VVC普通量化

总结一下VVC普通量化部分

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主体函数

void Quant::quant(TransformUnit &tu, const ComponentID &compID, const CCoeffBuf &pSrc, TCoeff &uiAbsSum, const QpParam &cQP, const Ctx& ctx)

主要用到的变量：

const CCoeffBuf &piCoef   = pSrc;   //变换系数
        CoeffBuf   piQCoef  = tu.getCoeffs(compID);  //量化后系数

//根据缩放类型获取量化系数矩阵
    int *piQuantCoeff = getQuantCoeff(scalingListType, cQP.rem(useTransformSkip), uiLog2TrWidth, uiLog2TrHeight);

//获取默认量化系数 MF值
    // cQP.per表示floor(QP/6)的值
    // cQP.rem表示QP%6的值
    const int defaultQuantisationCoefficient    = g_quantScales[needSqrtAdjustment?1:0][cQP.rem(useTransformSkip)];
    // iTranformShift表示整数DCT变换的缩放因子，该因子和变换尺寸有关
    int iTransformShift = getTransformShift(channelBitDepth, rect.size(), maxLog2TrDynamicRange) + ( needSqrtAdjustment?-1:0);

//计算qbit，QUANT_SHIFT =14,cQP.per=floor(QP/6),qbit=14+floor(QP/6)
    //如果使用的不是变换跳过模式，则再加上DCT系数的缩放因子
    const int iQBits = QUANT_SHIFT + cQP.per(useTransformSkip) + (useTransformSkip ? 0 : iTransformShift);

// 计算f'=f<<(qbit+T)
    const int64_t iAdd = int64_t(tu.cs->slice->isIRAP() ? 171 : 85) << int64_t(iQBits - 9);
    const int qBits8 = iQBits - 8;

//最大系数数目
    const int maxNumberOfCoeffs = lfnstIdx > 0 ? ((( uiWidth == 4 && uiHeight == 4 ) || ( uiWidth == 8 && uiHeight == 8) ) ? 8 : 16) : piQCoef.area();

然后，用for循环遍历块内所有系数，分别对其量化：

for (int uiScanPos = 0; uiScanPos < maxNumberOfCoeffs; uiScanPos++)
    {
      const int uiBlockPos = scan[uiScanPos].idx;//变换系数d
      const TCoeff iLevel   = piCoef.buf[uiBlockPos];//变换系数符号
      const TCoeff iSign    = (iLevel < 0 ? -1: 1);
      // enableScalingLists 表示是否同时完成DCT变换中的伸缩因子的乘法运算
      //表示缩放前的变换系数d * MF
      const int64_t  tmpLevel = (int64_t)abs(iLevel) * (enableScalingLists ? piQuantCoeff[uiBlockPos] : defaultQuantisationCoefficient);
      //根据量化公式得到量化后系数的幅度值(即绝对值)
      const TCoeff quantisedMagnitude = TCoeff((tmpLevel + iAdd ) >> iQBits);   //|l（i，j）|
      deltaU[uiBlockPos] = (TCoeff)((tmpLevel - ((int64_t)quantisedMagnitude<<iQBits) )>> qBits8);

      uiAbsSum += quantisedMagnitude;
      const TCoeff quantisedCoefficient = quantisedMagnitude * iSign;//最终的量化系数

      piQCoef.buf[uiBlockPos] = Clip3<TCoeff>( entropyCodingMinimum, entropyCodingMaximum, quantisedCoefficient );
    } // for n
    if ((tu.cu->bdpcmMode && isLuma(compID)) || (tu.cu->bdpcmModeChroma && isChroma(compID)) )
    {
      fwdResDPCM( tu, compID );
    }
    if( cctx.signHiding() )
    {
      //这就防止了只有一个系数值为1的TUs被测试
      if(uiAbsSum >= 2) //this prevents TUs with only one coefficient of value 1 from being tested
      {
        //只为了最小化失真，不考虑比特率
        xSignBitHidingHDQ(piQCoef.buf, piCoef.buf, deltaU, cctx, maxLog2TrDynamicRange);
      }
    }
  } //if RDOQ
  //return;
}