【HEVC学习与研究】31、HM编码器的基本结构

来源：互联网发布：java socket经常断开编辑：程序博客网时间：2024/06/05 10:17

通过解码器代码的研究，已经对HEVC的编解码技术有了一个初步的认识。现在我们就对照着编码器的代码进一步理解HEVC视频编码算法的各个技术细节。

编码器在整个HM解决方案中的工程名为TAppEncoder，入口点函数位于encmain.cpp文件中：

int main(int argc, char* argv[]){TAppEncTop  cTAppEncTop;// print informationfprintf( stdout, "\n" );fprintf( stdout, "HM software: Encoder Version [%s]", NV_VERSION );fprintf( stdout, NVM_ONOS );fprintf( stdout, NVM_COMPILEDBY );fprintf( stdout, NVM_BITS );fprintf( stdout, "\n" );// create application encoder classcTAppEncTop.create();// parse configurationtry{if(!cTAppEncTop.parseCfg( argc, argv )){cTAppEncTop.destroy();return 1;}}catch (po::ParseFailure& e){cerr << "Error parsing option \""<< e.arg <<"\" with argument \""<< e.val <<"\"." << endl;return 1;}// starting timedouble dResult;long lBefore = clock();// call encoding functioncTAppEncTop.encode();// ending timedResult = (double)(clock()-lBefore) / CLOCKS_PER_SEC;printf("\n Total Time: %12.3f sec.\n", dResult);// destroy application encoder classcTAppEncTop.destroy();return 0;}

可以很清楚地看到，整个main函数非常简洁清晰，主要可以分为几大部分，分别是输入软件信息、创建编码器类的实例、解析配置文件、获取开始时间、编码数据、计算耗费时间和销毁编码器类的实例几大部分。我们主要关心的编码过程仅通过调用编码器实例的一个方法实现：

// call encoding functioncTAppEncTop.encode();

该函数的实现如下：

Void TAppEncTop::encode(){fstream bitstreamFile(m_pchBitstreamFile, fstream::binary | fstream::out);if (!bitstreamFile){fprintf(stderr, "\nfailed to open bitstream file `%s' for writing\n", m_pchBitstreamFile);exit(EXIT_FAILURE);}TComPicYuv*       pcPicYuvOrg = new TComPicYuv;TComPicYuv*       pcPicYuvRec = NULL;// initialize internal class & member variablesxInitLibCfg();xCreateLib();xInitLib();// main encoder loopInt   iNumEncoded = 0;Bool  bEos = false;list<AccessUnit> outputAccessUnits; ///< list of access units to write out.  is populated by the encoding process// allocate original YUV bufferpcPicYuvOrg->create( m_iSourceWidth, m_iSourceHeight, m_uiMaxCUWidth, m_uiMaxCUHeight, m_uiMaxCUDepth );while ( !bEos ){// get buffersxGetBuffer(pcPicYuvRec);// read input YUV filem_cTVideoIOYuvInputFile.read( pcPicYuvOrg, m_aiPad );// increase number of received framesm_iFrameRcvd++;bEos = (m_iFrameRcvd == m_framesToBeEncoded);Bool flush = 0;// if end of file (which is only detected on a read failure) flush the encoder of any queued picturesif (m_cTVideoIOYuvInputFile.isEof()){flush = true;bEos = true;m_iFrameRcvd--;m_cTEncTop.setFramesToBeEncoded(m_iFrameRcvd);}// call encoding function for one framem_cTEncTop.encode( bEos, flush ? 0 : pcPicYuvOrg, m_cListPicYuvRec, outputAccessUnits, iNumEncoded );// write bistream to file if necessaryif ( iNumEncoded > 0 ){xWriteOutput(bitstreamFile, iNumEncoded, outputAccessUnits);outputAccessUnits.clear();}}m_cTEncTop.printSummary();// delete original YUV bufferpcPicYuvOrg->destroy();delete pcPicYuvOrg;pcPicYuvOrg = NULL;// delete used buffers in encoder classm_cTEncTop.deletePicBuffer();// delete buffers & classesxDeleteBuffer();xDestroyLib();printRateSummary();return;}

该函数中首先调用pcPicYuvOrg->create( m_iSourceWidth, m_iSourceHeight, m_uiMaxCUWidth, m_uiMaxCUHeight, m_uiMaxCUDepth )分配YUV数据缓存，然后再while循环中逐帧读取YUV数据、设置当前以编码的帧数、编码当前帧、写出码流，随后做其他清理工作。核心功能实现在m_cTEncTop.encode( bEos, flush ? 0 : pcPicYuvOrg, m_cListPicYuvRec, outputAccessUnits, iNumEncoded )函数中。在该函数中调用m_cGOPEncoder.compressGOP(m_iPOCLast, m_iNumPicRcvd, m_cListPic, rcListPicYuvRecOut, accessUnitsOut)进行编码一个GOP的操作。这个函数奇长无比，用了接近1500行代码，看来实现了很多很多很多的功能。这个碉堡了的函数究竟做了些啥事儿呢？这个函数中大部分内容就是在为了编码当前slice做准备，以及编码完成之后一些辅助操作。实际编码过程的操作由以下函数m_pcSliceEncoder->compressSlice( pcPic )实现。

这又是一个碉堡了的函数，占了将近400行……代码就不贴了，会死人的……简单看下好了。

首先还是各种编码的配置，包括配置熵编码器、初始化CU编码器等。在完成了一长串的设置之后，在compressCU函数中实现对一个CU的编码：

      m_pcCuEncoder->compressCU( pcCU );

具体的细节，且待下文。

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