vad.c

GSM中半速率语音编解码源码

  /*** Test if prediction error is smaller than threshold ***/

  swTemp = sub(swPredErr, 1464);

  if (swTemp < 0)
    *pswTone = 1;

}

/****************************************************************************
 *
 *     FUNCTION:  threshold_adaptation
 *
 *     VERSION:   1.2
 *
 *     PURPOSE:   Evaluates the secondary VAD decision.  If speech is not
 *                present then the noise model rvad and adaptive threshold
 *                thvad are updated.
 *
 *     INPUTS:    swStat        flag to indicate spectral stationarity
 *                swPtch        flag to indicate a periodic signal component
 *                swTone        flag to indicate a tone signal component
 *                pswRav1[0..8] ACF obtained from l_av1
 *                swNormRav1    r_av1 scaling factor
 *                swM_pvad      mantissa of filtered signal energy
 *                swE_pvad      exponent of filtered signal energy
 *                swM_acf0      mantissa of signal frame energy
 *                swE_acf0      exponent of signal frame energy
 *
 *     OUTPUTS:   pswRvad[0..8] autocorrelated adaptive filter coefficients
 *                pswNormRvad   rvad scaling factor
 *                pswM_thvad    mantissa of decision threshold
 *                pswE_thvad    exponent of decision threshold
 *
 ***************************************************************************/

void   threshold_adaptation(Shortword swStat,
                                   Shortword swPtch,
                                   Shortword swTone,
                                   Shortword pswRav1[],
                                   Shortword swNormRav1,
                                   Shortword swM_pvad,
                                   Shortword swE_pvad,
                                   Shortword swM_acf0,
                                   Shortword swE_acf0,
                                   Shortword pswRvad[],
                                   Shortword *pswNormRvad,
                                   Shortword *pswM_thvad,
                                   Shortword *pswE_thvad)
{

/*_________________________________________________________________________
 |                                                                         |
 |                            Automatic Variables                          |
 |_________________________________________________________________________|
*/

  Longword
         L_temp;

  Shortword
         swTemp,
         swComp,
         swComp2,
         swM_temp,
         swE_temp;

  int
         i;


/*_________________________________________________________________________
 |                                                                         |
 |                              Executable Code                            |
 |_________________________________________________________________________|
*/

  swComp = 0;

  /*** Test if acf0 < pth; if yes set thvad to plev ***/

  if (swE_acf0 < E_PTH)
    swComp = 1;
  if ((swE_acf0 == E_PTH) && (swM_acf0 < M_PTH))
    swComp = 1;

  if (swComp == 1)
  {
    *pswE_thvad = E_PLEV;
    *pswM_thvad = M_PLEV;

    return;
  }


  /*** Test if an adaption is required ***/

  if (swPtch == 1)
    swComp = 1;
  if (swStat == 0)
    swComp = 1;
  if (swTone == 1)
    swComp = 1;

  if (swComp == 1)
  {
    swAdaptCount = 0;
    return;
  }


  /*** Increment adaptcount ***/

  swAdaptCount = add(swAdaptCount, 1);
  if (swAdaptCount <= 8)
    return;


  /*** computation of thvad-(thvad/dec) ***/

  *pswM_thvad = sub(*pswM_thvad, shr(*pswM_thvad, 5));

  if (*pswM_thvad < 0x4000)
  {
    *pswM_thvad = shl(*pswM_thvad, 1);
    *pswE_thvad = sub(*pswE_thvad, 1);
  }


  /*** computation of pvad*fac ***/

  L_temp = L_mult(swM_pvad, 20889);
  L_temp = L_shr(L_temp, 15);
  swE_temp = add(swE_pvad, 1);

  if (L_temp > 0x7fffL)
  {
    L_temp = L_shr(L_temp, 1);
    swE_temp = add(swE_temp, 1);
  }
  swM_temp = extract_l(L_temp);


  /*** test if thvad < pavd*fac ***/

  if (*pswE_thvad < swE_temp)
    swComp = 1;

  if ((*pswE_thvad == swE_temp) && (*pswM_thvad < swM_temp))
    swComp = 1;


  /*** compute minimum(thvad+(thvad/inc), pvad*fac) when comp = 1 ***/

  if (swComp == 1)
  {

    /*** compute thvad + (thvad/inc) ***/

    L_temp = L_add(L_deposit_l(*pswM_thvad),L_deposit_l(shr(*pswM_thvad, 4)));

    if (L_temp > 0x7fffL)
    {
      *pswM_thvad = extract_l(L_shr(L_temp, 1));
      *pswE_thvad = add(*pswE_thvad, 1);
    }
    else
      *pswM_thvad = extract_l(L_temp);

    swComp2 = 0;

    if (swE_temp < *pswE_thvad)
      swComp2 = 1;

    if ((swE_temp == *pswE_thvad) && (swM_temp < *pswM_thvad))
      swComp2 = 1;

    if (swComp2 == 1)
    {
      *pswE_thvad = swE_temp;
      *pswM_thvad = swM_temp;
    }
  }


  /*** compute pvad + margin ***/

  if (swE_pvad == E_MARGIN)
  {
    L_temp = L_add(L_deposit_l(swM_pvad), L_deposit_l(M_MARGIN));
    swM_temp = extract_l(L_shr(L_temp, 1));
    swE_temp = add(swE_pvad, 1);
  }
  else
  {
    if (swE_pvad > E_MARGIN)
    {
      swTemp = sub(swE_pvad, E_MARGIN);
      swTemp = shr(M_MARGIN, swTemp);
      L_temp = L_add(L_deposit_l(swM_pvad), L_deposit_l(swTemp));

      if (L_temp > 0x7fffL)
      {
        swE_temp = add(swE_pvad, 1);
        swM_temp = extract_l(L_shr(L_temp, 1));
      }
      else
      {
        swE_temp = swE_pvad;
        swM_temp = extract_l(L_temp);
      }
    }
    else
    {
      swTemp = sub(E_MARGIN, swE_pvad);
      swTemp = shr(swM_pvad, swTemp);
      L_temp = L_add(L_deposit_l(M_MARGIN), L_deposit_l(swTemp));

      if (L_temp > 0x7fffL)
      {
        swE_temp = add(E_MARGIN, 1);
        swM_temp = extract_l(L_shr(L_temp, 1));
      }
      else
      {
        swE_temp = E_MARGIN;
        swM_temp = extract_l(L_temp);
      }
    }
  }

  /*** Test if thvad > pvad + margin ***/

  swComp = 0;

  if (*pswE_thvad > swE_temp)
    swComp = 1;

  if ((*pswE_thvad == swE_temp) && (*pswM_thvad > swM_temp))
    swComp = 1;

  if (swComp == 1)
  {
    *pswE_thvad = swE_temp;
    *pswM_thvad = swM_temp;
  }

  /*** Normalise and retain rvad[0..8] in memory ***/

  *pswNormRvad = swNormRav1;

  for (i = 0; i <= 8; i++)
    pswRvad[i] = pswRav1[i];

  /*** Set adaptcount to adp + 1 ***/

  swAdaptCount = 9;

}

/****************************************************************************
 *
 *     FUNCTION:  vad_decision
 *
 *     VERSION:   1.2
 *
 *     PURPOSE:   Computes the VAD decision based on the comparison of the
 *                floating point representations of pvad and thvad.
 *
 *     INPUTS:    swM_pvad      mantissa of filtered signal energy
 *                swE_pvad      exponent of filtered signal energy
 *                swM_thvad     mantissa of decision threshold
 *                swE_thvad     exponent of decision threshold
 *
 *     OUTPUTS:   pswVvad       vad decision before hangover is added
 *
 ***************************************************************************/

void   vad_decision(Shortword swM_pvad,
                           Shortword swE_pvad,
                           Shortword swM_thvad,
                           Shortword swE_thvad,
                           Shortword *pswVvad)
{

/*_________________________________________________________________________
 |                                                                         |
 |                              Executable Code                            |
 |_________________________________________________________________________|
*/

  *pswVvad = 0;

  if (swE_pvad > swE_thvad)
    *pswVvad = 1;
  if ((swE_pvad == swE_thvad) && (swM_pvad > swM_thvad))
    *pswVvad = 1;

}

/****************************************************************************
 *
 *     FUNCTION:  vad_hangover
 *
 *     VERSION:   1.2
 *
 *     PURPOSE:   Computes the final VAD decision for the current frame
 *                being processed.
 *
 *     INPUTS:    swVvad        vad decision before hangover is added
 *
 *     OUTPUTS:   pswVadFlag    vad decision after hangover is added
 *
 ***************************************************************************/

void   vad_hangover(Shortword swVvad,
                           Shortword *pswVadFlag)
{

/*_________________________________________________________________________
 |                                                                         |
 |                              Executable Code                            |
 |_________________________________________________________________________|
*/

  if (swVvad == 1)
    swBurstCount = add(swBurstCount, 1);
  else
    swBurstCount = 0;

  if (swBurstCount >= 3)
  {
    swHangCount = 5;
    swBurstCount = 3;
  }

  *pswVadFlag = swVvad;

  if (swHangCount >= 0)
  {
    *pswVadFlag = 1;
    swHangCount = sub(swHangCount, 1);
  }

}

/****************************************************************************
 *
 *     FUNCTION:  periodicity_update
 *
 *     VERSION:   1.2
 *
 *     PURPOSE:   Computes the ptch flag needed for the threshold
 *                adaptation decision for the next frame.
 *
 *     INPUTS:    pswLags[0..3]    speech encoder long term predictor lags
 *
 *     OUTPUTS:   pswPtch          Boolean voiced / unvoiced decision
 *
 ***************************************************************************/

void   periodicity_update(Shortword pswLags[4],
                                 Shortword *pswPtch)
{

/*_________________________________________________________________________
 |                                                                         |
 |                            Automatic Variables                          |
 |_________________________________________________________________________|
*/

  Shortword
         swMinLag,
         swMaxLag,
         swSmallLag,
         swLagCount,
         swTemp;

  int
         i,
         j;

/*_________________________________________________________________________
 |                                                                         |
 |                              Executable Code                            |
 |_________________________________________________________________________|
*/

  /*** Run loop for No. of sub-segments in the frame ***/

  swLagCount = 0;

  for (i = 0; i <= 3; i++)
  {
    /*** Search the maximum and minimum of consecutive lags ***/

    if (swOldLag > pswLags[i])
    {
      swMinLag = pswLags[i];
      swMaxLag = swOldLag;
    }
    else
    {
      swMinLag = swOldLag;
      swMaxLag = pswLags[i];
    }


    /*** Compute smallag (modulo operation not defined) ***/

    swSmallLag = swMaxLag;

    for (j = 0; j <= 2; j++)
    {
      if (swSmallLag >= swMinLag)
        swSmallLag = sub(swSmallLag, swMinLag);
    }


    /***  Minimum of smallag and minlag - smallag ***/

    swTemp = sub(swMinLag, swSmallLag);

    if (swTemp < swSmallLag)
      swSmallLag = swTemp;

    if (swSmallLag < 2)
      swLagCount = add(swLagCount, 1);


    /*** Save the current LTP lag ***/

    swOldLag = pswLags[i];
  }


  /*** Update the veryoldlagcount and oldlagcount ***/

  swVeryOldLagCount = swOldLagCount;
  swOldLagCount = swLagCount;


  /*** Make ptch decision ready for next frame ***/

  swTemp = add(swOldLagCount, swVeryOldLagCount);

  if (swTemp >= 7)
    *pswPtch = 1;
  else
    *pswPtch = 0;

}