pitch_a.c

G.729加解码程序

    sum = L_mac(sum, x[i], y[i]);

  return sum;
}

/*--------------------------------------------------------------------------*
 *  Function  Pitch_fr3_fast()                                              *
 *  ~~~~~~~~~~~~~~~~~~~~~~~~~~                                              *
 * Fast version of the pitch close loop.                                    *
 *--------------------------------------------------------------------------*/

Word16 Pitch_fr3_fast(/* (o)     : pitch period.                          */
  Word16 exc[],       /* (i)     : excitation buffer                      */
  Word16 xn[],        /* (i)     : target vector                          */
  Word16 h[],         /* (i) Q12 : impulse response of filters.           */
  Word16 L_subfr,     /* (i)     : Length of subframe                     */
  Word16 t0_min,      /* (i)     : minimum value in the searched range.   */
  Word16 t0_max,      /* (i)     : maximum value in the searched range.   */
  Word16 i_subfr,     /* (i)     : indicator for first subframe.          */
  Word16 *pit_frac    /* (o)     : chosen fraction.                       */
)
{
  Word16 t, t0;
  Word16 Dn[L_SUBFR];
  Word16 exc_tmp[L_SUBFR];
  Word32 max, corr, L_temp;

 /*-----------------------------------------------------------------*
  * Compute correlation of target vector with impulse response.     *
  *-----------------------------------------------------------------*/

  Cor_h_X(h, xn, Dn);

 /*-----------------------------------------------------------------*
  * Find maximum integer delay.                                     *
  *-----------------------------------------------------------------*/

  max = MIN_32;
  t0 = t0_min; /* Only to remove warning from some compilers */

  for(t=t0_min; t<=t0_max; t++)
  {
    corr = Dot_Product(Dn, &exc[-t], L_subfr);
    L_temp = L_sub(corr, max);
    if(L_temp > 0) {max = corr; t0 = t;  }
  }

 /*-----------------------------------------------------------------*
  * Test fractions.                                                 *
  *-----------------------------------------------------------------*/

  /* Fraction 0 */

  Pred_lt_3(exc, t0, 0, L_subfr);
  max = Dot_Product(Dn, exc, L_subfr);
  *pit_frac = 0;

  /* If first subframe and lag > 84 do not search fractional pitch */

  if( (i_subfr == 0) && (sub(t0, 84) > 0) )
    return t0;

  Copy(exc, exc_tmp, L_subfr);

  /* Fraction -1/3 */

  Pred_lt_3(exc, t0, -1, L_subfr);
  corr = Dot_Product(Dn, exc, L_subfr);
  L_temp = L_sub(corr, max);
  if(L_temp > 0) {
     max = corr;
     *pit_frac = -1;
     Copy(exc, exc_tmp, L_subfr);
  }

  /* Fraction +1/3 */

  Pred_lt_3(exc, t0, 1, L_subfr);
  corr = Dot_Product(Dn, exc, L_subfr);
  L_temp = L_sub(corr, max);
  if(L_temp > 0) {
     max = corr;
     *pit_frac =  1;
  }
  else
    Copy(exc_tmp, exc, L_subfr);

  return t0;
}


/*---------------------------------------------------------------------*
 * Function  G_pitch:                                                  *
 *           ~~~~~~~~                                                  *
 *---------------------------------------------------------------------*
 * Compute correlations <xn,y1> and <y1,y1> to use in gains quantizer. *
 * Also compute the gain of pitch. Result in Q14                       *
 *  if (gain < 0)  gain =0                                             *
 *  if (gain >1.2) gain =1.2                                           *
 *---------------------------------------------------------------------*/


Word16 G_pitch(      /* (o) Q14 : Gain of pitch lag saturated to 1.2       */
  Word16 xn[],       /* (i)     : Pitch target.                            */
  Word16 y1[],       /* (i)     : Filtered adaptive codebook.              */
  Word16 g_coeff[],  /* (i)     : Correlations need for gain quantization. */
  Word16 L_subfr     /* (i)     : Length of subframe.                      */
)
{
   Word16 i;
   Word16 xy, yy, exp_xy, exp_yy, gain;
   Word32 s;

   Word16 scaled_y1[L_SUBFR];

   /* divide "y1[]" by 4 to avoid overflow */

   for(i=0; i<L_subfr; i++)
     scaled_y1[i] = shr(y1[i], 2);

   /* Compute scalar product <y1[],y1[]> */

   Overflow = 0;
   s = 1;                    /* Avoid case of all zeros */
   for(i=0; i<L_subfr; i++)
     s = L_mac(s, y1[i], y1[i]);

   if (Overflow == 0) {
     exp_yy = norm_l(s);
     yy     = round( L_shl(s, exp_yy) );
   }
   else {
     s = 1;                  /* Avoid case of all zeros */
     for(i=0; i<L_subfr; i++)
       s = L_mac(s, scaled_y1[i], scaled_y1[i]);
     exp_yy = norm_l(s);
     yy     = round( L_shl(s, exp_yy) );
     exp_yy = sub(exp_yy, 4);
   }

   /* Compute scalar product <xn[],y1[]> */

   Overflow = 0;
   s = 0;
   for(i=0; i<L_subfr; i++)
     s = L_mac(s, xn[i], y1[i]);

   if (Overflow == 0) {
     exp_xy = norm_l(s);
     xy     = round( L_shl(s, exp_xy) );
   }
   else {
     s = 0;
     for(i=0; i<L_subfr; i++)
       s = L_mac(s, xn[i], scaled_y1[i]);
     exp_xy = norm_l(s);
     xy     = round( L_shl(s, exp_xy) );
     exp_xy = sub(exp_xy, 2);
   }

   g_coeff[0] = yy;
   g_coeff[1] = sub(15, exp_yy);
   g_coeff[2] = xy;
   g_coeff[3] = sub(15, exp_xy);

   /* If (xy <= 0) gain = 0 */


   if (xy <= 0)
   {
      g_coeff[3] = -15;   /* Force exp_xy to -15 = (15-30) */
      return( (Word16) 0);
   }

   /* compute gain = xy/yy */

   xy = shr(xy, 1);             /* Be sure xy < yy */
   gain = div_s( xy, yy);

   i = sub(exp_xy, exp_yy);
   gain = shr(gain, i);         /* saturation if > 1.99 in Q14 */

   /* if(gain >1.2) gain = 1.2  in Q14 */

   if( sub(gain, 19661) > 0)
   {
     gain = 19661;
   }


   return(gain);
}



/*----------------------------------------------------------------------*
 *    Function Enc_lag3                                                 *
 *             ~~~~~~~~                                                 *
 *   Encoding of fractional pitch lag with 1/3 resolution.              *
 *----------------------------------------------------------------------*
 * The pitch range for the first subframe is divided as follows:        *
 *   19 1/3  to   84 2/3   resolution 1/3                               *
 *   85      to   143      resolution 1                                 *
 *                                                                      *
 * The period in the first subframe is encoded with 8 bits.             *
 * For the range with fractions:                                        *
 *   index = (T-19)*3 + frac - 1;   where T=[19..85] and frac=[-1,0,1]  *
 * and for the integer only range                                       *
 *   index = (T - 85) + 197;        where T=[86..143]                   *
 *----------------------------------------------------------------------*
 * For the second subframe a resolution of 1/3 is always used, and the  *
 * search range is relative to the lag in the first subframe.           *
 * If t0 is the lag in the first subframe then                          *
 *  t_min=t0-5   and  t_max=t0+4   and  the range is given by           *
 *       t_min - 2/3   to  t_max + 2/3                                  *
 *                                                                      *
 * The period in the 2nd subframe is encoded with 5 bits:               *
 *   index = (T-(t_min-1))*3 + frac - 1;    where T[t_min-1 .. t_max+1] *
 *----------------------------------------------------------------------*/


Word16 Enc_lag3(     /* output: Return index of encoding */
  Word16 T0,         /* input : Pitch delay              */
  Word16 T0_frac,    /* input : Fractional pitch delay   */
  Word16 *T0_min,    /* in/out: Minimum search delay     */
  Word16 *T0_max,    /* in/out: Maximum search delay     */
  Word16 pit_min,    /* input : Minimum pitch delay      */
  Word16 pit_max,    /* input : Maximum pitch delay      */
  Word16 pit_flag    /* input : Flag for 1st subframe    */
)
{
  Word16 index, i;

  if (pit_flag == 0)   /* if 1st subframe */
  {
    /* encode pitch delay (with fraction) */

    if (sub(T0, 85) <= 0)
    {
      /* index = t0*3 - 58 + t0_frac   */
      i = add(add(T0, T0), T0);
      index = add(sub(i, 58), T0_frac);
    }
    else {
      index = add(T0, 112);
    }

    /* find T0_min and T0_max for second subframe */

    *T0_min = sub(T0, 5);
    if (sub(*T0_min, pit_min) < 0)
    {
      *T0_min = pit_min;
    }

    *T0_max = add(*T0_min, 9);
    if (sub(*T0_max, pit_max) > 0)
    {
      *T0_max = pit_max;
      *T0_min = sub(*T0_max, 9);
    }
  }
  else      /* if second subframe */
  {

    /* i = t0 - t0_min;               */
    /* index = i*3 + 2 + t0_frac;     */
    i = sub(T0, *T0_min);
    i = add(add(i, i), i);
    index = add(add(i, 2), T0_frac);
  }


  return index;
}