cod_ld8a.c

本程序的压缩编码是G.729的编解码程序

    /*--------------------------------------------------------------------*
     * Find interpolated LPC parameters in all subframes                  *
     * The interpolated parameters are in array Aq_t[].                   *
     *--------------------------------------------------------------------*/

    Int_qlpc(lsp_old_q, lsp_new_q, Aq_t);

    /* Compute A(z/gamma) */

    Weight_Az(&Aq_t[0],   GAMMA1, M, &Ap_t[0]);
    Weight_Az(&Aq_t[MP1], GAMMA1, M, &Ap_t[MP1]);

    /* update the LSPs for the next frame */

    Copy(lsp_new,   lsp_old,   M);
    Copy(lsp_new_q, lsp_old_q, M);
  }

 /*----------------------------------------------------------------------*
  * - Find the weighted input speech w_sp[] for the whole speech frame   *
  * - Find the open-loop pitch delay                                     *
  *----------------------------------------------------------------------*/

  Residu(&Aq_t[0], &speech[0], &exc[0], L_SUBFR);
  Residu(&Aq_t[MP1], &speech[L_SUBFR], &exc[L_SUBFR], L_SUBFR);

  {
    Word16 Ap1[MP1];

    Ap = Ap_t;
    Ap1[0] = 4096;
    for(i=1; i<=M; i++)    /* Ap1[i] = Ap[i] - 0.7 * Ap[i-1]; */
       Ap1[i] = sub(Ap[i], mult(Ap[i-1], 22938));
    Syn_filt(Ap1, &exc[0], &wsp[0], L_SUBFR, mem_w, 1);

    Ap += MP1;
    for(i=1; i<=M; i++)    /* Ap1[i] = Ap[i] - 0.7 * Ap[i-1]; */
       Ap1[i] = sub(Ap[i], mult(Ap[i-1], 22938));
    Syn_filt(Ap1, &exc[L_SUBFR], &wsp[L_SUBFR], L_SUBFR, mem_w, 1);
  }

  /* Find open loop pitch lag */

  T_op = Pitch_ol_fast(wsp, PIT_MAX, L_FRAME);

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

  T0_min = sub(T_op, 3);
  if (sub(T0_min,PIT_MIN)<0) {
    T0_min = PIT_MIN;
  }

  T0_max = add(T0_min, 6);
  if (sub(T0_max ,PIT_MAX)>0)
  {
     T0_max = PIT_MAX;
     T0_min = sub(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 2 times.                             *
  *     - find the weighted LPC coefficients                               *
  *     - find the LPC residual signal res[]                               *
  *     - 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                                           *
  *     - find target vector for codebook search                           *
  *     - codebook search                                                  *
  *     - VQ of pitch and codebook gains                                   *
  *     - update states of weighting filter                                *
  *------------------------------------------------------------------------*/

  Aq = Aq_t;    /* pointer to interpolated quantized LPC parameters */
  Ap = Ap_t;    /* pointer to weighted LPC coefficients             */

  for (i_subfr = 0;  i_subfr < L_FRAME; i_subfr += L_SUBFR)
  {

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

    h1[0] = 4096;
    Set_zero(&h1[1], L_SUBFR-1);
    Syn_filt(Ap, h1, h1, L_SUBFR, &h1[1], 0);

   /*----------------------------------------------------------------------*
    *  Find the target vector for pitch search:                            *
    *----------------------------------------------------------------------*/

    Syn_filt(Ap, &exc[i_subfr], xn, L_SUBFR, mem_w0, 0);

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

    T0 = Pitch_fr3_fast(&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 filtered pitch exc                                     *
    *   - compute pitch gain and limit between 0 and 1.2              *
    *   - update target vector for codebook search                    *
    *-----------------------------------------------------------------*/

    Syn_filt(Ap, &exc[i_subfr], y1, L_SUBFR, mem_zero, 0);

    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 (sub(gain_pit, GPCLIP) > 0) {
        gain_pit = GPCLIP;
      }
    }

    /* xn2[i]   = xn[i] - y1[i] * gain_pit  */

    for (i = 0; i < L_SUBFR; i++)
    {
      L_temp = L_mult(y1[i], gain_pit);
      L_temp = L_shl(L_temp, 1);               /* gain_pit in Q14 */
      xn2[i] = sub(xn[i], extract_h(L_temp));
    }


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

    index = ACELP_Code_A(xn2, h1, T0, sharp, code, y2, &i);

    *ana++ = index;        /* Positions index */
    *ana++ = i;            /* Signs index     */


   /*-----------------------------------------------------*
    * - Quantization of gains.                            *
    *-----------------------------------------------------*/

    g_coeff_cs[0]     = g_coeff[0];            /* <y1,y1> */
    exp_g_coeff_cs[0] = negate(g_coeff[1]);    /* Q-Format:XXX -> JPN */
    g_coeff_cs[1]     = negate(g_coeff[2]);    /* (xn,y1) -> -2<xn,y1> */
    exp_g_coeff_cs[1] = negate(add(g_coeff[3], 1)); /* Q-Format:XXX -> JPN */

    Corr_xy2( xn, y1, y2, g_coeff_cs, exp_g_coeff_cs );  /* Q0 Q0 Q12 ^Qx ^Q0 */
                         /* g_coeff_cs[3]:exp_g_coeff_cs[3] = <y2,y2>   */
                         /* g_coeff_cs[4]:exp_g_coeff_cs[4] = -2<xn,y2> */
                         /* g_coeff_cs[5]:exp_g_coeff_cs[5] = 2<y1,y2>  */

    *ana++ = Qua_gain(code, g_coeff_cs, exp_g_coeff_cs,
                         L_SUBFR, &gain_pit, &gain_code, taming);


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

    sharp = gain_pit;
    if (sub(sharp, SHARPMAX) > 0) { sharp = SHARPMAX;         }
    if (sub(sharp, SHARPMIN) < 0) { sharp = SHARPMIN;         }

   /*------------------------------------------------------*
    * - Find the total excitation                          *
    * - update filters memories for finding the target     *
    *   vector in the next subframe                        *
    *------------------------------------------------------*/

    for (i = 0; i < L_SUBFR;  i++)
    {
      /* exc[i] = gain_pit*exc[i] + gain_code*code[i]; */
      /* exc[i]  in Q0   gain_pit in Q14               */
      /* code[i] in Q13  gain_cod in Q1                */

      L_temp = L_mult(exc[i+i_subfr], gain_pit);
      L_temp = L_mac(L_temp, code[i], gain_code);
      L_temp = L_shl(L_temp, 1);
      exc[i+i_subfr] = round(L_temp);
    }

    update_exc_err(gain_pit, T0);

    for (i = L_SUBFR-M, j = 0; i < L_SUBFR; i++, j++)
    {
      temp       = extract_h(L_shl( L_mult(y1[i], gain_pit),  1) );
      k          = extract_h(L_shl( L_mult(y2[i], gain_code), 2) );
      mem_w0[j]  = sub(xn[i], add(temp, k));
    }

    Aq += MP1;           /* interpolated LPC parameters for next subframe */
    Ap += 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;
}