HEVC新技术（一）：基于MVC的AMVP技术

基于MVC（Motion Vector Competition）的AMVP（Advanced Motion Vector Prediction）

技术是HEVC采用的新技术之一。

所谓AMVP，就是通过空域相邻PU以及时域相邻PU的运动矢量信息构造出一个预测运动矢

量候选列表，通过遍历运动矢量候选列表，选择最佳的预测运动矢量。

在HEVC参考软件HM14.0中对应的代码如下：

// AMVP(Advanced Motion Vector Prediction)

#if ZERO_MVD_EST
Void TEncSearch::xEstimateMvPredAMVP( TComDataCU* pcCU, TComYuv* pcOrgYuv, UInt uiPartIdx, RefPicList eRefPicList, Int iRefIdx, TComMv& rcMvPred, Bool bFilled, UInt* puiDistBiP, UInt* puiDist  )
#else
Void TEncSearch::xEstimateMvPredAMVP( TComDataCU* pcCU, TComYuv* pcOrgYuv, UInt uiPartIdx, RefPicList eRefPicList, Int iRefIdx, TComMv& rcMvPred, Bool bFilled, UInt* puiDistBiP )
#endif
{
  AMVPInfo* pcAMVPInfo = pcCU->getCUMvField(eRefPicList)->getAMVPInfo();

  TComMv  cBestMv;
  Int     iBestIdx = 0;
  TComMv  cZeroMv;
  TComMv  cMvPred;
  UInt    uiBestCost = MAX_INT;
  UInt    uiPartAddr = 0;
  Int     iRoiWidth, iRoiHeight;
  Int     i;

  pcCU->getPartIndexAndSize( uiPartIdx, uiPartAddr, iRoiWidth, iRoiHeight );
  // Fill the MV Candidates
  if (!bFilled)
  {
    pcCU->fillMvpCand( uiPartIdx, uiPartAddr, eRefPicList, iRefIdx, pcAMVPInfo );
  }

  // initialize Mvp index & Mvp
  iBestIdx = 0;
  cBestMv  = pcAMVPInfo->m_acMvCand[0];
#if !ZERO_MVD_EST
  if (pcAMVPInfo->iN <= 1)
  {
    rcMvPred = cBestMv;

    pcCU->setMVPIdxSubParts( iBestIdx, eRefPicList, uiPartAddr, uiPartIdx, pcCU->getDepth(uiPartAddr));
    pcCU->setMVPNumSubParts( pcAMVPInfo->iN, eRefPicList, uiPartAddr, uiPartIdx, pcCU->getDepth(uiPartAddr));

    if(pcCU->getSlice()->getMvdL1ZeroFlag() && eRefPicList==REF_PIC_LIST_1)
    {
#if ZERO_MVD_EST
      (*puiDistBiP) = xGetTemplateCost( pcCU, uiPartIdx, uiPartAddr, pcOrgYuv, &m_cYuvPredTemp, rcMvPred, 0, AMVP_MAX_NUM_CANDS, eRefPicList, iRefIdx, iRoiWidth, iRoiHeight, uiDist );
#else
      (*puiDistBiP) = xGetTemplateCost( pcCU, uiPartIdx, uiPartAddr, pcOrgYuv, &m_cYuvPredTemp, rcMvPred, 0, AMVP_MAX_NUM_CANDS, eRefPicList, iRefIdx, iRoiWidth, iRoiHeight);
#endif
    }
    return;
  }
#endif
  if (bFilled)
  {
    assert(pcCU->getMVPIdx(eRefPicList,uiPartAddr) >= 0);
    rcMvPred = pcAMVPInfo->m_acMvCand[pcCU->getMVPIdx(eRefPicList,uiPartAddr)];
    return;
  }

  m_cYuvPredTemp.clear();
#if ZERO_MVD_EST
  UInt uiDist;
#endif
  //-- Check Minimum Cost.
  for ( i = 0 ; i < pcAMVPInfo->iN; i++)
  {
    UInt uiTmpCost;
#if ZERO_MVD_EST
    uiTmpCost = xGetTemplateCost( pcCU, uiPartIdx, uiPartAddr, pcOrgYuv, &m_cYuvPredTemp, pcAMVPInfo->m_acMvCand[i], i, AMVP_MAX_NUM_CANDS, eRefPicList, iRefIdx, iRoiWidth, iRoiHeight, uiDist );
#else
    uiTmpCost = xGetTemplateCost( pcCU, uiPartIdx, uiPartAddr, pcOrgYuv, &m_cYuvPredTemp, pcAMVPInfo->m_acMvCand[i], i, AMVP_MAX_NUM_CANDS, eRefPicList, iRefIdx, iRoiWidth, iRoiHeight);
#endif
    if ( uiBestCost > uiTmpCost )
    {
      uiBestCost = uiTmpCost;
      cBestMv   = pcAMVPInfo->m_acMvCand[i];
      iBestIdx  = i;
      (*puiDistBiP) = uiTmpCost;
#if ZERO_MVD_EST
      (*puiDist) = uiDist;
#endif
    }
  }

  m_cYuvPredTemp.clear();

  // Setting Best MVP
  rcMvPred = cBestMv;
  pcCU->setMVPIdxSubParts( iBestIdx, eRefPicList, uiPartAddr, uiPartIdx, pcCU->getDepth(uiPartAddr));
  pcCU->setMVPNumSubParts( pcAMVPInfo->iN, eRefPicList, uiPartAddr, uiPartIdx, pcCU->getDepth(uiPartAddr));
  return;
}

利用AMVP技术可以充分挖掘时域相关性和空域相关性，提高编码效率。