HEVC代码追踪（十一。七）:运动估计/补偿之xTZ8PointDiamondSearch

xTZSearch调用了2个最为主要的函数：xTZ8PointDiamondSearch和xTZ2PointSearch，值得一提的是，HM中还提供了另外一个搜索函数xTZ8PointSquareSearch，但由于实际并没有使用这个函数，且它其实跟钻石搜索只是搜索点的选择略有不同，分析起来基本上也是一样的。

__inline Void TEncSearch::xTZ8PointDiamondSearch( TComPattern* pcPatternKey, IntTZSearchStruct& rcStruct, TComMv* pcMvSrchRngLT, TComMv* pcMvSrchRngRB, const Int iStartX, const Int iStartY, const Int iDist )
{
  Int   iSrchRngHorLeft   = pcMvSrchRngLT->getHor();
  Int   iSrchRngHorRight  = pcMvSrchRngRB->getHor();
  Int   iSrchRngVerTop    = pcMvSrchRngLT->getVer();
  Int   iSrchRngVerBottom = pcMvSrchRngRB->getVer();
  
  // 8 point search,                   //   1 2 3
  // search around the start point     //   4 0 5
  // with the required  distance       //   6 7 8
  assert ( iDist != 0 );
  const Int iTop        = iStartY - iDist;//!< 2
  const Int iBottom     = iStartY + iDist;//!< 7
  const Int iLeft       = iStartX - iDist;//!< 4
  const Int iRight      = iStartX + iDist;//!< 5
  rcStruct.uiBestRound += 1;//!< 每次调用xTZSearchHelp，一旦发现当前搜索点的sad小于存放的最佳值，则将uiBestRound清零  
  
  if ( iDist == 1 ) // iDist == 1
  {//!< 搜索步长等于1时，只搜索2,4,5,7这四个位置，这也就是在后面最佳步长为1时，仍然要进行2点钻石搜索的原因  
    if ( iTop >= iSrchRngVerTop ) // check top
    {
      xTZSearchHelp( pcPatternKey, rcStruct, iStartX, iTop, 2, iDist );
    }
    if ( iLeft >= iSrchRngHorLeft ) // check middle left
    {
      xTZSearchHelp( pcPatternKey, rcStruct, iLeft, iStartY, 4, iDist );
    }
    if ( iRight <= iSrchRngHorRight ) // check middle right
    {
      xTZSearchHelp( pcPatternKey, rcStruct, iRight, iStartY, 5, iDist );
    }
    if ( iBottom <= iSrchRngVerBottom ) // check bottom
    {
      xTZSearchHelp( pcPatternKey, rcStruct, iStartX, iBottom, 7, iDist );
    }
  }
  else // if (iDist != 1)
  {
    if ( iDist <= 8 )
    {
      const Int iTop_2      = iStartY - (iDist>>1);
      const Int iBottom_2   = iStartY + (iDist>>1);
      const Int iLeft_2     = iStartX - (iDist>>1);
      const Int iRight_2    = iStartX + (iDist>>1);
      
      if (  iTop >= iSrchRngVerTop && iLeft >= iSrchRngHorLeft &&
          iRight <= iSrchRngHorRight && iBottom <= iSrchRngVerBottom ) // check border，保证在搜索范围内  
      {
        xTZSearchHelp( pcPatternKey, rcStruct, iStartX,  iTop,      2, iDist    );
        xTZSearchHelp( pcPatternKey, rcStruct, iLeft_2,  iTop_2,    1, iDist>>1 );
        xTZSearchHelp( pcPatternKey, rcStruct, iRight_2, iTop_2,    3, iDist>>1 );
        xTZSearchHelp( pcPatternKey, rcStruct, iLeft,    iStartY,   4, iDist    );
        xTZSearchHelp( pcPatternKey, rcStruct, iRight,   iStartY,   5, iDist    );
        xTZSearchHelp( pcPatternKey, rcStruct, iLeft_2,  iBottom_2, 6, iDist>>1 );
        xTZSearchHelp( pcPatternKey, rcStruct, iRight_2, iBottom_2, 8, iDist>>1 );
        xTZSearchHelp( pcPatternKey, rcStruct, iStartX,  iBottom,   7, iDist    );
      }
      else // check border，有部分越界，在确保不越界的情况下搜索对应点
      {
        if ( iTop >= iSrchRngVerTop ) // check top
        {
          xTZSearchHelp( pcPatternKey, rcStruct, iStartX, iTop, 2, iDist );
        }
        if ( iTop_2 >= iSrchRngVerTop ) // check half top
        {
          if ( iLeft_2 >= iSrchRngHorLeft ) // check half left
          {
            xTZSearchHelp( pcPatternKey, rcStruct, iLeft_2, iTop_2, 1, (iDist>>1) );
          }
          if ( iRight_2 <= iSrchRngHorRight ) // check half right
          {
            xTZSearchHelp( pcPatternKey, rcStruct, iRight_2, iTop_2, 3, (iDist>>1) );
          }
        } // check half top
        if ( iLeft >= iSrchRngHorLeft ) // check left
        {
          xTZSearchHelp( pcPatternKey, rcStruct, iLeft, iStartY, 4, iDist );
        }
        if ( iRight <= iSrchRngHorRight ) // check right
        {
          xTZSearchHelp( pcPatternKey, rcStruct, iRight, iStartY, 5, iDist );
        }
        if ( iBottom_2 <= iSrchRngVerBottom ) // check half bottom
        {
          if ( iLeft_2 >= iSrchRngHorLeft ) // check half left
          {
            xTZSearchHelp( pcPatternKey, rcStruct, iLeft_2, iBottom_2, 6, (iDist>>1) );
          }
          if ( iRight_2 <= iSrchRngHorRight ) // check half right
          {
            xTZSearchHelp( pcPatternKey, rcStruct, iRight_2, iBottom_2, 8, (iDist>>1) );
          }
        } // check half bottom
        if ( iBottom <= iSrchRngVerBottom ) // check bottom
        {
          xTZSearchHelp( pcPatternKey, rcStruct, iStartX, iBottom, 7, iDist );
        }
      } // check border
    }
    else // iDist > 8，搜索步长大于8以后，ucPointNr统一设置为0
    {
      if ( iTop >= iSrchRngVerTop && iLeft >= iSrchRngHorLeft &&
          iRight <= iSrchRngHorRight && iBottom <= iSrchRngVerBottom ) // check border，在搜索范围内  
      {
        xTZSearchHelp( pcPatternKey, rcStruct, iStartX, iTop,    0, iDist );//!< 2
        xTZSearchHelp( pcPatternKey, rcStruct, iLeft,   iStartY, 0, iDist );//!< 4
        xTZSearchHelp( pcPatternKey, rcStruct, iRight,  iStartY, 0, iDist );//!< 5
        xTZSearchHelp( pcPatternKey, rcStruct, iStartX, iBottom, 0, iDist );//!< 7
        for ( Int index = 1; index < 4; index++ )//!< 不妨假设此时iDist = 16，搜索的点可以以(iStartX, iStartY)为原点进行描点，不难得出钻石扫描的pattern
        {
          Int iPosYT = iTop    + ((iDist>>2) * index);//!< iTop + 4 (8, 12)
          Int iPosYB = iBottom - ((iDist>>2) * index);//!< iBottom - 4 (8, 12)  
          Int iPosXL = iStartX - ((iDist>>2) * index);//!< iStartX - 4 (8, 12)
          Int iPosXR = iStartX + ((iDist>>2) * index); //!< iStartX + 4 (8, 12) 
          xTZSearchHelp( pcPatternKey, rcStruct, iPosXL, iPosYT, 0, iDist );
          xTZSearchHelp( pcPatternKey, rcStruct, iPosXR, iPosYT, 0, iDist );
          xTZSearchHelp( pcPatternKey, rcStruct, iPosXL, iPosYB, 0, iDist );
          xTZSearchHelp( pcPatternKey, rcStruct, iPosXR, iPosYB, 0, iDist );
        }
      }
      else // check border，有部分越界，在确保不越界的地方进行搜索
      {
        if ( iTop >= iSrchRngVerTop ) // check top
        {
          xTZSearchHelp( pcPatternKey, rcStruct, iStartX, iTop, 0, iDist );
        }
        if ( iLeft >= iSrchRngHorLeft ) // check left
        {
          xTZSearchHelp( pcPatternKey, rcStruct, iLeft, iStartY, 0, iDist );
        }
        if ( iRight <= iSrchRngHorRight ) // check right
        {
          xTZSearchHelp( pcPatternKey, rcStruct, iRight, iStartY, 0, iDist );
        }
        if ( iBottom <= iSrchRngVerBottom ) // check bottom
        {
          xTZSearchHelp( pcPatternKey, rcStruct, iStartX, iBottom, 0, iDist );
        }
        for ( Int index = 1; index < 4; index++ )
        {
          Int iPosYT = iTop    + ((iDist>>2) * index);
          Int iPosYB = iBottom - ((iDist>>2) * index);
          Int iPosXL = iStartX - ((iDist>>2) * index);
          Int iPosXR = iStartX + ((iDist>>2) * index);
          
          if ( iPosYT >= iSrchRngVerTop ) // check top
          {
            if ( iPosXL >= iSrchRngHorLeft ) // check left
            {
              xTZSearchHelp( pcPatternKey, rcStruct, iPosXL, iPosYT, 0, iDist );
            }
            if ( iPosXR <= iSrchRngHorRight ) // check right
            {
              xTZSearchHelp( pcPatternKey, rcStruct, iPosXR, iPosYT, 0, iDist );
            }
          } // check top
          if ( iPosYB <= iSrchRngVerBottom ) // check bottom
          {
            if ( iPosXL >= iSrchRngHorLeft ) // check left
            {
              xTZSearchHelp( pcPatternKey, rcStruct, iPosXL, iPosYB, 0, iDist );
            }
            if ( iPosXR <= iSrchRngHorRight ) // check right
            {
              xTZSearchHelp( pcPatternKey, rcStruct, iPosXR, iPosYB, 0, iDist );
            }
          } // check bottom
        } // for ...
      } // check border
    } // iDist <= 8
  } // iDist == 1
}