C++ L_shl函数代码示例

static void Calc_RCoeff(Word16 *Coeff, Word16 *RCoeff, Word16 *sh_RCoeff)
{
  Word16 i, j;
  Word16 sh1;
  Word32 L_acc;
  
  /* RCoeff[0] = SUM(j=0->M) Coeff[j] ** 2 */
  L_acc = 0L;
  for(j=0; j <= M; j++) {
    L_acc = L_mac(L_acc, Coeff[j], Coeff[j]);
  }
  
  /* Compute exponent RCoeff */
  sh1 = norm_l(L_acc);
  L_acc = L_shl(L_acc, sh1);
  RCoeff[0] = round(L_acc);
  
  /* RCoeff[i] = SUM(j=0->M-i) Coeff[j] * Coeff[j+i] */
  for(i=1; i<=M; i++) {
    L_acc = 0L;
    for(j=0; j<=M-i; j++) {
      L_acc = L_mac(L_acc, Coeff[j], Coeff[j+i]);
    }
    L_acc = L_shl(L_acc, sh1);
    RCoeff[i] = round(L_acc);
  }
  *sh_RCoeff = sh1;
  return;
}

void Deemph_32_(
     Word16 x_hi[],      /* (i)     : input signal (bit31..16) */
     Word16 x_lo[],      /* (i)     : input signal (bit15..4)  */
     Word16 y[],         /* (o)     : output signal (x16)      */
     Word16 mu,          /* (i) Q15 : deemphasis factor        */
     Word16 L,           /* (i)     : vector size              */
     Word16 * mem        /* (i/o)   : memory (y[-1])           */
)
{
    Word16 i;
    Word32 L_tmp;

    /* L_tmp = hi<<16 + lo<<4 */

    L_tmp = (Word32)x_hi[0] << 16;
    L_tmp = L_tmp + ((Word32)x_lo[0] << 4);
    L_tmp = L_shl(L_tmp, 4);
    L_tmp = L_mac(L_tmp, *mem, mu);          /* saturation can occur here */
    y[0] = round16(L_tmp);

    for (i = 1; i < L; i++)
    {
        L_tmp = (Word32)x_hi[i] << 16;
        L_tmp = L_tmp + ((Word32)x_lo[i] << 4);
        L_tmp = L_shl(L_tmp, 4);
        L_tmp = L_mac(L_tmp, y[i - 1], mu);     /* saturation can occur here */
        y[i] = round16(L_tmp);
    }

    *mem = y[L - 1];

    return;
}

void get_pq_polynomials(
    Word32 *f,     /* Q23 */
    Word16 *lsp)   /* Q15 */
{
    Word16 i, n, hi, lo;
    Word16 index, offset, coslsp, c;
    Word32 a0;

    f[0] = L_mult(2048, 2048);                                        // 1.0 Q23
    for(i = 1; i <= LPCO ; i++)
        f[i]= 0;

    for(n=1; n<=(LPCO>>1); n++) {

        /* cosine mapping */
        index = shr(lsp[2*n-2],9);                                     // Q6
        offset = lsp[2*n-2]&(Word16)0x01ff;                            // Q9
        a0 = L_mult(sub(costable[index+1], costable[index]), offset);  // Q10
        coslsp = add(costable[index], intround(L_shl(a0, 6)));            // Q15 cos((double)PI*lsp[2*n-2])

        c = coslsp;                                                    // Q14 c = 2. * cos((double)PI*lsp[2*n-2])

        for(i = 2*n; i >= 2; i--) {
            L_Extract(f[i-1], &hi, &lo);

            f[i] = L_add(f[i], f[i-2]);                                 // Q23 f[i] += f[i-2]
            a0 = Mpy_32_16(hi, lo, c);                                  // Q22
            f[i] = L_sub(f[i], L_shl(a0,1));                            // Q23 f[i] += f[i-2] - c*f[i-1];
        }
        f[1] = L_msu(f[1], c, 256);                                    // Q23 f[1] -= c;
    }

    return;
}

void Post_Process(
  PopStatus *handle,
  Word16 signal[],    /* input/output signal */
  Word16 lg)          /* length of signal    */
{
  Word16 i, x2;
  Word32 L_tmp;

  for(i=0; i<lg; i++)
  {
     x2 = handle->x1;
     handle->x1 = handle->x0;
     handle->x0 = signal[i];

     /*  y[i] = b[0]*x[i]   + b[1]*x[i-1]   + b[2]*x[i-2]    */
     /*                     + a[1]*y[i-1] + a[2] * y[i-2];      */

     L_tmp     = Mpy_32_16(handle->y1_hi, handle->y1_lo, a100[1]);
     L_tmp     = L_add(L_tmp, Mpy_32_16(handle->y2_hi, handle->y2_lo, a100[2]));
     L_tmp     = L_mac(L_tmp, handle->x0, b100[0]);
     L_tmp     = L_mac(L_tmp, handle->x1, b100[1]);
     L_tmp     = L_mac(L_tmp, x2, b100[2]);
     L_tmp     = L_shl(L_tmp, 2);      /* Q29 --> Q31 (Q13 --> Q15) */

     /* Multiplication by two of output speech with saturation. */
     signal[i] = round(L_shl(L_tmp, 1));

     handle->y2_hi = handle->y1_hi;
     handle->y2_lo = handle->y1_lo;
     L_Extract(L_tmp, &(handle->y1_hi), &(handle->y1_lo));
  }
  return;
}

void Post_Process(
  int16_t signal[],    /* input/output signal */
  int16_t lg)          /* length of signal    */
{
  int16_t i, x2;
  int32_t L_tmp;

  for(i=0; i<lg; i++)
  {
     x2 = x1;
     x1 = x0;
     x0 = signal[i];

     /*  y[i] = b[0]*x[i]   + b[1]*x[i-1]   + b[2]*x[i-2]    */
     /*                     + a[1]*y[i-1] + a[2] * y[i-2];      */

     L_tmp     = Mpy_32_16(y1_hi, y1_lo, a100[1]);
     L_tmp     = L_add(L_tmp, Mpy_32_16(y2_hi, y2_lo, a100[2]));
     L_tmp     = L_mac(L_tmp, x0, b100[0]);
     L_tmp     = L_mac(L_tmp, x1, b100[1]);
     L_tmp     = L_mac(L_tmp, x2, b100[2]);
     L_tmp     = L_shl(L_tmp, 2);      /* Q29 --> Q31 (Q13 --> Q15) */

     /* Multiplication by two of output speech with saturation. */
     signal[i] = _round(L_shl(L_tmp, 1));

     y2_hi = y1_hi;
     y2_lo = y1_lo;
     L_Extract(L_tmp, &y1_hi, &y1_lo);
  }
  return;
}

void Get_wegt(
  Word16 flsp[],    /* (i) Q13 : M LSP parameters  */
  Word16 wegt[]     /* (o) Q11->norm : M weighting coefficients */
)
{
  Word16 i;
  Word16 tmp;
  Word32 L_acc;
  Word16 sft;
  Word16 buf[M]; /* in Q13 */


  buf[0] = sub( flsp[1], (PI04+8192) );           /* 8192:1.0(Q13) */

  for ( i = 1 ; i < M-1 ; i++ ) {
    tmp = sub( flsp[i+1], flsp[i-1] );
    buf[i] = sub( tmp, 8192 );
  }

  buf[M-1] = sub( (PI92-8192), flsp[M-2] );

  /* */
  for ( i = 0 ; i < M ; i++ ) {
    if ( buf[i] > 0 ){
      wegt[i] = 2048;                    /* 2048:1.0(Q11) */
    }
    else {
      L_acc = L_mult( buf[i], buf[i] );           /* L_acc in Q27 */
      tmp = extract_h( L_shl( L_acc, 2 ) );       /* tmp in Q13 */

      L_acc = L_mult( tmp, CONST10 );             /* L_acc in Q25 */
      tmp = extract_h( L_shl( L_acc, 2 ) );       /* tmp in Q11 */

      wegt[i] = add( tmp, 2048 );                 /* wegt in Q11 */
    }
  }

  /* */
  L_acc = L_mult( wegt[4], CONST12 );             /* L_acc in Q26 */
  wegt[4] = extract_h( L_shl( L_acc, 1 ) );       /* wegt in Q11 */

  L_acc = L_mult( wegt[5], CONST12 );             /* L_acc in Q26 */
  wegt[5] = extract_h( L_shl( L_acc, 1 ) );       /* wegt in Q11 */

  /* wegt: Q11 -> normalized */
  tmp = 0;
  for ( i = 0; i < M; i++ ) {
    if ( sub(wegt[i], tmp) > 0 ) {
      tmp = wegt[i];
    }
  }

  sft = norm_s(tmp);
  for ( i = 0; i < M; i++ ) {
    wegt[i] = shl(wegt[i], sft);                  /* wegt in Q(11+sft) */
  }

  return;
}

/*-----------------------------------------------------*
 * Function Autocorr()                                 *
 *                                                     *
 *   Compute autocorrelations of signal with windowing *
 *                                                     *
 *-----------------------------------------------------*/
void Autocorr(
  Word16 x[],      /* (i)    : Input signal                      */
  Word16 m,        /* (i)    : LPC order                         */
  Word16 r_h[],    /* (o)    : Autocorrelations  (msb)           */
  Word16 r_l[]     /* (o)    : Autocorrelations  (lsb)           */
)
{
  Word16 i, j, norm;
  Word16 y[L_WINDOW];
  Word32 sum;

  extern Flag Overflow;

  /* Windowing of signal */

  for(i=0; i<L_WINDOW; i++)
  {
    y[i] = mult_r(x[i], hamwindow[i]);
  }

  /* Compute r[0] and test for overflow */

  do {
    Overflow = 0;
    sum = 1;                   /* Avoid case of all zeros */
    for(i=0; i<L_WINDOW; i++)
      sum = L_mac(sum, y[i], y[i]);

    /* If overflow divide y[] by 4 */

    if(Overflow != 0)
    {
      for(i=0; i<L_WINDOW; i++)
      {
        y[i] = shr(y[i], 2);
      }
    }
  }while (Overflow != 0);

  /* Normalization of r[0] */

  norm = norm_l(sum);
  sum  = L_shl(sum, norm);
  L_Extract(sum, &r_h[0], &r_l[0]);     /* Put in DPF format (see oper_32b) */

  /* r[1] to r[m] */

  for (i = 1; i <= m; i++)
  {
    sum = 0;
    for(j=0; j<L_WINDOW-i; j++)
      sum = L_mac(sum, y[j], y[j+i]);

    sum = L_shl(sum, norm);
    L_Extract(sum, &r_h[i], &r_l[i]);
  }
  return;
}

void Corr_xy2(
      Word16 xn[],           /* (i) Q0  :Target vector.                  */
      Word16 y1[],           /* (i) Q0  :Adaptive codebook.              */
      Word16 y2[],           /* (i) Q12 :Filtered innovative vector.     */
      Word16 g_coeff[],      /* (o) Q[exp]:Correlations between xn,y1,y2 */
      Word16 exp_g_coeff[]   /* (o)       :Q-format of g_coeff[]         */
)
{
      Word16   i,exp;
      Word16   exp_y2y2,exp_xny2,exp_y1y2;
      Word16   y2y2,    xny2,    y1y2;
      Word32   L_acc;
      Word16   scaled_y2[L_SUBFR];       /* Q9 */

      /*------------------------------------------------------------------*
       * Scale down y2[] from Q12 to Q9 to avoid overflow                 *
       *------------------------------------------------------------------*/
      for(i=0; i<L_SUBFR; i++) {
         scaled_y2[i] = shr(y2[i], 3);        }

      /* Compute scalar product <y2[],y2[]> */
      L_acc = 1;                       /* Avoid case of all zeros */
      for(i=0; i<L_SUBFR; i++)
         L_acc = L_mac(L_acc, scaled_y2[i], scaled_y2[i]);    /* L_acc:Q19 */

      exp      = norm_l(L_acc);
      y2y2     = round( L_shl(L_acc, exp) );
      exp_y2y2 = add(exp, 19-16);                          /* Q[19+exp-16] */

      g_coeff[2]     = y2y2;
      exp_g_coeff[2] = exp_y2y2;

      /* Compute scalar product <xn[],y2[]> */
      L_acc = 1;                       /* Avoid case of all zeros */
      for(i=0; i<L_SUBFR; i++)
         L_acc = L_mac(L_acc, xn[i], scaled_y2[i]);           /* L_acc:Q10 */

      exp      = norm_l(L_acc);
      xny2     = round( L_shl(L_acc, exp) );
      exp_xny2 = add(exp, 10-16);                          /* Q[10+exp-16] */

      g_coeff[3]     = negate(xny2);
      exp_g_coeff[3] = sub(exp_xny2,1);                   /* -2<xn,y2> */

      /* Compute scalar product <y1[],y2[]> */
      L_acc = 1;                       /* Avoid case of all zeros */
      for(i=0; i<L_SUBFR; i++)
         L_acc = L_mac(L_acc, y1[i], scaled_y2[i]);           /* L_acc:Q10 */

      exp      = norm_l(L_acc);
      y1y2     = round( L_shl(L_acc, exp) );
      exp_y1y2 = add(exp, 10-16);                          /* Q[10+exp-16] */

      g_coeff[4]     = y1y2;
      exp_g_coeff[4] = sub(exp_y1y2,1);    ;                /* 2<y1,y2> */

      return;
}

/*-------------------------------------------------------------------*
* Function  set_sign()                                              *
* ~~~~~~~~~~~~~~~~~~~~                                              *
* Set the sign of each pulse position.                              *
*-------------------------------------------------------------------*/
static void set_sign(
  Word16 fac_cn,     /* (i) Q15: residual weight for sign determination */
  Word16 cn[],       /* (i) Q0 : residual after long term prediction    */
  Word16 dn[],       /* (i) Q0 : correlation between target and h[]     */
  Word16 sign[],     /* (o) Q15: sign vector (sign of each position)    */
  Word16 inv_sign[], /* (o) Q15: inverse of sign[]                      */
  Word16 pos_max[],  /* (o)    : pos of max of correlation              */
  Word32 corr[]      /* (o)    : correlation of each track              */
)
{
    Word16 i, k, pos, k_cn, k_dn, val;
    Word32 s, max;

    /* calculate energy for normalization of cn[] and dn[] */
    s = 0;
    for (i=0; i<L_SUBFR; i++) s = L_mac(s, cn[i], cn[i]);
    if (s < 512) s = 512;
    s = Inv_sqrt(s);
    k_cn = extract_h(L_shl(s, 5));     /* k_cn = 11..23170 */
    k_cn = mult(k_cn, fac_cn);

    s = 0;
    for (i=0; i<L_SUBFR; i++) s = L_mac(s, dn[i], dn[i]);
    if (s < 512) s = 512;
    s = Inv_sqrt(s);
    k_dn = extract_h(L_shl(s, 5));     /* k_dn = 11..23170 */

    /* set sign according to en[] = k_cn*cn[] + k_dn*dn[]    */

    /* find position of maximum of correlation in each track */
    for (k=0; k<NB_TRACK; k++) {
        max = -1;
        for (i=k; i<L_SUBFR; i+=STEP) {
            val = dn[i];
            s = L_mac(L_mult(k_cn, cn[i]), k_dn, val);
            if (s >= 0) {
                sign[i] = 32767L;         /* sign = +1 (Q15) */
                inv_sign[i] = -32768L;
            }
            else {
                sign[i] = -32768L;        /* sign = -1 (Q15) */
                inv_sign[i] = 32767L;
                val = negate(val);
            }
            dn[i] = val;      /* modify dn[] according to the fixed sign */
            s = L_abs(s);
            if (s > max) {
                max = s;
                pos = i;
            }
        }
        pos_max[k] = pos;
        corr[k] = max;
    }

    return;
}

void update_exc_err(
 Word32 *L_exc_err,
 Word16 gain_pit,      /* (i) pitch gain */
 Word16 T0             /* (i) integer part of pitch delay */
)
 {

    Word16 i, zone1, zone2, n;
    Word32 L_worst, L_temp, L_acc;
    Word16 hi, lo;

    L_worst = -1L;
    n = sub(T0, L_SUBFR);

    if(n < 0) {
        L_Extract(L_exc_err[0], &hi, &lo);
        L_temp = Mpy_32_16(hi, lo, gain_pit);
        L_temp = L_shl(L_temp, 1);
        L_temp = L_add(0x00004000L, L_temp);
        L_acc = L_sub(L_temp, L_worst);
        if(L_acc > 0L) {
                L_worst = L_temp;
        }
        L_Extract(L_temp, &hi, &lo);
        L_temp = Mpy_32_16(hi, lo, gain_pit);
        L_temp = L_shl(L_temp, 1);
        L_temp = L_add(0x00004000L, L_temp);
        L_acc = L_sub(L_temp, L_worst);
        if(L_acc > 0L) {
                L_worst = L_temp;
        }
    }

    else {

        zone1 = tab_zone[n];

        i = sub(T0, 1);
        zone2 = tab_zone[i];

        for(i = zone1; i <= zone2; i++) {
                L_Extract(L_exc_err[i], &hi, &lo);
                L_temp = Mpy_32_16(hi, lo, gain_pit);
                L_temp = L_shl(L_temp, 1);
                L_temp = L_add(0x00004000L, L_temp);
                L_acc = L_sub(L_temp, L_worst);
                if(L_acc > 0L) L_worst = L_temp;
        }
    }

    for(i=3; i>=1; i--) {
        L_exc_err[i] = L_exc_err[i-1];
    }
    L_exc_err[0] = L_worst;

    return;
}

/*-------------------------------------------------------------------*
 * Function  Qua_Sidgain                                             *
 *           ~~~~~~~~~~~                                             *
 *-------------------------------------------------------------------*/
void Qua_Sidgain(
  Word16 *ener,     /* (i)   array of energies                   */
  Word16 *sh_ener,  /* (i)   corresponding scaling factors       */
  Word16 nb_ener,   /* (i)   number of energies or               */
  Word16 *enerq,    /* (o)   decoded energies in dB              */
  Word16 *idx       /* (o)   SID gain quantization index         */
)
{
  Word16 i;
  Word32 L_x;
  Word16 sh1, temp;
  Word16 hi, lo;
  Word32 L_acc;
  
  if(nb_ener == 0) {
    /* Quantize energy saved for frame erasure case                */
    /* L_x = average_ener                                          */
    L_acc = L_deposit_l(*ener);
    L_acc = L_shl(L_acc, *sh_ener); /* >> if *sh_ener < 0 */
    L_Extract(L_acc, &hi, &lo);
    L_x = Mpy_32_16(hi, lo, fact[0]);
    sh1 = 0;
  }
  else {
    
    /*
     * Compute weighted average of energies
     * ener[i] = enerR[i] x 2**sh_ener[i]
     * L_x = k[nb_ener] x SUM(i=0->nb_ener-1) enerR[i]
     * with k[nb_ener] =  fact_ener / nb_ener x L_FRAME x nbAcf
     */
    sh1 = sh_ener[0];
    for(i=1; i<nb_ener; i++) {
      if(sh_ener[i] < sh1) sh1 = sh_ener[i];
    }
    sh1 = add(sh1, (16-marg[nb_ener]));
    L_x = 0L;
    for(i=0; i<nb_ener; i++) {
      temp = sub(sh1, sh_ener[i]);
      L_acc = L_deposit_l(ener[i]);
      L_acc = L_shl(L_acc, temp);
      L_x = L_add(L_x, L_acc);
    }
    L_Extract(L_x, &hi, &lo);
    L_x = Mpy_32_16(hi, lo, fact[i]);
  }
  
  *idx = Quant_Energy(L_x, sh1, enerq);
  
  return;
}

void Post_Process(
  Word16 signal[],    /* input/output signal */
  Word16 lg)          /* length of signal    */
{
  Word16 i, x2;
  Word32 L_tmp;
	
	Word16 y2_hi, y2_lo, y1_hi, y1_lo, x0, x1;

	y2_hi = pg729dec->ppost_pro->y2_hi;
	y2_lo = pg729dec->ppost_pro->y2_lo;
	y1_hi = pg729dec->ppost_pro->y1_hi;
	y1_lo = pg729dec->ppost_pro->y1_lo;
	x0 = pg729dec->ppost_pro->x0;
	x1 = pg729dec->ppost_pro->x1;
	
  for(i=0; i<lg; i++)
  {
     x2 = x1;
     x1 = x0;
     x0 = signal[i];

     /*  y[i] = b[0]*x[i]   + b[1]*x[i-1]   + b[2]*x[i-2]    */
     /*                     + a[1]*y[i-1] + a[2] * y[i-2];      */

     L_tmp     = Mpy_32_16(y1_hi, y1_lo, a100[1]);
     L_tmp     = L_add(L_tmp, Mpy_32_16(y2_hi, y2_lo, a100[2]));
     L_tmp     = L_mac(L_tmp, x0, b100[0]);
     L_tmp     = L_mac(L_tmp, x1, b100[1]);
     L_tmp     = L_mac(L_tmp, x2, b100[2]);
     L_tmp     = L_shl(L_tmp, 2);      /* Q29 --> Q31 (Q13 --> Q15) */

     /* Multiplication by two of output speech with saturation. */
     signal[i] = round(L_shl(L_tmp, 1));

     y2_hi = y1_hi;
     y2_lo = y1_lo;
     L_Extract(L_tmp, &y1_hi, &y1_lo);
  }
  
	pg729dec->ppost_pro->y2_hi = y2_hi;
	pg729dec->ppost_pro->y2_lo = y2_lo;
	pg729dec->ppost_pro->y1_hi = y1_hi;
	pg729dec->ppost_pro->y1_lo = y1_lo;
	pg729dec->ppost_pro->x0 = x0;
	pg729dec->ppost_pro->x1 = x1;
	
  
  return;
}

void rmlt_coefs_to_samples(int16_t coefs[],
                           int16_t old_samples[],
                           int16_t out_samples[],
                           int dct_length,
                           int16_t mag_shift)
{
    int i;
    int half_dct_length;
    int last;
    int16_t new_samples[MAX_DCT_LENGTH];
    const int16_t *win;
    int32_t sum;

    half_dct_length = dct_length >> 1;

    /* Perform a Type IV (inverse) DCT on the coefficients */
    dct_type_iv_s(coefs, new_samples, dct_length);

    if (mag_shift > 0)
    {
        for (i = 0;  i < dct_length;  i++)
            new_samples[i] = shr(new_samples[i], mag_shift);
    }
    else if (mag_shift < 0)
    {
        mag_shift = negate(mag_shift);
        for (i = 0;  i < dct_length;  i++)
            new_samples[i] = shl(new_samples[i], mag_shift);
    }

    win = (dct_length == DCT_LENGTH)  ?  rmlt_to_samples_window  :  max_rmlt_to_samples_window;
    last = half_dct_length - 1;
    for (i = 0;  i < half_dct_length;  i++)
    {
        /* Get the first half of the windowed samples */
        sum = L_mult(win[i], new_samples[last - i]);
        sum = L_mac(sum, win[dct_length - i - 1], old_samples[i]);
        out_samples[i] = xround(L_shl(sum, 2));
        /* Get the second half of the windowed samples */
        sum = L_mult(win[half_dct_length + i], new_samples[i]);
        sum = L_mac(sum, negate(win[last - i]), old_samples[last - i]);
        out_samples[half_dct_length + i] = xround(L_shl(sum, 2));
    }

    /* Save the second half of the new samples for
       next time, when they will be the old samples. */
    vec_copyi16(old_samples, &new_samples[half_dct_length], half_dct_length);
}

Word32 Div_32(Word32 L_num, Word16 denom_hi, Word16 denom_lo)
{
  Word16 approx, hi, lo, n_hi, n_lo;
  Word32 L_32;


  /* First approximation: 1 / L_denom = 1/denom_hi */

  approx = div_s( (Word16)0x3fff, denom_hi);    /* result in Q14 */
                                                /* Note: 3fff = 0.5 in Q15 */

  /* 1/L_denom = approx * (2.0 - L_denom * approx) */

  L_32 = Mpy_32_16(denom_hi, denom_lo, approx); /* result in Q30 */


  L_32 = L_sub( (Word32)0x7fffffffL, L_32);      /* result in Q30 */

  L_Extract(L_32, &hi, &lo);

  L_32 = Mpy_32_16(hi, lo, approx);             /* = 1/L_denom in Q29 */

  /* L_num * (1/L_denom) */

  L_Extract(L_32, &hi, &lo);
  L_Extract(L_num, &n_hi, &n_lo);
  L_32 = Mpy_32(n_hi, n_lo, hi, lo);            /* result in Q29   */
  L_32 = L_shl(L_32, 2);                        /* From Q29 to Q31 */

  return( L_32 );
}

void Pre_Process(
  Word16 signal[],    /* input/output signal */
  Word16 lg)          /* length of signal    */
{
  Word16 i, x2;
  Word32 L_tmp;

  for(i=0; i<lg; i++)
  {
     x2 = x1;
     x1 = x0;
     x0 = signal[i];

     /*  y[i] = b[0]*x[i]/2 + b[1]*x[i-1]/2 + b140[2]*x[i-2]/2  */
     /*                     + a[1]*y[i-1] + a[2] * y[i-2];      */

     L_tmp     = Mpy_32_16(y1_hi, y1_lo, a140[1]);
     L_tmp     = L_add(L_tmp, Mpy_32_16(y2_hi, y2_lo, a140[2]));
     L_tmp     = L_mac(L_tmp, x0, b140[0]);
     L_tmp     = L_mac(L_tmp, x1, b140[1]);
     L_tmp     = L_mac(L_tmp, x2, b140[2]);
     L_tmp     = L_shl(L_tmp, 3);      /* Q28 --> Q31 (Q12 --> Q15) */
     signal[i] = round(L_tmp);

     y2_hi = y1_hi;
     y2_lo = y1_lo;
     L_Extract(L_tmp, &y1_hi, &y1_lo);
  }
  return;
}