c_g_aver.cpp

实现3GPP的GSM中AMR语音的CODECS。

   if (sub(diff, 5325) > 0)  // 0.65 in Q11
   {
      st->hangVar = add(st->hangVar, 1);
   }
   else
   {
      st->hangVar = 0;
   }

   if (sub(st->hangVar, 10) > 0)
   {
      st->hangCount = 0;  // Speech period, reset hangover variable
   }

   // Compute mix constant (bgMix)
   bgMix = 8192;    // 1 in Q13
   if ((sub(mode, MR67) <= 0) || (sub(mode, MR102) == 0))
      // MR475, MR515, MR59, MR67, MR102
   {
      // if errors and presumed noise make smoothing probability stronger
      if (((((pdfi != 0) && (prev_pdf != 0)) || (bfi != 0) || (prev_bf != 0)) &&
          (sub(voicedHangover, 1) > 0) && (inBackgroundNoise != 0) &&
          ((sub(mode, MR475) == 0) ||
           (sub(mode, MR515) == 0) ||
           (sub(mode, MR59) == 0)) ))
      {
         // bgMix = min(0.25, max(0.0, diff-0.55)) / 0.25;
         tmp_diff = sub(diff, 4506);   // 0.55 in Q13

         // max(0.0, diff-0.55)
         if (tmp_diff > 0)
         {
            tmp1 = tmp_diff;
         }
         else
         {
            tmp1 = 0;
         }

         // min(0.25, tmp1)
         if (sub(2048, tmp1) < 0)
         {
            bgMix = 8192;
         }
         else
         {
            bgMix = shl(tmp1, 2);
         }
      }
      else
      {
         // bgMix = min(0.25, max(0.0, diff-0.40)) / 0.25;
         tmp_diff = sub(diff, 3277); // 0.4 in Q13

         // max(0.0, diff-0.40)
         if (tmp_diff > 0)
         {
            tmp1 = tmp_diff;
         }
         else
         {
            tmp1 = 0;
         }

         // min(0.25, tmp1)
         if (sub(2048, tmp1) < 0)
         {
            bgMix = 8192;
         }
         else
         {
            bgMix = shl(tmp1, 2);
         }
      }

      if ((sub(st->hangCount, 40) < 0) || (sub(diff, 5325) > 0)) // 0.65 in Q13
      {
         bgMix = 8192;  // disable mix if too short time since
      }

      // Smoothen the cb gain trajectory
      // smoothing depends on mix constant bgMix
      L_sum = L_mult(6554, st->cbGainHistory[2]); // 0.2 in Q15; L_sum in Q17
      for (i = 3; i < L_CBGAINHIST; i++)
      {
         L_sum = L_mac(L_sum, 6554, st->cbGainHistory[i]);
      }
      cbGainMean = pv_round(L_sum);                      // Q1

      // more smoothing in error and bg noise (NB no DFI used  here)
      if (((bfi != 0) || (prev_bf != 0)) && (inBackgroundNoise != 0) &&
          ((sub(mode, MR475) == 0) ||
           (sub(mode, MR515) == 0) ||
           (sub(mode, MR59) == 0)) )
      {
         L_sum = L_mult(4681, st->cbGainHistory[0]); // 0.143 in Q15; L_sum in Q17
         for (i = 1; i < L_CBGAINHIST; i++)
         {
            L_sum = L_mac(L_sum, 4681, st->cbGainHistory[i]);
         }
         cbGainMean = pv_round(L_sum);                   // Q1
      }

      // cbGainMix = bgMix*cbGainMix + (1-bgMix)*cbGainMean;
      L_sum = L_mult(bgMix, cbGainMix);               // L_sum in Q15
      L_sum = L_mac(L_sum, 8192, cbGainMean);
      L_sum = L_msu(L_sum, bgMix, cbGainMean);
      cbGainMix = pv_round(L_shl(L_sum, 2));             // Q1
   }

   st->hangCount = add(st->hangCount, 1);
   return cbGainMix;
}

------------------------------------------------------------------------------
 RESOURCES USED [optional]

 When the code is written for a specific target processor the
 the resources used should be documented below.

 HEAP MEMORY USED: x bytes

 STACK MEMORY USED: x bytes

 CLOCK CYCLES: (cycle count equation for this function) + (variable
                used to represent cycle count for each subroutine
                called)
     where: (cycle count variable) = cycle count for [subroutine
                                     name]

------------------------------------------------------------------------------
 CAUTION [optional]
 [State any special notes, constraints or cautions for users of this function]

------------------------------------------------------------------------------
*/

Word16 Cb_gain_average(
    Cb_gain_averageState *st, /* i/o : State variables for CB gain averaging */
    enum Mode mode,           /* i   : AMR mode                              */
    Word16 gain_code,         /* i   : CB gain                            Q1 */
    Word16 lsp[],             /* i   : The LSP for the current frame     Q15 */
    Word16 lspAver[],         /* i   : The average of LSP for 8 frames   Q15 */
    Word16 bfi,               /* i   : bad frame indication flag             */
    Word16 prev_bf,           /* i   : previous bad frame indication flag    */
    Word16 pdfi,              /* i   : potential degraded bad frame ind flag */
    Word16 prev_pdf,          /* i   : prev pot. degraded bad frame ind flag */
    Word16 inBackgroundNoise, /* i   : background noise decision             */
    Word16 voicedHangover,    /* i   : # of frames after last voiced frame   */
    Flag   *pOverflow
)
{
    Word16 i;
    Word16 cbGainMix;
    Word16 diff;
    Word16 tmp_diff;
    Word16 bgMix;
    Word16 cbGainMean;
    Word32 L_sum;
    Word16 tmp[M];
    Word16 tmp1;
    Word16 tmp2;
    Word16 shift1;
    Word16 shift2;
    Word16 shift;

    /*---------------------------------------------------------*
     * Compute mixed cb gain, used to make cb gain more        *
     * smooth in background noise for modes 5.15, 5.9 and 6.7  *
     * states that needs to be updated by all                  *
     *---------------------------------------------------------*/

    /* set correct cbGainMix for MR74, MR795, MR122 */
    cbGainMix = gain_code;

    /*-------------------------------------------------------*
     *   Store list of CB gain needed in the CB gain         *
     *   averaging                                           *
     *-------------------------------------------------------*/
    for (i = 0; i < (L_CBGAINHIST - 1); i++)
    {
        st->cbGainHistory[i] = st->cbGainHistory[i+1];
    }
    st->cbGainHistory[L_CBGAINHIST-1] = gain_code;

    diff = 0;

    /* compute lsp difference */
    for (i = 0; i < M; i++)
    {
        tmp1 = abs_s(sub(*(lspAver + i), *(lsp + i), pOverflow));
        /* Q15      */
        shift1 = sub(norm_s(tmp1), 1, pOverflow);       /* Qn       */
        tmp1 = shl(tmp1, shift1, pOverflow);            /* Q15+Qn   */
        shift2 = norm_s(*(lspAver + i));                /* Qm       */
        tmp2 = shl(*(lspAver + i), shift2, pOverflow);  /* Q15+Qm   */
        tmp[i] = div_s(tmp1, tmp2);        /* Q15+(Q15+Qn)-(Q15+Qm) */

        shift = 2 + shift1 - shift2;

        if (shift >= 0)
        {
            *(tmp + i) = shr(*(tmp + i), shift, pOverflow);
            /* Q15+Qn-Qm-Qx=Q13 */
        }
        else
        {
            *(tmp + i) = shl(*(tmp + i), negate(shift), pOverflow);
            /* Q15+Qn-Qm-Qx=Q13 */
        }

        diff = add(diff, *(tmp + i), pOverflow);           /* Q13 */
    }

    /* Compute hangover */

    if (diff > 5325)                /* 0.65 in Q11 */
    {
        st->hangVar += 1;
    }
    else
    {
        st->hangVar = 0;
    }


    if (st->hangVar > 10)
    {
        /* Speech period, reset hangover variable */
        st->hangCount = 0;
    }

    /* Compute mix constant (bgMix) */
    bgMix = 8192;    /* 1 in Q13 */

    if ((mode <= MR67) || (mode == MR102))
        /* MR475, MR515, MR59, MR67, MR102 */
    {
        /* if errors and presumed noise make smoothing probability stronger */

        if (((((pdfi != 0) && (prev_pdf != 0)) || (bfi != 0) ||
                (prev_bf != 0))
                && (voicedHangover > 1)
                && (inBackgroundNoise != 0)
                && ((mode == MR475) || (mode == MR515) ||
                    (mode == MR59))))
        {
            /* bgMix = min(0.25, max(0.0, diff-0.55)) / 0.25; */
            tmp_diff = sub(diff, 4506, pOverflow);   /* 0.55 in Q13 */
        }
        else
        {
            /* bgMix = min(0.25, max(0.0, diff-0.40)) / 0.25; */
            tmp_diff = sub(diff, 3277, pOverflow); /* 0.4 in Q13 */
        }

        /* max(0.0, diff-0.55)  or  */
        /* max(0.0, diff-0.40) */
        if (tmp_diff > 0)
        {
            tmp1 = tmp_diff;
        }
        else
        {
            tmp1 = 0;
        }

        /* min(0.25, tmp1) */
        if (2048 < tmp1)
        {
            bgMix = 8192;
        }
        else
        {
            bgMix = shl(tmp1, 2, pOverflow);
        }

        if ((st->hangCount < 40) || (diff > 5325)) /* 0.65 in Q13 */
        {
            /* disable mix if too short time since */
            bgMix = 8192;
        }

        /* Smoothen the cb gain trajectory  */
        /* smoothing depends on mix constant bgMix */
        L_sum = L_mult(6554, st->cbGainHistory[2], pOverflow);
        /* 0.2 in Q15; L_sum in Q17 */

        for (i = 3; i < L_CBGAINHIST; i++)
        {
            L_sum = L_mac(L_sum, 6554, st->cbGainHistory[i], pOverflow);
        }
        cbGainMean = pv_round(L_sum, pOverflow);               /* Q1 */

        /* more smoothing in error and bg noise (NB no DFI used here) */

        if (((bfi != 0) || (prev_bf != 0)) && (inBackgroundNoise != 0)
                && ((mode == MR475) || (mode == MR515)
                    || (mode == MR59)))
        {
            /* 0.143 in Q15; L_sum in Q17    */
            L_sum = L_mult(4681, st->cbGainHistory[0], pOverflow);
            for (i = 1; i < L_CBGAINHIST; i++)
            {
                L_sum =
                    L_mac(L_sum, 4681, st->cbGainHistory[i], pOverflow);
            }
            cbGainMean = pv_round(L_sum, pOverflow);              /* Q1 */
        }

        /* cbGainMix = bgMix*cbGainMix + (1-bgMix)*cbGainMean; */
        /* L_sum in Q15 */
        L_sum = L_mult(bgMix, cbGainMix, pOverflow);
        L_sum = L_mac(L_sum, 8192, cbGainMean, pOverflow);
        L_sum = L_msu(L_sum, bgMix, cbGainMean, pOverflow);
        cbGainMix = pv_round(L_shl(L_sum, 2, pOverflow), pOverflow);  /* Q1 */
    }

    st->hangCount += 1;

    return (cbGainMix);
}