_num;
  /* Take DCT */
  for(i = 1; i <= para->mfcc_dim; i++){
    mfcc[i - 1] = 0.0;
    C = i * B;
    for(j = 1; j <= para->fbank_num; j++)
      mfcc[i - 1] += w->fbank[j] * cos(C * (j - 0.5));
    mfcc[i - 1] *= w->sqrt2var;     
  }
#endif
}

/** 
 * Re-scale cepstral coefficients.
 * 
 * @param mfcc [i/o] a MFCC vector
 * @param para [in] configuration parameters
 * @param w [i/o] MFCC calculation work area
 */
void WeightCepstrum (float *mfcc, Value *para, MFCCWork *w)
{
#ifdef MFCC_SINCOS_TABLE
  int i;
  for(i=0;i<para->mfcc_dim;i++) {
    mfcc[i] *= w->sintbl_wcep[i];
  }
#else
  int i;
  float a, b, *cepWin;
  
  cepWin = (float *)mymalloc(para->mfcc_dim * sizeof(float));
  a = PI / para->lifter;
  b = para->lifter / 2.0;
  
  for(i = 0; i < para->mfcc_dim; i++){
    cepWin[i] = 1.0 + b * sin((i + 1) * a);
    mfcc[i] *= cepWin[i];
  }
  
  free(cepWin);
#endif
}

/************************************************************************/
/************************************************************************/
/************************************************************************/
/************************************************************************/
/************************************************************************/
/** 
 * Setup work area for parameters, values, buffers, tables to compute
 * MFCC vectors, with a given parameter configurations
 * 
 * @param para [in] configuration parameters
 *
 * @return pointer to the newly allocated work area.
 */
MFCCWork *
WMP_work_new(Value *para)
{
  MFCCWork *w;

  /* newly allocated area should be cleared */
  w = (MFCCWork *)mymalloc(sizeof(MFCCWork));
  memset(w, 0, sizeof(MFCCWork));

  /* set filterbank information */
  if (InitFBank(w, para) == FALSE) return NULL;

#ifdef MFCC_SINCOS_TABLE
  /* prepare tables */
  make_costbl_hamming(w, para->framesize);
  make_fft_table(w, w->fb.n);
  if (para->mfcc_dim >= 0) {
    make_costbl_makemfcc(w, para->fbank_num, para->mfcc_dim);
    make_sintbl_wcep(w, para->lifter, para->mfcc_dim);
  }
#endif

  /* prepare some buffers */
  w->fbank = (double *)mymalloc((para->fbank_num+1)*sizeof(double));
  w->bf = (float *)mymalloc(w->fb.fftN * sizeof(float));
  w->bflen = w->fb.fftN;

  return w;
}

/** 
 * Calculate MFCC and log energy for one frame.  Perform spectral subtraction
 * if @a ssbuf is specified.
 * 
 * @param w [i/o] MFCC calculation work area
 * @param mfcc [out] buffer to hold the resulting MFCC vector
 * @param para [in] configuration parameters
 */
void
WMP_calc(MFCCWork *w, float *mfcc, Value *para)
{
  float energy = 0.0;
  float c0 = 0.0;
  int p;

  if (para->zmeanframe) {
    ZMeanFrame(w->bf, para->framesize);
  }

  if (para->energy && para->raw_e) {
    /* calculate log raw energy */
    energy = CalcLogRawE(w->bf, para->framesize);
  }
  /* pre-emphasize */
  PreEmphasise(w->bf, para->framesize, para->preEmph);
  /* hamming window */
  Hamming(w->bf, para->framesize, w);
  if (para->energy && ! para->raw_e) {
    /* calculate log energy */
    energy = CalcLogRawE(w->bf, para->framesize);
  }
  /* filterbank */
  MakeFBank(w->bf, w, para);
  /* 0'th cepstral parameter */
  if (para->c0) c0 = CalcC0(w, para);
  /* MFCC */
  MakeMFCC(mfcc, para, w);
  /* weight cepstrum */
  WeightCepstrum(mfcc, para, w);
  /* set energy to mfcc */
  p = para->mfcc_dim;
  if (para->c0) mfcc[p++] = c0;
  if (para->energy) mfcc[p++] = energy;
}

/** 
 * Free all work area for MFCC computation
 * 
 * @param w [i/o] MFCC calculation work area
 */
void
WMP_free(MFCCWork *w)
{
  if (w->fbank) {
    FreeFBank(&(w->fb));
    free(w->fbank);
    free(w->bf);
    w->fbank = NULL;
    w->bf = NULL;
  }
#ifdef MFCC_SINCOS_TABLE
  if (w->costbl_hamming) {
    free(w->costbl_hamming);
    w->costbl_hamming = NULL;
  }
  if (w->costbl_fft) {
    free(w->costbl_fft);
    w->costbl_fft = NULL;
  }
  if (w->sintbl_fft) {
    free(w->sintbl_fft);
    w->sintbl_fft = NULL;
  }
  if (w->costbl_makemfcc) {
    free(w->costbl_makemfcc);
    w->costbl_makemfcc = NULL;
  }
  if (w->sintbl_wcep) {
    free(w->sintbl_wcep);
    w->sintbl_wcep = NULL;
  }
#endif
  free(w);
}