cod_ld8k.c

具有浮点指令的g.729语音压缩编码

  }

 /*----------------------------------------------------------------------*
  * - Find the weighting factors                                         *
  *----------------------------------------------------------------------*/

  perc_var(gamma1, gamma2, lsf_int, lsf_new, rc);


 /*----------------------------------------------------------------------*
  * - Find the weighted input speech w_sp[] for the whole speech frame   *
  * - Find the open-loop pitch delay for the whole speech frame          *
  * - Set the range for searching closed-loop pitch in 1st subframe      *
  *----------------------------------------------------------------------*/

  weight_az(&A_t[0], gamma1[0], M, Ap1);
  weight_az(&A_t[0], gamma2[0], M, Ap2);
  residu(Ap1, &speech[0], &wsp[0], L_SUBFR);
  syn_filt(Ap2, &wsp[0], &wsp[0], L_SUBFR, mem_w, 1);

  weight_az(&A_t[MP1], gamma1[1], M, Ap1);
  weight_az(&A_t[MP1], gamma2[1], M, Ap2);
  residu(Ap1, &speech[L_SUBFR], &wsp[L_SUBFR], L_SUBFR);
  syn_filt(Ap2, &wsp[L_SUBFR], &wsp[L_SUBFR], L_SUBFR, mem_w, 1);

  /* Find open loop pitch lag for whole speech frame */

  T_op = pitch_ol(wsp, PIT_MIN, PIT_MAX, L_FRAME);

  /* range for closed loop pitch search in 1st subframe */

  t0_min = T_op - 3;
  if (t0_min < PIT_MIN) t0_min = PIT_MIN;
  t0_max = t0_min + 6;
  if (t0_max > PIT_MAX)
    {
       t0_max = PIT_MAX;
       t0_min = t0_max - 6;
    }

 /*------------------------------------------------------------------------*
  *          Loop for every subframe in the analysis frame                 *
  *------------------------------------------------------------------------*
  *  To find the pitch and innovation parameters. The subframe size is     *
  *  L_SUBFR and the loop is repeated L_FRAME/L_SUBFR times.               *
  *     - find the weighted LPC coefficients                               *
  *     - find the LPC residual signal                                     *
  *     - compute the target signal for pitch search                       *
  *     - compute impulse response of weighted synthesis filter (h1[])     *
  *     - find the closed-loop pitch parameters                            *
  *     - encode the pitch delay                                           *
  *     - update the impulse response h1[] by including fixed-gain pitch   *
  *     - find target vector for codebook search                           *
  *     - codebook search                                                  *
  *     - encode codebook address                                          *
  *     - VQ of pitch and codebook gains                                   *
  *     - find synthesis speech                                            *
  *     - update states of weighting filter                                *
  *------------------------------------------------------------------------*/

  A  = A_t;     /* pointer to interpolated LPC parameters           */
  Aq = Aq_t;    /* pointer to interpolated quantized LPC parameters */

  i_gamma = 0;

  for (i_subfr = 0;  i_subfr < L_FRAME; i_subfr += L_SUBFR)
  {
   /*---------------------------------------------------------------*
    * Find the weighted LPC coefficients for the weighting filter.  *
    *---------------------------------------------------------------*/

    weight_az(A, gamma1[i_gamma], M, Ap1);
    weight_az(A, gamma2[i_gamma], M, Ap2);
    i_gamma++;

   /*---------------------------------------------------------------*
    * Compute impulse response, h1[], of weighted synthesis filter  *
    *---------------------------------------------------------------*/

    for (i = 0; i <= M; i++) ai_zero[i] = Ap1[i];
    syn_filt(Aq, ai_zero, h1, L_SUBFR, zero, 0);
    syn_filt(Ap2, h1, h1, L_SUBFR, zero, 0);

   /*------------------------------------------------------------------------*
    *                                                                        *
    *          Find the target vector for pitch search:                      *
    *          ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~                       *
    *                                                                        *
    *              |------|  res[n]                                          *
    *  speech[n]---| A(z) |--------                                          *
    *              |------|       |   |--------| error[n]  |------|          *
    *                    zero -- (-)--| 1/A(z) |-----------| W(z) |-- target *
    *                    exc          |--------|           |------|          *
    *                                                                        *
    * Instead of subtracting the zero-input response of filters from         *
    * the weighted input speech, the above configuration is used to          *
    * compute the target vector. This configuration gives better performance *
    * with fixed-point implementation. The memory of 1/A(z) is updated by    *
    * filtering (res[n]-exc[n]) through 1/A(z), or simply by subtracting     *
    * the synthesis speech from the input speech:                            *
    *    error[n] = speech[n] - syn[n].                                      *
    * The memory of W(z) is updated by filtering error[n] through W(z),      *
    * or more simply by subtracting the filtered adaptive and fixed          *
    * codebook excitations from the target:                                  *
    *     target[n] - gain_pit*y1[n] - gain_code*y2[n]                       *
    * as these signals are already available.                                *
    *                                                                        *
    *------------------------------------------------------------------------*/


    residu(Aq, &speech[i_subfr], &exc[i_subfr], L_SUBFR);   /* LPC residual */

    syn_filt(Aq, &exc[i_subfr], error, L_SUBFR, mem_err, 0);

    residu(Ap1, error, xn, L_SUBFR);

    syn_filt(Ap2, xn, xn, L_SUBFR, mem_w0, 0);    /* target signal xn[]*/

   /*----------------------------------------------------------------------*
    *                 Closed-loop fractional pitch search                  *
    *----------------------------------------------------------------------*/

    t0 = pitch_fr3(&exc[i_subfr], xn, h1, L_SUBFR, t0_min, t0_max,
                              i_subfr, &t0_frac);


    index = enc_lag3(t0, t0_frac, &t0_min, &t0_max,PIT_MIN,PIT_MAX,i_subfr);

    *ana++ = index;
    if (i_subfr == 0)
      *ana++ = parity_pitch(index);


   /*-----------------------------------------------------------------*
    *   - find unity gain pitch excitation (adaptive codebook entry)  *
    *     with fractional interpolation.                              *
    *   - find filtered pitch exc. y1[]=exc[] convolve with h1[])     *
    *   - compute pitch gain and limit between 0 and 1.2              *
    *   - update target vector for codebook search                    *
    *   - find LTP residual.                                          *
    *-----------------------------------------------------------------*/

    pred_lt_3(&exc[i_subfr], t0, t0_frac, L_SUBFR);

    convolve(&exc[i_subfr], h1, y1, L_SUBFR);

    gain_pit = g_pitch(xn, y1, g_coeff, L_SUBFR);

    /* clip pitch gain if taming is necessary */
    taming = test_err(t0, t0_frac);

    if( taming == 1){
      if ( gain_pit>  GPCLIP) {
        gain_pit = GPCLIP;
      }
    }

    for (i = 0; i < L_SUBFR; i++)
       xn2[i] = xn[i] - y1[i]*gain_pit;

   /*-----------------------------------------------------*
    * - Innovative codebook search.                       *
    *-----------------------------------------------------*/

    index = ACELP_codebook(xn2, h1, t0, sharp, i_subfr, code, y2, &i);
    *ana++ = index;        /* Positions index */
    *ana++ = i;            /* Signs index     */


   /*-----------------------------------------------------*
    * - Quantization of gains.                            *
    *-----------------------------------------------------*/
    corr_xy2(xn, y1, y2, g_coeff);

    *ana++ =qua_gain(code, g_coeff, L_SUBFR, &gain_pit, &gain_code, taming );

   /*------------------------------------------------------------*
    * - Update pitch sharpening "sharp" with quantized gain_pit  *
    *------------------------------------------------------------*/

    sharp = gain_pit;
    if (sharp > SHARPMAX) sharp = SHARPMAX;
    if (sharp < SHARPMIN) sharp = SHARPMIN;
    /*------------------------------------------------------*
     * - Find the total excitation                          *
     * - find synthesis speech corresponding to exc[]       *
     * - update filters' memories for finding the target    *
     *   vector in the next subframe                        *
     *   (update error[-m..-1] and mem_w0[])                *
     *   update error function for taming process           *
     *------------------------------------------------------*/

    for (i = 0; i < L_SUBFR;  i++)
      exc[i+i_subfr] = gain_pit*exc[i+i_subfr] + gain_code*code[i];

    update_exc_err(gain_pit, t0);

    syn_filt(Aq, &exc[i_subfr], &synth[i_subfr], L_SUBFR, mem_syn, 1);

    for (i = L_SUBFR-M, j = 0; i < L_SUBFR; i++, j++)
      {
         mem_err[j] = speech[i_subfr+i] - synth[i_subfr+i];
         mem_w0[j]  = xn[i] - gain_pit*y1[i] - gain_code*y2[i];
      }
    A  += MP1;      /* interpolated LPC parameters for next subframe */
    Aq += MP1;

  }

  /*--------------------------------------------------*
   * Update signal for next frame.                    *
   * -> shift to the left by L_FRAME:                 *
   *     speech[], wsp[] and  exc[]                   *
   *--------------------------------------------------*/

  copy(&old_speech[L_FRAME], &old_speech[0], L_TOTAL-L_FRAME);
  copy(&old_wsp[L_FRAME], &old_wsp[0], PIT_MAX);
  copy(&old_exc[L_FRAME], &old_exc[0], PIT_MAX+L_INTERPOL);


  return;
}