量化（三）

爲了更好地與draft進行對應，看HM中的反量化部分代碼：

Void TComTrQuant::xDeQuant(Int bitDepth, const TCoeff* pSrc, Int* pDes, Int iWidth, Int iHeight, Int scalingListType )  
{  
    
  const TCoeff* piQCoef   = pSrc;  
  Int*   piCoef    = pDes;  
    
  if ( iWidth > (Int)m_uiMaxTrSize )  
  {  
    iWidth  = m_uiMaxTrSize;  
    iHeight = m_uiMaxTrSize;  
  }  
    
  Int iShift,iAdd,iCoeffQ;  
  UInt uiLog2TrSize = g_aucConvertToBit[ iWidth ] + 2;  
  
  Int iTransformShift = MAX_TR_DYNAMIC_RANGE - bitDepth - uiLog2TrSize;  
  
  iShift = QUANT_IQUANT_SHIFT - QUANT_SHIFT - iTransformShift; //!< draft (8-240)、(8-241)  
  //! iShift = bitDepth + uiLog2 - 5 - 4  
  //! 注意，這個結果比draft中多減了個4，這是因爲此時scaling_list_enable_flag默認情況下爲0，則m[x][y]爲16，比較  
  //! 式(8-250)可知代碼中並未乘以m[x][y]，而iShift比式子小了4（相當於總結果少除以16），故代碼與draft兩者是一致的  
  
  TCoeff clipQCoef;  
  const Int bitRange = min( 15, ( Int )( 12 + uiLog2TrSize + bitDepth - m_cQP.m_iPer) );  
  const Int levelLimit = 1 << bitRange;  
  
  if(getUseScalingList()) //!< 默認情況下爲false  
  {  
    iShift += 4;  
    if(iShift > m_cQP.m_iPer)  
    {  
      iAdd = 1 << (iShift - m_cQP.m_iPer - 1);  
    }  
    else  
    {  
      iAdd = 0;  
    }  
    Int *piDequantCoef = getDequantCoeff(scalingListType,m_cQP.m_iRem,uiLog2TrSize-2);  
  
    if(iShift > m_cQP.m_iPer)  
    {  
      for( Int n = 0; n < iWidth*iHeight; n++ )  
      {  
        clipQCoef = Clip3( -32768, 32767, piQCoef[n] );  
        iCoeffQ = ((clipQCoef * piDequantCoef[n]) + iAdd ) >> (iShift -  m_cQP.m_iPer);  
        piCoef[n] = Clip3(-32768,32767,iCoeffQ);  
      }  
    }  
    else  
    {  
      for( Int n = 0; n < iWidth*iHeight; n++ )  
      {  
        clipQCoef = Clip3( -levelLimit, levelLimit - 1, piQCoef[n] );  
        iCoeffQ = (clipQCoef * piDequantCoef[n]) << (m_cQP.m_iPer - iShift);  
        piCoef[n] = Clip3(-32768,32767,iCoeffQ);  
      }  
    }  
  }  
  else //!< draft 8.6.3 (8-250)  
  {  
    iAdd = 1 << (iShift-1);  
    Int scale = g_invQuantScales[m_cQP.m_iRem] << m_cQP.m_iPer; //!< levelScale[qP % 6] << (qP / 6)  
  
    for( Int n = 0; n < iWidth*iHeight; n++ )  
    {  
      clipQCoef = Clip3( -32768, 32767, piQCoef[n] ); //!< TransCoeffLevel[xT][yT][cIdx]  
      iCoeffQ = ( clipQCoef * scale + iAdd ) >> iShift; //!< d[x][y]  
      piCoef[n] = Clip3(-32768,32767,iCoeffQ);  
    }  
  }  
}