HEVC帧内预测参考像素检测获取和滤波

作者：66

（转载请注明出处）

还是参考HEVC_CJL的博客，理论都清楚，跟着他的进度看代码，感谢前辈的分享，他的代码里没有强滤波过程，在此我稍加补充。

原文链接：http://blog.csdn.net/hevc_cjl/article/category/1283611

分析initAdiPattern函数，其中调用了之前的fillReferenceSample函数。

initAdiPattern实现的功能如下，1.先按4x4块从左下到右上检测每个块是否可用。2.调用fillReferenceSample填充参考样点。3.参考样点的滤波，分了常规滤波和强滤波。另外，HEVC_CJL博客中最后uiWidth，uiHeigth标识错误了，经几次确认后，应该是uiWidth=2*uiCuWidth，uiHeith=2*uiCuHeigth。

具体过程见代码注释，肯定也有表述不完备的地方，请不吝赐教：

Void TComPattern::initAdiPattern( TComDataCU* pcCU, UInt uiZorderIdxInPart, UInt uiPartDepth, Int* piAdiBuf, Int iOrgBufStride, Int iOrgBufHeight, Bool& bAbove, Bool& bLeft, Bool bLMmode )
{Pel*  piRoiOrigin;//当前cu首地址Int*  piAdiTemp;UInt  uiCuWidth   = pcCU->getWidth(0) >> uiPartDepth;//cu宽度，uiPartDepth为四叉树深度UInt  uiCuHeight  = pcCU->getHeight(0)>> uiPartDepth;//cu高度UInt  uiCuWidth2  = uiCuWidth<<1;UInt  uiCuHeight2 = uiCuHeight<<1;UInt  uiWidth;//cu宽度UInt  uiHeight;//cu高度Int   iPicStride = pcCU->getPic()->getStride();//每次步进的距离Int   iUnitSize = 0;//4*4块Int   iNumUnitsInCu = 0;Int   iTotalUnits = 0;//总共包含的4*4块数量Bool  bNeighborFlags[4 * MAX_NUM_SPU_W + 1];//标记参考像素是否可用，4*16+1Int   iNumIntraNeighbor = 0;//可用的相邻块数UInt uiPartIdxLT, uiPartIdxRT, uiPartIdxLB;//获取当前PU左上、右上、左下以4x4为单位的ZorderpcCU->deriveLeftRightTopIdxAdi( uiPartIdxLT, uiPartIdxRT, uiZorderIdxInPart, uiPartDepth );pcCU->deriveLeftBottomIdxAdi  ( uiPartIdxLB,              uiZorderIdxInPart, uiPartDepth );iUnitSize      = g_uiMaxCUWidth >> g_uiMaxCUDepth;//4x4iNumUnitsInCu  = uiCuWidth / iUnitSize;iTotalUnits    = (iNumUnitsInCu << 2) + 1;//Top + RightTop\+ Left + LeftBottom + LeftTop = iNumUnitsInCu + iNumUnitsInCu + iNumUnitsInCu + iNumUnitsInCu + 1//统计可用总数量，扫描顺序从左下到左上，再到右上bNeighborFlags[iNumUnitsInCu*2] = isAboveLeftAvailable( pcCU, uiPartIdxLT );//统计左上iNumIntraNeighbor  += (Int)(bNeighborFlags[iNumUnitsInCu*2]);iNumIntraNeighbor  += isAboveAvailable     ( pcCU, uiPartIdxLT, uiPartIdxRT, bNeighborFlags+(iNumUnitsInCu*2)+1 );//上，这个函数的\四个参数解释分别为当前pu编号，开始参考像素块号，结束块号，标志数组当前的位置指针iNumIntraNeighbor  += isAboveRightAvailable( pcCU, uiPartIdxLT, uiPartIdxRT, bNeighborFlags+(iNumUnitsInCu*3)+1 );//右上iNumIntraNeighbor  += isLeftAvailable      ( pcCU, uiPartIdxLT, uiPartIdxLB, bNeighborFlags+(iNumUnitsInCu*2)-1 );//左iNumIntraNeighbor  += isBelowLeftAvailable ( pcCU, uiPartIdxLT, uiPartIdxLB, bNeighborFlags+ iNumUnitsInCu   -1 );//左下bAbove = true;bLeft  = true;//uiWidth、uiHeight与uiCuWidth,uiCuHeight不一样uiWidth=uiCuWidth2+1;//lefttop+above+rightaboveuiHeight=uiCuHeight2+1;//lefttop+left+leftbelow//超出buf的长 if (((uiWidth<<2)>iOrgBufStride)||((uiHeight<<2)>iOrgBufHeight)){return;}piRoiOrigin = pcCU->getPic()->getPicYuvRec()->getLumaAddr(pcCU->getAddr(), pcCU->getZorderIdxInCU()+uiZorderIdxInPart);piAdiTemp   = piAdiBuf;fillReferenceSamples (g_bitDepthY, piRoiOrigin, piAdiTemp, bNeighborFlags, iNumIntraNeighbor, iUnitSize, iNumUnitsInCu, iTotalUnits, uiCuWidth, uiCuHeight, uiWidth, uiHeight, iPicStride, bLMmode);Int   i;// generate filtered intra prediction samples参考像素滤波Int iBufSize = uiCuHeight2 + uiCuWidth2 + 1;  // left and left above border + above and above right border + top left corner = length of 3. filter bufferUInt uiWH = uiWidth * uiHeight;               // number of elements in one bufferbuf的大小//piFilteredBuf1最终参考像素放置的bufInt* piFilteredBuf1 = piAdiBuf + uiWH;        // 1. filter bufferInt* piFilteredBuf2 = piFilteredBuf1 + uiWH;  // 2. filter buffer//piFilterBuf中进行滤波计算Int* piFilterBuf = piFilteredBuf2 + uiWH;     // buffer for 2. filtering (sequential)//此处存放经滤波后的值Int* piFilterBufN = piFilterBuf + iBufSize;   // buffer for 1. filtering (sequential)//draft8.4.2.3Filtering process of neighbouring sampleInt l = 0;//左下到右上// left border from bottom to topfor (i = 0; i < uiCuHeight2; i++)//将处理后的参考样点值放到piFilterBuf中{piFilterBuf[l++] = piAdiTemp[uiWidth * (uiCuHeight2 - i)];}// top left cornerpiFilterBuf[l++] = piAdiTemp[0];// above border from left to rightfor (i=0; i < uiCuWidth2; i++){piFilterBuf[l++] = piAdiTemp[1 + i];}//判断是否进行强滤波if (pcCU->getSlice()->getSPS()->getUseStrongIntraSmoothing()){Int blkSize = 32;//强滤波块大小限定值，需要大于32的块Int bottomLeft = piFilterBuf[0];//左下角一个像素Int topLeft = piFilterBuf[uiCuHeight2];//左上角像素Int topRight = piFilterBuf[iBufSize-1];//右上角像素Int threshold = 1 << (g_bitDepthY - 5);//强滤波判断阈值//左下+左上-2*左中间<阈值Bool bilinearLeft = abs(bottomLeft+topLeft-2*piFilterBuf[uiCuHeight]) < threshold;//左上+右上-2*上中间<阈值Bool bilinearAbove  = abs(topLeft+topRight-2*piFilterBuf[uiCuHeight2+uiCuHeight]) < threshold;//强滤波if (uiCuWidth>=blkSize && (bilinearLeft && bilinearAbove)){Int shift = g_aucConvertToBit[uiCuWidth] + 3;  // log2(uiCuHeight2)=log2(64)=6piFilterBufN[0] = piFilterBuf[0];//复制左下piFilterBufN[uiCuHeight2] = piFilterBuf[uiCuHeight2];//左上piFilterBufN[iBufSize - 1] = piFilterBuf[iBufSize - 1];//右上//滤波的权值与据本边界两顶点的距离有关for (i = 1; i < uiCuHeight2; i++)//垂直方向滤波{//uiCuHeitht2 = (64-纵坐标)*左上+纵坐标*右上+32piFilterBufN[i] = ((uiCuHeight2-i)*bottomLeft + i*topLeft + uiCuHeight) >> shift;}for (i = 1; i < uiCuWidth2; i++)//水平方向滤波{//同上piFilterBufN[uiCuHeight2 + i] = ((uiCuWidth2-i)*topLeft + i*topRight + uiCuWidth) >> shift;}}else {// 1. filtering with [1 2 1]，常规滤波piFilterBufN[0] = piFilterBuf[0];//左下最后一个的参考像素点piFilterBufN[iBufSize - 1] = piFilterBuf[iBufSize - 1];//右上最后一个for (i = 1; i < iBufSize - 1; i++){piFilterBufN[i] = (piFilterBuf[i - 1] + 2 * piFilterBuf[i]+piFilterBuf[i + 1] + 2) >> 2;}}}else {//常规滤波，同上，注意代码结构，并非进行两次。// 1. filtering with [1 2 1]piFilterBufN[0] = piFilterBuf[0];piFilterBufN[iBufSize - 1] = piFilterBuf[iBufSize - 1];for (i = 1; i < iBufSize - 1; i++){piFilterBufN[i] = (piFilterBuf[i - 1] + 2 * piFilterBuf[i]+piFilterBuf[i + 1] + 2) >> 2;}}//滤波后的参考像素复制到piFilteredBuf1中// fill 1. filter buffer with filtered valuesl=0;for (i = 0; i < uiCuHeight2; i++)//垂直方向，从下到上{piFilteredBuf1[uiWidth * (uiCuHeight2 - i)] = piFilterBufN[l++];}piFilteredBuf1[0] = piFilterBufN[l++];//左上顶点for (i = 0; i < uiCuWidth2; i++)//水平方向{piFilteredBuf1[1 + i] = piFilterBufN[l++];}
}

其实这个代码有些细节很有意思，应该设计到可移植性和以后的更新维护，有时间了研究一下。

（转载请务必注明出处）

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