HEVC帧间预测之一——TComDataCU::getInterMergeCandidates函数分析

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从今天开始,正式转入到帧间预测方向。由于帧间预测涉及到的方面广且复杂,所以我的理解出现错误的情况可能会更多,请大家以辩证的眼光来看待我的帖子,有问题欢迎大家批评指正。

 

大家都知道xCompressCU是实际进行预测编码的函数,故很容易就能锁定帧间预测的一个大致范围,在研究了帧内预测的基础上,相信很快就能在该函数中找到与帧间预测相关的函数:xCheckRDCostInter,xCheckRDCostMerge2Nx2N。前者进行除了merge模式以外的所有帧间预测,后者则是针对merge模式的。由于merge模式相对于H.264来说是个新事物,我们考虑先从研究它入手。

 

进入到xCheckRDCostMerge2Nx2N函数后,开头有一个比较重要的函数getInterMergeCandidates,它的功能是创建一个merge list,在该模式中是个很重要的函数,故我们先讨论它。下面按照惯例,给出我对这个函数的注释:

 

Void TComDataCU::getInterMergeCandidates( UInt uiAbsPartIdx, UInt uiPUIdx, TComMvField* pcMvFieldNeighbours, UChar* puhInterDirNeighbours, Int& numValidMergeCand, Int mrgCandIdx ){  UInt uiAbsPartAddr = m_uiAbsIdxInLCU + uiAbsPartIdx; //!< 当前CU的ZScan地址  UInt uiIdx = 1;  Bool abCandIsInter[ MRG_MAX_NUM_CANDS ];  for( UInt ui = 0; ui < getSlice()->getMaxNumMergeCand(); ++ui ) //!< m_maxNumMergeCand = 5  {    abCandIsInter[ui] = false;  }  numValidMergeCand = getSlice()->getMaxNumMergeCand(); //!< 5  // compute the location of the current PU  Int xP, yP, nPSW, nPSH;  this->getPartPosition(uiPUIdx, xP, yP, nPSW, nPSH); //!< 获得当前PU的地址和大小  Int iCount = 0; //!< 统计Merge candidate的个数  UInt uiPartIdxLT, uiPartIdxRT, uiPartIdxLB;  PartSize cCurPS = getPartitionSize( uiAbsPartIdx ); //!< CU的分割模式  deriveLeftRightTopIdxGeneral( uiAbsPartIdx, uiPUIdx, uiPartIdxLT, uiPartIdxRT ); //!< 左上部,右上部  deriveLeftBottomIdxGeneral  ( uiAbsPartIdx, uiPUIdx, uiPartIdxLB ); //!< 左下部  //left  UInt uiLeftPartIdx = 0;  TComDataCU* pcCULeft = 0;  pcCULeft = getPULeft( uiLeftPartIdx, uiPartIdxLB, true, false );#if MERGE_CLEANUP_AND_K0197 //!< 在有多个PU在一个CU中的时候,去除第二个PU对A1和B1的依赖性  Bool isAvailableA1 = pcCULeft &&  pcCULeft->isDiffMER(xP -1, yP+nPSH-1, xP, yP) && //!< 当前PU和它的相邻PU不在同一个ME区域  !( uiPUIdx == 1 && (cCurPS == SIZE_Nx2N || cCurPS == SIZE_nLx2N || cCurPS == SIZE_nRx2N) ) &&  !pcCULeft->isIntra( uiLeftPartIdx ) ;  if ( isAvailableA1 )#else  if (pcCULeft)  {    if (!pcCULeft->isDiffMER(xP -1, yP+nPSH-1, xP, yP))    {      pcCULeft = NULL;    }  }  PartSize partSize = getPartitionSize( uiAbsPartIdx );  if (!(uiPUIdx == 1 && (partSize == SIZE_Nx2N || partSize == SIZE_nLx2N || partSize == SIZE_nRx2N)))  {  if ( pcCULeft && !pcCULeft->isIntra( uiLeftPartIdx ) )#endif  {    abCandIsInter[iCount] = true;    // get Inter Dir    puhInterDirNeighbours[iCount] = pcCULeft->getInterDir( uiLeftPartIdx ); //!< inter dir分L0,L1,Bi    // get Mv from Left,将pcCULeft的MV存放到pcMvFieldNeighbours中    pcCULeft->getMvField( pcCULeft, uiLeftPartIdx, REF_PIC_LIST_0, pcMvFieldNeighbours[iCount<<1] );    if ( getSlice()->isInterB() )    {      pcCULeft->getMvField( pcCULeft, uiLeftPartIdx, REF_PIC_LIST_1, pcMvFieldNeighbours[(iCount<<1)+1] );    }    if ( mrgCandIdx == iCount )    {      return;    }    iCount ++;  }#if !MERGE_CLEANUP_AND_K0197  }#endif    // early termination  if (iCount == getSlice()->getMaxNumMergeCand())   {    return;  }  // above  UInt uiAbovePartIdx = 0;  TComDataCU* pcCUAbove = 0;#if LINEBUF_CLEANUP  pcCUAbove = getPUAbove( uiAbovePartIdx, uiPartIdxRT, true, false );#else  pcCUAbove = getPUAbove( uiAbovePartIdx, uiPartIdxRT, true, false, true );#endif#if MERGE_CLEANUP_AND_K0197 //!<   Bool isAvailableB1 = pcCUAbove &&  pcCUAbove->isDiffMER(xP+nPSW-1, yP-1, xP, yP) &&  !( uiPUIdx == 1 && (cCurPS == SIZE_2NxN || cCurPS == SIZE_2NxnU || cCurPS == SIZE_2NxnD) ) &&  !pcCUAbove->isIntra( uiAbovePartIdx );  if ( isAvailableB1 && (!isAvailableA1 || !pcCULeft->hasEqualMotion( uiLeftPartIdx, pcCUAbove, uiAbovePartIdx ) ) )#else//!< 如果A1可用,则检查A1和B1的MV是否相同,否则不需要检查  if (pcCUAbove)  {    if (!pcCUAbove->isDiffMER(xP+nPSW-1, yP-1, xP, yP))    {      pcCUAbove = NULL;    }  }  if ( pcCUAbove && !pcCUAbove->isIntra( uiAbovePartIdx )     && !(uiPUIdx == 1 && (cCurPS == SIZE_2NxN || cCurPS == SIZE_2NxnU || cCurPS == SIZE_2NxnD))    && ( !pcCULeft || pcCULeft->isIntra( uiLeftPartIdx ) || !pcCULeft->hasEqualMotion( uiLeftPartIdx, pcCUAbove, uiAbovePartIdx ) ) )#endif  {    abCandIsInter[iCount] = true;    // get Inter Dir    puhInterDirNeighbours[iCount] = pcCUAbove->getInterDir( uiAbovePartIdx );    // get Mv from Above    pcCUAbove->getMvField( pcCUAbove, uiAbovePartIdx, REF_PIC_LIST_0, pcMvFieldNeighbours[iCount<<1] );    if ( getSlice()->isInterB() )    {      pcCUAbove->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  UInt uiAboveRightPartIdx = 0;  TComDataCU* pcCUAboveRight = 0;#if LINEBUF_CLEANUP  pcCUAboveRight = getPUAboveRight( uiAboveRightPartIdx, uiPartIdxRT, true, false );#else  pcCUAboveRight = getPUAboveRight( uiAboveRightPartIdx, uiPartIdxRT, true, false, true );#endif#if MERGE_CLEANUP_AND_K0197  Bool isAvailableB0 = pcCUAboveRight &&  pcCUAboveRight->isDiffMER(xP+nPSW, yP-1, xP, yP) &&  !pcCUAboveRight->isIntra( uiAboveRightPartIdx );  if ( isAvailableB0 && ( !isAvailableB1 || !pcCUAbove->hasEqualMotion( uiAbovePartIdx, pcCUAboveRight, uiAboveRightPartIdx ) ) )#else//!< 如果B1可用,则检查B1和B0的MV是否相同,否则不需要检查  if (pcCUAboveRight)  {    if (!pcCUAboveRight->isDiffMER(xP+nPSW, yP-1, xP, yP))    {      pcCUAboveRight = NULL;    }  }  if ( pcCUAboveRight && !pcCUAboveRight->isIntra( uiAboveRightPartIdx ) && ( !pcCUAbove || pcCUAbove->isIntra( uiAbovePartIdx ) || !pcCUAbove->hasEqualMotion( uiAbovePartIdx, pcCUAboveRight, uiAboveRightPartIdx ) ) )#endif  {    abCandIsInter[iCount] = true;    // get Inter Dir    puhInterDirNeighbours[iCount] = pcCUAboveRight->getInterDir( uiAboveRightPartIdx );    // get Mv from AboveRight    pcCUAboveRight->getMvField( pcCUAboveRight, uiAboveRightPartIdx, REF_PIC_LIST_0, pcMvFieldNeighbours[iCount<<1] );    if ( getSlice()->isInterB() )    {      pcCUAboveRight->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  UInt uiLeftBottomPartIdx = 0;  TComDataCU* pcCULeftBottom = 0;  pcCULeftBottom = this->getPUBelowLeft( uiLeftBottomPartIdx, uiPartIdxLB, true, false );#if MERGE_CLEANUP_AND_K0197  Bool isAvailableA0 = pcCULeftBottom &&  pcCULeftBottom->isDiffMER(xP-1, yP+nPSH, xP, yP) &&  !pcCULeftBottom->isIntra( uiLeftBottomPartIdx ) ;  if ( isAvailableA0 && ( !isAvailableA1 || !pcCULeft->hasEqualMotion( uiLeftPartIdx, pcCULeftBottom, uiLeftBottomPartIdx ) ) )#else//!< 如果A1可用,则检查A1和A0的MV是否相同,否则不需要检查  if (pcCULeftBottom)  {    if (!pcCULeftBottom->isDiffMER(xP-1, yP+nPSH, xP, yP))    {      pcCULeftBottom = NULL;    }  }  if ( pcCULeftBottom && !pcCULeftBottom->isIntra( uiLeftBottomPartIdx ) && ( !pcCULeft || pcCULeft->isIntra( uiLeftPartIdx ) || !pcCULeft->hasEqualMotion( uiLeftPartIdx, pcCULeftBottom, uiLeftBottomPartIdx ) ) )#endif  {    abCandIsInter[iCount] = true;    // get Inter Dir    puhInterDirNeighbours[iCount] = pcCULeftBottom->getInterDir( uiLeftBottomPartIdx );    // get Mv from LeftBottom    pcCULeftBottom->getMvField( pcCULeftBottom, uiLeftBottomPartIdx, REF_PIC_LIST_0, pcMvFieldNeighbours[iCount<<1] );    if ( getSlice()->isInterB() )    {      pcCULeftBottom->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   if( iCount < 4 )  {    UInt uiAboveLeftPartIdx = 0;    TComDataCU* pcCUAboveLeft = 0;#if LINEBUF_CLEANUP    pcCUAboveLeft = getPUAboveLeft( uiAboveLeftPartIdx, uiAbsPartAddr, true, false );#else    pcCUAboveLeft = getPUAboveLeft( uiAboveLeftPartIdx, uiAbsPartAddr, true, false, true );#endif#if MERGE_CLEANUP_AND_K0197    Bool isAvailableB2 = pcCUAboveLeft &&    pcCUAboveLeft->isDiffMER(xP-1, yP-1, xP, yP) &&    !pcCUAboveLeft->isIntra( uiAboveLeftPartIdx );    if ( isAvailableB2 && ( !isAvailableA1 || !pcCULeft->hasEqualMotion( uiLeftPartIdx, pcCUAboveLeft, uiAboveLeftPartIdx ) )        && ( !isAvailableB1 || !pcCUAbove->hasEqualMotion( uiAbovePartIdx, pcCUAboveLeft, uiAboveLeftPartIdx ) ) )#else//!< 分别将B2与A1、B1的mv进行比较    if (pcCUAboveLeft)    {      if (!pcCUAboveLeft->isDiffMER(xP-1, yP-1, xP, yP))      {        pcCUAboveLeft = NULL;      }    }    if( pcCUAboveLeft && !pcCUAboveLeft->isIntra( uiAboveLeftPartIdx )     && ( !pcCULeft || pcCULeft->isIntra( uiLeftPartIdx ) || !pcCULeft->hasEqualMotion( uiLeftPartIdx, pcCUAboveLeft, uiAboveLeftPartIdx ) )     && ( !pcCUAbove || pcCUAbove->isIntra( uiAbovePartIdx ) || !pcCUAbove->hasEqualMotion( uiAbovePartIdx, pcCUAboveLeft, uiAboveLeftPartIdx ) )     )#endif    {      abCandIsInter[iCount] = true;      // get Inter Dir      puhInterDirNeighbours[iCount] = pcCUAboveLeft->getInterDir( uiAboveLeftPartIdx );      // get Mv from AboveLeft      pcCUAboveLeft->getMvField( pcCUAboveLeft, uiAboveLeftPartIdx, REF_PIC_LIST_0, pcMvFieldNeighbours[iCount<<1] );      if ( getSlice()->isInterB() )      {        pcCUAboveLeft->getMvField( pcCUAboveLeft, uiAboveLeftPartIdx, REF_PIC_LIST_1, pcMvFieldNeighbours[(iCount<<1)+1] );      }      if ( mrgCandIdx == iCount )      {        return;      }      iCount ++;    }  }  // early termination  if (iCount == getSlice()->getMaxNumMergeCand()) //!< 如果可用的merge candidates达到预设的最大值(5),则提前退出  {    return;  }  if ( getSlice()->getEnableTMVPFlag()) //!< default is 1  {    //>> MTK colocated-RightBottom    UInt uiPartIdxRB;    Int uiLCUIdx = getAddr();    deriveRightBottomIdx( uiPUIdx, uiPartIdxRB ); //!< 当前PU的右下部的地址    UInt uiAbsPartIdxTmp = g_auiZscanToRaster[uiPartIdxRB];    UInt uiNumPartInCUWidth = m_pcPic->getNumPartInWidth(); //!< CU以partition为单位的宽度    TComMv cColMv;    Int iRefIdx;    if      ( ( m_pcPic->getCU(m_uiCUAddr)->getCUPelX() + g_auiRasterToPelX[uiAbsPartIdxTmp] + m_pcPic->getMinCUWidth() ) >= m_pcSlice->getSPS()->getPicWidthInLumaSamples() )  // image boundary check    {      uiLCUIdx = -1;    }//!< 横坐标超出图像边界    else if ( ( m_pcPic->getCU(m_uiCUAddr)->getCUPelY() + g_auiRasterToPelY[uiAbsPartIdxTmp] + m_pcPic->getMinCUHeight() ) >= m_pcSlice->getSPS()->getPicHeightInLumaSamples() )    {      uiLCUIdx = -1;    }//!< 纵坐标超出图像边界    else    {      if ( ( uiAbsPartIdxTmp % uiNumPartInCUWidth < uiNumPartInCUWidth - 1 ) &&           // is not at the last column of LCU         ( uiAbsPartIdxTmp / uiNumPartInCUWidth < m_pcPic->getNumPartInHeight() - 1 ) ) // is not at the last row    of LCU      {//!< 不在LCU的最后一列且不在LCU的最后一行,SIZE_NxN的第1个PU        uiAbsPartAddr = g_auiRasterToZscan[ uiAbsPartIdxTmp + uiNumPartInCUWidth + 1 ]; //!< 下一行+1        uiLCUIdx = getAddr(); //!< 与当前PU属于相同的CU      }      else if ( uiAbsPartIdxTmp % uiNumPartInCUWidth < uiNumPartInCUWidth - 1 )           // is not at the last column of LCU But is last row of LCU      {//!< 不在LCU的最后一列但在LCU的最后一行,SIZE_Nx2N的第1个PU,SIZE_NxN的第3个PU,SIZE_nLx2N的第1个PU,SIZE_nRx2N的第1个PU        uiAbsPartAddr = g_auiRasterToZscan[ (uiAbsPartIdxTmp + uiNumPartInCUWidth + 1) % m_pcPic->getNumPartInCU() ];        uiLCUIdx = -1 ;       }      else if ( uiAbsPartIdxTmp / uiNumPartInCUWidth < m_pcPic->getNumPartInHeight() - 1 ) // is not at the last row of LCU But is last column of LCU      {//!< 不在LCU的最后一行但在LCU的最后一列,SIZE_2NxN的第1个PU,SIZE_NxN的第2个PU,SIZE_2NxnU的第1个PU,SIZE_2NxnD的第1个PU        uiAbsPartAddr = g_auiRasterToZscan[ uiAbsPartIdxTmp + 1 ];        uiLCUIdx = getAddr() + 1;      }      else //is the right bottom corner of LCU,SIZE_2Nx2N                             {        uiAbsPartAddr = 0;        uiLCUIdx = -1 ;       }    }    iRefIdx = 0;    Bool bExistMV = false;    UInt uiPartIdxCenter;    UInt uiCurLCUIdx = getAddr();    xDeriveCenterIdx( uiPUIdx, uiPartIdxCenter ); //!< 根据uiPUIdx计算PU的中心地址uiPartIdxCenter//! 获取colocated CU的mv,并经scaled过的。    bExistMV = uiLCUIdx >= 0 && xGetColMVP( REF_PIC_LIST_0, uiLCUIdx, uiAbsPartAddr, cColMv, iRefIdx );    if( bExistMV == false )    {      bExistMV = xGetColMVP( REF_PIC_LIST_0, uiCurLCUIdx, uiPartIdxCenter,  cColMv, iRefIdx );    }    if( bExistMV )    {      UInt uiArrayAddr = iCount;      abCandIsInter[uiArrayAddr] = true;      pcMvFieldNeighbours[uiArrayAddr << 1].setMvField( cColMv, iRefIdx );      if ( getSlice()->isInterB() )      {               iRefIdx = 0;        bExistMV = uiLCUIdx >= 0 && xGetColMVP( REF_PIC_LIST_1, uiLCUIdx, uiAbsPartAddr, cColMv, iRefIdx);        if( bExistMV == false )        {          bExistMV = xGetColMVP( REF_PIC_LIST_1, uiCurLCUIdx, uiPartIdxCenter,  cColMv, iRefIdx );        }        if( bExistMV )        {          pcMvFieldNeighbours[ ( uiArrayAddr << 1 ) + 1 ].setMvField( cColMv, iRefIdx );          puhInterDirNeighbours[uiArrayAddr] = 3; //!< Bi        }        else        {          puhInterDirNeighbours[uiArrayAddr] = 1; //!< L0        }      }      else      {        puhInterDirNeighbours[uiArrayAddr] = 1; //!< L0      }      if ( mrgCandIdx == iCount )      {        return;      }      iCount++;    }    uiIdx++;  }  // early termination  if (iCount == getSlice()->getMaxNumMergeCand())   {    return;  }  UInt uiArrayAddr = iCount;  UInt uiCutoff = uiArrayAddr;      if ( getSlice()->isInterB())  {//! 参考draft Table 8-6 ---- Specification of l0CandIdx and l1CandIdx    UInt uiPriorityList0[12] = {0 , 1, 0, 2, 1, 2, 0, 3, 1, 3, 2, 3};    UInt uiPriorityList1[12] = {1 , 0, 2, 0, 2, 1, 3, 0, 3, 1, 3, 2};    for (Int idx=0; idx<uiCutoff*(uiCutoff-1) && uiArrayAddr!= getSlice()->getMaxNumMergeCand(); idx++)    {      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;  }  //! 当可用的merge candidates数目仍小于预设值时,将余量均设置为零运动矢量  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;  while (uiArrayAddr < getSlice()->getMaxNumMergeCand())  {    abCandIsInter[uiArrayAddr] = true;    puhInterDirNeighbours[uiArrayAddr] = 1;    pcMvFieldNeighbours[uiArrayAddr << 1].setMvField( TComMv(0, 0), r); //!< 设置为零运动矢量    if ( getSlice()->isInterB() )    {      puhInterDirNeighbours[uiArrayAddr] = 3;      pcMvFieldNeighbours[(uiArrayAddr << 1) + 1].setMvField(TComMv(0, 0), r);    }    uiArrayAddr++;    if ( refcnt == iNumRefIdx - 1 ) //!< 达到参考帧列表的参考帧数    {      r = 0;    }    else    {      ++r;      ++refcnt;    }  }  numValidMergeCand = uiArrayAddr;}


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