-Merge模式

Merge模式定义

Merge模式为当前PU建立一个MV的候选列表（包含5个候选MV及其对应的参考图像）。计算这五个候选MV的率失真代价（RDcost），选取最优的MV。（其中空域最多4个）

Merge模式候选列表的建立

空域列表

列表按照A1→B1→B0→A0（B2是替补）
若PU不是正方形，则需要注意其他的位置，则A1不存在，因为PU1与PU2MV不能一样（否则就直接是2N*2N模式）

时域列表

临近已编码图像中对应位置PU。此时不能直接选择候选块的信息，需要根据与参考图像的位置关系做相应的比例伸缩调整。
下面是merge模式的代码。

Void TComDataCU::getInterMergeCandidates( UInt uiAbsPartIdx, UInt uiPUIdx, TComMvField* pcMvFieldNeighbours, UChar* puhInterDirNeighbours, Int& numValidMergeCand, Int mrgCandIdx ) const
{
  UInt uiAbsPartAddr = m_absZIdxInCtu + uiAbsPartIdx;
  // 候选MV对应的标记
  Bool abCandIsInter[ MRG_MAX_NUM_CANDS ];
  // 先清空列表
  for( UInt ui = 0; ui < getSlice()->getMaxNumMergeCand(); ++ui )
  {
    abCandIsInter[ui] = false;
    pcMvFieldNeighbours[ ( ui << 1 )     ].setRefIdx(NOT_VALID);
    pcMvFieldNeighbours[ ( ui << 1 ) + 1 ].setRefIdx(NOT_VALID);
  }
  // 获取有效的候选数量
  numValidMergeCand = getSlice()->getMaxNumMergeCand();
  // compute the location of the current PU 计算当前PU的位置
  Int xP, yP, nPSW, nPSH;  //xp，yp表示location of the upper-left corner pixel of the current PU
  this->getPartPosition(uiPUIdx, xP, yP, nPSW, nPSH);//  nPSW,nPSH       当前PU的大小

  Int iCount = 0; // 候选模式的数量

  UInt uiPartIdxLT, uiPartIdxRT, uiPartIdxLB;
  PartSize cCurPS = getPartitionSize( uiAbsPartIdx );
  // 转换成索引 
  deriveLeftRightTopIdxGeneral( uiAbsPartIdx, uiPUIdx, uiPartIdxLT, uiPartIdxRT );
  deriveLeftBottomIdxGeneral( uiAbsPartIdx, uiPUIdx, uiPartIdxLB );

  // 开始进行空域MV预测，处理的顺序是 左边——>上边——>右上角——>左下角——>左上角
  //left 左侧
  UInt uiLeftPartIdx = 0;
  const TComDataCU *pcCULeft = getPULeft( uiLeftPartIdx, uiPartIdxLB );

  Bool isAvailableA1 = pcCULeft &&
                       pcCULeft->isDiffMER(xP -1, yP+nPSH-1, xP, yP) &&

                       !( uiPUIdx == 1 && (cCurPS == SIZE_Nx2N || cCurPS == SIZE_nLx2N || cCurPS == SIZE_nRx2N) ) &&
                       pcCULeft->isInter( uiLeftPartIdx ) ;

  if ( isAvailableA1 )
  {
    abCandIsInter[iCount] = true;
    // get Inter Dir
    puhInterDirNeighbours[iCount] = pcCULeft->getInterDir( uiLeftPartIdx );
    // get Mv from Left
    TComDataCU::getMvField( pcCULeft, uiLeftPartIdx, REF_PIC_LIST_0, pcMvFieldNeighbours[iCount<<1] );
    if ( getSlice()->isInterB() )
    {
      TComDataCU::getMvField( pcCULeft, uiLeftPartIdx, REF_PIC_LIST_1, pcMvFieldNeighbours[(iCount<<1)+1] );
    }
    if ( mrgCandIdx == iCount )
    {
      return;
    }
    iCount ++;
  }

  // early termination
  if (iCount == getSlice()->getMaxNumMergeCand())
  {
    return;
  }
  // above  上方
  UInt uiAbovePartIdx = 0;
  const TComDataCU *pcCUAbove = getPUAbove( uiAbovePartIdx, uiPartIdxRT );

  Bool isAvailableB1 = pcCUAbove &&
                       pcCUAbove->isDiffMER(xP+nPSW-1, yP-1, xP, yP) &&
                       !( uiPUIdx == 1 && (cCurPS == SIZE_2NxN || cCurPS == SIZE_2NxnU || cCurPS == SIZE_2NxnD) ) &&
                       pcCUAbove->isInter( uiAbovePartIdx );

  if ( isAvailableB1 && (!isAvailableA1 || !pcCULeft->hasEqualMotion( uiLeftPartIdx, pcCUAbove, uiAbovePartIdx ) ) )
  {
    abCandIsInter[iCount] = true;
    // get Inter Dir
    puhInterDirNeighbours[iCount] = pcCUAbove->getInterDir( uiAbovePartIdx );
    // get Mv from Left
    TComDataCU::getMvField( pcCUAbove, uiAbovePartIdx, REF_PIC_LIST_0, pcMvFieldNeighbours[iCount<<1] );
    if ( getSlice()->isInterB() )
    {
      TComDataCU::getMvField( pcCUAbove, uiAbovePartIdx, REF_PIC_LIST_1, pcMvFieldNeighbours[(iCount<<1)+1] );
    }
    if ( mrgCandIdx == iCount )
    {
      return;
    }
    iCount ++;
  }
  // early termination
  if (iCount == getSlice()->getMaxNumMergeCand())
  {
    return;
  }

  // above right  右上
  UInt uiAboveRightPartIdx = 0;
  const TComDataCU *pcCUAboveRight = getPUAboveRight( uiAboveRightPartIdx, uiPartIdxRT );

  Bool isAvailableB0 = pcCUAboveRight &&
                       pcCUAboveRight->isDiffMER(xP+nPSW, yP-1, xP, yP) &&
                       pcCUAboveRight->isInter( uiAboveRightPartIdx );

  if ( isAvailableB0 && ( !isAvailableB1 || !pcCUAbove->hasEqualMotion( uiAbovePartIdx, pcCUAboveRight, uiAboveRightPartIdx ) ) )
  {
    abCandIsInter[iCount] = true;
    // get Inter Dir
    puhInterDirNeighbours[iCount] = pcCUAboveRight->getInterDir( uiAboveRightPartIdx );
    // get Mv from Left
    TComDataCU::getMvField( pcCUAboveRight, uiAboveRightPartIdx, REF_PIC_LIST_0, pcMvFieldNeighbours[iCount<<1] );
    if ( getSlice()->isInterB() )
    {
      TComDataCU::getMvField( pcCUAboveRight, uiAboveRightPartIdx, REF_PIC_LIST_1, pcMvFieldNeighbours[(iCount<<1)+1] );
    }
    if ( mrgCandIdx == iCount )
    {
      return;
    }
    iCount ++;
  }
  // early termination
  if (iCount == getSlice()->getMaxNumMergeCand())
  {
    return;
  }

  //left bottom  左下
  UInt uiLeftBottomPartIdx = 0;
  const TComDataCU *pcCULeftBottom = this->getPUBelowLeft( uiLeftBottomPartIdx, uiPartIdxLB );

  Bool isAvailableA0 = pcCULeftBottom &&
                       pcCULeftBottom->isDiffMER(xP-1, yP+nPSH, xP, yP) &&
                       pcCULeftBottom->isInter( uiLeftBottomPartIdx ) ;

  if ( isAvailableA0 && ( !isAvailableA1 || !pcCULeft->hasEqualMotion( uiLeftPartIdx, pcCULeftBottom, uiLeftBottomPartIdx ) ) )
  {
    abCandIsInter[iCount] = true;
    // get Inter Dir
    puhInterDirNeighbours[iCount] = pcCULeftBottom->getInterDir( uiLeftBottomPartIdx );
    // get Mv from Left
    TComDataCU::getMvField( pcCULeftBottom, uiLeftBottomPartIdx, REF_PIC_LIST_0, pcMvFieldNeighbours[iCount<<1] );
    if ( getSlice()->isInterB() )
    {
      TComDataCU::getMvField( pcCULeftBottom, uiLeftBottomPartIdx, REF_PIC_LIST_1, pcMvFieldNeighbours[(iCount<<1)+1] );
    }
    if ( mrgCandIdx == iCount )
    {
      return;
    }
    iCount ++;
  }
  // early termination
  if (iCount == getSlice()->getMaxNumMergeCand())
  {
    return;
  }

  // above left  左上
  if( iCount < 4 )
  {
    UInt uiAboveLeftPartIdx = 0;
    const TComDataCU *pcCUAboveLeft = getPUAboveLeft( uiAboveLeftPartIdx, uiAbsPartAddr );

    Bool isAvailableB2 = pcCUAboveLeft &&
                         pcCUAboveLeft->isDiffMER(xP-1, yP-1, xP, yP) &&
                         pcCUAboveLeft->isInter( uiAboveLeftPartIdx );

    if ( isAvailableB2 && ( !isAvailableA1 || !pcCULeft->hasEqualMotion( uiLeftPartIdx, pcCUAboveLeft, uiAboveLeftPartIdx ) )
        && ( !isAvailableB1 || !pcCUAbove->hasEqualMotion( uiAbovePartIdx, pcCUAboveLeft, uiAboveLeftPartIdx ) ) )
    {
      abCandIsInter[iCount] = true;
      // get Inter Dir
      puhInterDirNeighbours[iCount] = pcCUAboveLeft->getInterDir( uiAboveLeftPartIdx );
      // get Mv from Left
      TComDataCU::getMvField( pcCUAboveLeft, uiAboveLeftPartIdx, REF_PIC_LIST_0, pcMvFieldNeighbours[iCount<<1] );
      if ( getSlice()->isInterB() )
      {
        TComDataCU::getMvField( pcCUAboveLeft, uiAboveLeftPartIdx, REF_PIC_LIST_1, pcMvFieldNeighbours[(iCount<<1)+1] );
      }
      if ( mrgCandIdx == iCount )
      {
        return;
      }
      iCount ++;
    }
  }
  // early termination
  if (iCount == getSlice()->getMaxNumMergeCand())
  {
    return;
  }


  // 如果使用了TMVP（就是时域的MVP（MVP是MV预测）），上面的都是空域MV预测
  if ( getSlice()->getEnableTMVPFlag() )
  {
    //>> MTK colocated-RightBottom
    UInt uiPartIdxRB;

    deriveRightBottomIdx( uiPUIdx, uiPartIdxRB );

    UInt uiAbsPartIdxTmp = g_auiZscanToRaster[uiPartIdxRB];
    const UInt numPartInCtuWidth  = m_pcPic->getNumPartInCtuWidth();
    const UInt numPartInCtuHeight = m_pcPic->getNumPartInCtuHeight();

    TComMv cColMv;
    Int iRefIdx;
    Int ctuRsAddr = -1;

    if (   ( ( m_pcPic->getCtu(m_ctuRsAddr)->getCUPelX() + g_auiRasterToPelX[uiAbsPartIdxTmp] + m_pcPic->getMinCUWidth () ) < m_pcSlice->getSPS()->getPicWidthInLumaSamples () )  // image boundary check
        && ( ( m_pcPic->getCtu(m_ctuRsAddr)->getCUPelY() + g_auiRasterToPelY[uiAbsPartIdxTmp] + m_pcPic->getMinCUHeight() ) < m_pcSlice->getSPS()->getPicHeightInLumaSamples() ) )
    {
      if ( ( uiAbsPartIdxTmp % numPartInCtuWidth < numPartInCtuWidth - 1 ) &&           // is not at the last column of CTU
        ( uiAbsPartIdxTmp / numPartInCtuWidth < numPartInCtuHeight - 1 ) )              // is not at the last row    of CTU
      {
        uiAbsPartAddr = g_auiRasterToZscan[ uiAbsPartIdxTmp + numPartInCtuWidth + 1 ];
        ctuRsAddr = getCtuRsAddr();
      }
      else if ( uiAbsPartIdxTmp % numPartInCtuWidth < numPartInCtuWidth - 1 )           // is not at the last column of CTU But is last row of CTU
      {
        uiAbsPartAddr = g_auiRasterToZscan[ (uiAbsPartIdxTmp + numPartInCtuWidth + 1) % m_pcPic->getNumPartitionsInCtu() ];
      }
      else if ( uiAbsPartIdxTmp / numPartInCtuWidth < numPartInCtuHeight - 1 )          // is not at the last row of CTU But is last column of CTU
      {
        uiAbsPartAddr = g_auiRasterToZscan[ uiAbsPartIdxTmp + 1 ];
        ctuRsAddr = getCtuRsAddr() + 1;
      }
      else //is the right bottom corner of CTU
      {
        uiAbsPartAddr = 0;
      }
    }

    iRefIdx = 0;

    Bool bExistMV = false;
    UInt uiPartIdxCenter;
    Int dir = 0;
    UInt uiArrayAddr = iCount;
    xDeriveCenterIdx( uiPUIdx, uiPartIdxCenter );

    // 从参考列表中找到预测的MV（xGetColMVP是个比较重要的函数，它的作用是从参考帧中找打MVP）
    bExistMV = ctuRsAddr >= 0 && xGetColMVP( REF_PIC_LIST_0, ctuRsAddr, uiAbsPartAddr, cColMv, iRefIdx );
    if( bExistMV == false )
    {
      bExistMV = xGetColMVP( REF_PIC_LIST_0, getCtuRsAddr(), uiPartIdxCenter,  cColMv, iRefIdx );
    }
    if( bExistMV )
    {
      dir |= 1;
      pcMvFieldNeighbours[ 2 * uiArrayAddr ].setMvField( cColMv, iRefIdx );
    }
    // 如果是B帧，那么还需要在list中查找
    if ( getSlice()->isInterB() )
    {
      bExistMV = ctuRsAddr >= 0 && xGetColMVP( REF_PIC_LIST_1, ctuRsAddr, uiAbsPartAddr, cColMv, iRefIdx);
      if( bExistMV == false )
      {
        bExistMV = xGetColMVP( REF_PIC_LIST_1, getCtuRsAddr(), uiPartIdxCenter, cColMv, iRefIdx );
      }
      if( bExistMV )
      {
        dir |= 2;
        pcMvFieldNeighbours[ 2 * uiArrayAddr + 1 ].setMvField( cColMv, iRefIdx );
      }
    }

    if (dir != 0)
    {
      puhInterDirNeighbours[uiArrayAddr] = dir;
      abCandIsInter[uiArrayAddr] = true;

      if ( mrgCandIdx == iCount )
      {
        return;
      }
      iCount++;
    }
  }
  // early termination
  if (iCount == getSlice()->getMaxNumMergeCand())
  {
    return;
  }

  UInt uiArrayAddr = iCount;
  UInt uiCutoff = uiArrayAddr;

  // 如果是B帧
  if ( getSlice()->isInterB() )
  {
    static const UInt NUM_PRIORITY_LIST=12;
    static const UInt uiPriorityList0[NUM_PRIORITY_LIST] = {0 , 1, 0, 2, 1, 2, 0, 3, 1, 3, 2, 3};
    static const UInt uiPriorityList1[NUM_PRIORITY_LIST] = {1 , 0, 2, 0, 2, 1, 3, 0, 3, 1, 3, 2};

    for (Int idx=0; idx<uiCutoff*(uiCutoff-1) && uiArrayAddr!= getSlice()->getMaxNumMergeCand(); idx++)
    {
      assert(idx<NUM_PRIORITY_LIST);
      Int i = uiPriorityList0[idx];
      Int j = uiPriorityList1[idx];
      if (abCandIsInter[i] && abCandIsInter[j]&& (puhInterDirNeighbours[i]&0x1)&&(puhInterDirNeighbours[j]&0x2))
      {
        abCandIsInter[uiArrayAddr] = true;
        puhInterDirNeighbours[uiArrayAddr] = 3;

        // get Mv from cand[i] and cand[j]
        pcMvFieldNeighbours[uiArrayAddr << 1].setMvField(pcMvFieldNeighbours[i<<1].getMv(), pcMvFieldNeighbours[i<<1].getRefIdx());
        pcMvFieldNeighbours[( uiArrayAddr << 1 ) + 1].setMvField(pcMvFieldNeighbours[(j<<1)+1].getMv(), pcMvFieldNeighbours[(j<<1)+1].getRefIdx());

        Int iRefPOCL0 = m_pcSlice->getRefPOC( REF_PIC_LIST_0, pcMvFieldNeighbours[(uiArrayAddr<<1)].getRefIdx() );
        Int iRefPOCL1 = m_pcSlice->getRefPOC( REF_PIC_LIST_1, pcMvFieldNeighbours[(uiArrayAddr<<1)+1].getRefIdx() );
        if (iRefPOCL0 == iRefPOCL1 && pcMvFieldNeighbours[(uiArrayAddr<<1)].getMv() == pcMvFieldNeighbours[(uiArrayAddr<<1)+1].getMv())
        {
          abCandIsInter[uiArrayAddr] = false;
        }
        else
        {
          uiArrayAddr++;
        }
      }
    }
  }
  // early termination
  if (uiArrayAddr == getSlice()->getMaxNumMergeCand())
  {
    return;
  }

  Int iNumRefIdx = (getSlice()->isInterB()) ? min(m_pcSlice->getNumRefIdx(REF_PIC_LIST_0), m_pcSlice->getNumRefIdx(REF_PIC_LIST_1)) : m_pcSlice->getNumRefIdx(REF_PIC_LIST_0);

  Int r = 0;
  Int refcnt = 0;

  // 如果有必要，那么填充0向量
  while (uiArrayAddr < getSlice()->getMaxNumMergeCand())
  {
    abCandIsInter[uiArrayAddr] = true;
    puhInterDirNeighbours[uiArrayAddr] = 1;
    pcMvFieldNeighbours[uiArrayAddr << 1].setMvField( TComMv(0, 0), r);

    if ( getSlice()->isInterB() )
    {
      puhInterDirNeighbours[uiArrayAddr] = 3;
      pcMvFieldNeighbours[(uiArrayAddr << 1) + 1].setMvField(TComMv(0, 0), r);
    }
    uiArrayAddr++;

    if ( refcnt == iNumRefIdx - 1 )
    {
      r = 0;
    }
    else
    {
      ++r;
      ++refcnt;
    }
  }
  numValidMergeCand = uiArrayAddr;
}

/** Check whether the current PU and a spatial neighboring PU are in a same ME region.
 * \param xN, yN   location of the upper-left corner pixel of a neighboring PU
 * \param xP, yP   location of the upper-left corner pixel of the current PU
 */
Bool TComDataCU::isDiffMER(Int xN, Int yN, Int xP, Int yP) const
{

  UInt plevel = this->getSlice()->getPPS()->getLog2ParallelMergeLevelMinus2() + 2;
  if ((xN>>plevel)!= (xP>>plevel))
  {
    return true;
  }
  if ((yN>>plevel)!= (yP>>plevel))
  {
    return true;
  }
  return false;
}