其實HM的運動估計這部分與H.264相比基本沒有變化，如果看過JMVC運動估計的程式碼，會發現xTZSearch的結構幾乎就是一樣的。所以，嚴格來講，這部分的東西沒有什麼太多新鮮的東西，相信以前研究過TZSearch的人看這部分程式碼會很輕鬆。先看運動估計的主調函式：

//!< 運動估計
Void TEncSearch::xMotionEstimation( TComDataCU* pcCU, TComYuv* pcYuvOrg, Int iPartIdx, RefPicList eRefPicList, TComMv* pcMvPred, Int iRefIdxPred, TComMv& rcMv, UInt& ruiBits, UInt& ruiCost, Bool bBi  )
{
  UInt          uiPartAddr;
  Int           iRoiWidth;
  Int           iRoiHeight;
  
  TComMv        cMvHalf, cMvQter;
  TComMv        cMvSrchRngLT;
  TComMv        cMvSrchRngRB;
  
  TComYuv*      pcYuv = pcYuvOrg;
  m_iSearchRange = m_aaiAdaptSR[eRefPicList][iRefIdxPred]; //!< 根據參考幀列表型別、參考幀序號自適應設定搜尋範圍
  
  Int           iSrchRng      = ( bBi ? m_bipredSearchRange : m_iSearchRange ); //!< 根據是否是雙向預測設定搜尋範圍
  TComPattern*  pcPatternKey  = pcCU->getPattern        (); //!< 用於獲取neighbor的資訊
  
  Double        fWeight       = 1.0;
  
  pcCU->getPartIndexAndSize( iPartIdx, uiPartAddr, iRoiWidth, iRoiHeight ); //!< 獲取PU的地址，寬度和高度
  
  if ( bBi )
  {
    TComYuv*  pcYuvOther = &m_acYuvPred[1-(Int)eRefPicList];
    pcYuv                = &m_cYuvPredTemp;
    
    pcYuvOrg->copyPartToPartYuv( pcYuv, uiPartAddr, iRoiWidth, iRoiHeight );
    
    pcYuv->removeHighFreq( pcYuvOther, uiPartAddr, iRoiWidth, iRoiHeight );
    
    fWeight = 0.5;
  }
  
  //  Search key pattern initialization
  pcPatternKey->initPattern( pcYuv->getLumaAddr( uiPartAddr ),
                            pcYuv->getCbAddr  ( uiPartAddr ),
                            pcYuv->getCrAddr  ( uiPartAddr ),
                            iRoiWidth,
                            iRoiHeight,
                            pcYuv->getStride(),
                            0, 0, 0, 0 ); //!< 設定待搜尋的PU的相關引數，首地址，寬度，高度，跨度等
  //!< 獲取參考影象首地址和跨度
  Pel*        piRefY      = pcCU->getSlice()->getRefPic( eRefPicList, iRefIdxPred )->getPicYuvRec()->getLumaAddr( pcCU->getAddr(), pcCU->getZorderIdxInCU() + uiPartAddr );
  Int         iRefStride  = pcCU->getSlice()->getRefPic( eRefPicList, iRefIdxPred )->getPicYuvRec()->getStride();
  
  TComMv      cMvPred = *pcMvPred;
  //!< 設定運動估計的搜尋範圍，LeftTop & RightBottom
  if ( bBi )  xSetSearchRange   ( pcCU, rcMv   , iSrchRng, cMvSrchRngLT, cMvSrchRngRB );
  else        xSetSearchRange   ( pcCU, cMvPred, iSrchRng, cMvSrchRngLT, cMvSrchRngRB );
  
  m_pcRdCost->getMotionCost ( 1, 0 );
  
  m_pcRdCost->setPredictor  ( *pcMvPred ); //!< m_mvPredictor = *pcMvPred
  m_pcRdCost->setCostScale  ( 2 );

  setWpScalingDistParam( pcCU, iRefIdxPred, eRefPicList ); //!< 設定跟weighted prediction相關的引數
  //  Do integer search
  if ( !m_iFastSearch || bBi ) //!< m_iFastSearch is true
  {
    xPatternSearch      ( pcPatternKey, piRefY, iRefStride, &cMvSrchRngLT, &cMvSrchRngRB, rcMv, ruiCost );
  }
  else //!< Fast Search
  {
    rcMv = *pcMvPred;
    xPatternSearchFast  ( pcCU, pcPatternKey, piRefY, iRefStride, &cMvSrchRngLT, &cMvSrchRngRB, rcMv, ruiCost );
  }
  
  m_pcRdCost->getMotionCost( 1, 0 );
  m_pcRdCost->setCostScale ( 1 );
  
  {//!< 分畫素搜尋
    xPatternSearchFracDIF( pcCU, pcPatternKey, piRefY, iRefStride, &rcMv, cMvHalf, cMvQter, ruiCost
                          ,bBi
                          );
  }
  
  
  
  m_pcRdCost->setCostScale( 0 );
  rcMv <<= 2;						//!< 整畫素
  rcMv += (cMvHalf <<= 1);	//!< 1/2 畫素
  rcMv +=  cMvQter;				//!< 1/4 畫素
  //!< 故rcMv最終以1/4畫素為單位
  UInt uiMvBits = m_pcRdCost->getBits( rcMv.getHor(), rcMv.getVer() );
  
  ruiBits      += uiMvBits;
  ruiCost       = (UInt)( floor( fWeight * ( (Double)ruiCost - (Double)m_pcRdCost->getCost( uiMvBits ) ) ) + (Double)m_pcRdCost->getCost( ruiBits ) );
}
 

基本思想就是用TZSearch演算法先進行整畫素搜尋，確定一個區域性的最佳值，然後以這個最佳點為中心再進行精度更高的分畫素搜尋。

接下來我們先考慮整畫素搜尋的情況，進入到xPatternSearchFast中去：

Void TEncSearch::xPatternSearchFast( TComDataCU* pcCU, TComPattern* pcPatternKey, Pel* piRefY, Int iRefStride, TComMv* pcMvSrchRngLT, TComMv* pcMvSrchRngRB, TComMv& rcMv, UInt& ruiSAD )
{//!< 獲取相鄰PU: A, B, C的運動向量，作為預測運動向量
  pcCU->getMvPredLeft       ( m_acMvPredictors[0] );
  pcCU->getMvPredAbove      ( m_acMvPredictors[1] );
  pcCU->getMvPredAboveRight ( m_acMvPredictors[2] );
  
  switch ( m_iFastSearch )
  {
    case 1:
      xTZSearch( pcCU, pcPatternKey, piRefY, iRefStride, pcMvSrchRngLT, pcMvSrchRngRB, rcMv, ruiSAD );
      break;
      
    default:
      break;
  }
}
 

我們可以看到，這個函式很短，先是獲得預測的運動向量，接著呼叫xTZSearch進行搜尋，xTZSearch這個函式相對比較長，裡面呼叫了很多子函式，因此，一口氣講完這個函式不容易，改為一步步分析各個子函式，再合起來分析xTZSearch的整體功能。