今天主要介紹幀內預測一個很重要的函式initAdiPattern，它的主要功能有三個，（1）檢測當前PU的相鄰樣點包括左上、上、右上、左、左下鄰域樣點值的可用性，或者說檢查這些點是否存在；（2）參考樣點的替換過程，主要實現的是JCTVC-J1003即draft 8.4.4.2.2的內容，主要由函式fillReferenceSamples來完成，這個在之前的文章已經討論過了；（3）相鄰樣點即參考樣點的平滑濾波，主要實現draft 8.4.4.2.3的內容。話不多說，下面給出initAdiPattern的實現和我個人的一些註釋，供大家參考。

Void TComPattern::initAdiPattern( TComDataCU* pcCU, UInt uiZorderIdxInPart, UInt uiPartDepth, Int* piAdiBuf, Int iOrgBufStride, Int iOrgBufHeight, Bool& bAbove, Bool& bLeft, Bool bLMmode )
{//! bLMmode is usually false 
  Pel*  piRoiOrigin;
  Int*  piAdiTemp;
  UInt  uiCuWidth   = pcCU->getWidth(0) >> uiPartDepth; //!< CU的寬度
  UInt  uiCuHeight  = pcCU->getHeight(0)>> uiPartDepth; //!< CU的高度
  UInt  uiCuWidth2  = uiCuWidth<<1;
  UInt  uiCuHeight2 = uiCuHeight<<1;
  UInt  uiWidth;
  UInt  uiHeight;
  Int   iPicStride = pcCU->getPic()->getStride();
  Int   iUnitSize = 0;
  Int   iNumUnitsInCu = 0;
  Int   iTotalUnits = 0;
  Bool  bNeighborFlags[4 * MAX_NUM_SPU_W + 1];  //!< 用於存放4個方向上的相鄰樣點值的可用性, 4 x 32 + 1
  Int   iNumIntraNeighbor = 0; //!< 給可用鄰塊進行計數
  
  UInt uiPartIdxLT, uiPartIdxRT, uiPartIdxLB;

  //! 獲取當前PU左上角LT，右上角RT以及左下角LB 以4x4塊為單位的Zorder
  pcCU->deriveLeftRightTopIdxAdi( uiPartIdxLT, uiPartIdxRT, uiZorderIdxInPart, uiPartDepth );
  pcCU->deriveLeftBottomIdxAdi  ( uiPartIdxLB,              uiZorderIdxInPart, uiPartDepth );
  
  iUnitSize      = g_uiMaxCUWidth >> g_uiMaxCUDepth;
  iNumUnitsInCu  = uiCuWidth / iUnitSize;
  iTotalUnits    = (iNumUnitsInCu << 2) + 1; // Top + RightTop + Left + LeftBottom + LeftTop = iNumUnitsInCu + iNumUnitsInCu + iNumUnitsInCu + iNumUnitsInCu + 1
  //! 掃描順序是從左下到左上，再從左上到右上
  bNeighborFlags[iNumUnitsInCu*2] = isAboveLeftAvailable( pcCU, uiPartIdxLT );
  iNumIntraNeighbor  += (Int)(bNeighborFlags[iNumUnitsInCu*2]);
  iNumIntraNeighbor  += isAboveAvailable     ( pcCU, uiPartIdxLT, uiPartIdxRT, bNeighborFlags+(iNumUnitsInCu*2)+1 );
  iNumIntraNeighbor  += isAboveRightAvailable( pcCU, uiPartIdxLT, uiPartIdxRT, bNeighborFlags+(iNumUnitsInCu*3)+1 );
  iNumIntraNeighbor  += isLeftAvailable      ( pcCU, uiPartIdxLT, uiPartIdxLB, bNeighborFlags+(iNumUnitsInCu*2)-1 );
  iNumIntraNeighbor  += isBelowLeftAvailable ( pcCU, uiPartIdxLT, uiPartIdxLB, bNeighborFlags+ iNumUnitsInCu   -1 );
  
  bAbove = true;
  bLeft  = true;

  uiWidth=uiCuWidth2+1;
  uiHeight=uiCuHeight2+1;
  
  if (((uiWidth<<2)>iOrgBufStride)||((uiHeight<<2)>iOrgBufHeight))
  {
    return;
  }
  //! piRoiOrigin指向當前PU左上角
  piRoiOrigin = pcCU->getPic()->getPicYuvRec()->getLumaAddr(pcCU->getAddr(), pcCU->getZorderIdxInCU()+uiZorderIdxInPart);
  piAdiTemp   = piAdiBuf;

  fillReferenceSamples ( pcCU, piRoiOrigin, piAdiTemp, bNeighborFlags, iNumIntraNeighbor, iUnitSize, iNumUnitsInCu, iTotalUnits, uiCuWidth, uiCuHeight, uiWidth, uiHeight, iPicStride, bLMmode);
  
  Int   i;
  // generate filtered intra prediction samples
  Int iBufSize = uiCuHeight2 + uiCuWidth2 + 1;  // left and left above border + above and above right border + top left corner = length of 3. filter buffer

  UInt uiWH = uiWidth * uiHeight;               // number of elements in one buffer

  //! 下面所進行的工作主要是對參考樣點進行3抽頭的濾波。piAdiBuf指向濾波前的參考樣點的首地址，在濾波前，先將所有參考樣點
  //! 拷貝到piFilterBuf指向的區域，經濾波後的樣點值儲存在piFilterBufN指向的區域，最終將濾波後的樣點值拷貝到piFilterBuf1
  //! 值得一提的是，最終的結果是，piAdiBuf指向的區域是未經濾波的樣點值，而piFilterBuf1指向的區域是經過濾波的樣點值，
  //! 兩者的地址相差uiWH = uiWidth * uiHeight = (uiCuWidth2 + 1) * (uiCuHeight2 + 1)，這就解釋了在進行真正的幀內預測時，
  //! 在需要濾波時，指向piAdiBuf的指標需要加上uiWH的偏移量
  Int* piFilteredBuf1 = piAdiBuf + uiWH;        // 1. filter buffer
  Int* piFilteredBuf2 = piFilteredBuf1 + uiWH;  // 2. filter buffer
  Int* piFilterBuf = piFilteredBuf2 + uiWH;     // buffer for 2. filtering (sequential)
  Int* piFilterBufN = piFilterBuf + iBufSize;   // buffer for 1. filtering (sequential) //!<存放的是參考樣點經3抽頭濾波後的值

  // draft 8.4.4.2.3 Filtering process of neighbouring samples
  Int l = 0;
  // left border from bottom to top
  for (i = 0; i < uiCuHeight2; i++)
  {
    piFilterBuf[l++] = piAdiTemp[uiWidth * (uiCuHeight2 - i)]; //!< 左邊界，儲存順序為從下往上
  }
  // top left corner
  piFilterBuf[l++] = piAdiTemp[0];  //!< 左上邊界
  // above border from left to right
  for (i=0; i < uiCuWidth2; i++)
  {
    piFilterBuf[l++] = piAdiTemp[1 + i];  //!<上邊界，儲存順序為從左往右
  }

  // 1. filtering with [1 2 1]
  piFilterBufN[0] = piFilterBuf[0]; //!< 第1個點直接儲存，不濾波
  piFilterBufN[iBufSize - 1] = piFilterBuf[iBufSize - 1]; //!< 最後一個點也直接儲存，不濾波
  for (i = 1; i < iBufSize - 1; i++) //!< 對中間樣點值進行3抽頭[1 2 1] / 4 的平滑濾波
  {
    piFilterBufN[i] = (piFilterBuf[i - 1] + 2 * piFilterBuf[i]+piFilterBuf[i + 1] + 2) >> 2;
  }

  // fill 1. filter buffer with filtered values
  l=0;
  for (i = 0; i < uiCuHeight2; i++)
  {
    piFilteredBuf1[uiWidth * (uiCuHeight2 - i)] = piFilterBufN[l++];  // left border from bottom to top //!< 左邊界
  }
  piFilteredBuf1[0] = piFilterBufN[l++]; //!< 左上邊界
  for (i = 0; i < uiCuWidth2; i++)
  {
    piFilteredBuf1[1 + i] = piFilterBufN[l++]; // above border from left to right //!< 上邊界
  }
}
 

最後附上圖，以幫助大家更好地理解程式碼，我就不對圖多作解釋了，相信大家對著程式碼能比較容易看明白的。

 （注，上圖中，uiWidth和uiHeight實際上對應的是程式碼中的uiCUWidth和uiCUHeight，因畫圖的時候發生了遺漏，特此說明）

（轉載請註明出處。）