【HEVC学习与研究】46、HEVC参考代码中SAO的实现

1、HM10 encoder关于SAO的初始化操作

在编码开始之前，编码器将进行与SAO有关的一些初始化设置。如在TAppEncTop::encode()函数中调用TAppEncTop::xInitLibCfg()进行与config相关的设置：

  m_cTEncTop.setLFCrossSliceBoundaryFlag( m_bLFCrossSliceBoundaryFlag );//parseCfg时设置，指定loop filter是否能跨越slice边界，默认为false
  m_cTEncTop.setUseSAO ( m_bUseSAO );//parseCfg时设置，指定SAO功能是否开启，由cfg文件指定
  m_cTEncTop.setMaxNumOffsetsPerPic (m_maxNumOffsetsPerPic);//每一个像素最大允许的偏移量，默认为2048

  m_cTEncTop.setSaoLcuBoundary (m_saoLcuBoundary);//是否使用非deblocked像素做SAO参数估计
  m_cTEncTop.setSaoLcuBasedOptimization (m_saoLcuBasedOptimization);//选择基于picture还是CTU的估计，默认选择CTU

  if (m_bUseSAO)
  {
    m_cEncSAO.setSaoLcuBoundary(getSaoLcuBoundary());
    m_cEncSAO.setSaoLcuBasedOptimization(getSaoLcuBasedOptimization());
    m_cEncSAO.setMaxNumOffsetsPerPic(getMaxNumOffsetsPerPic());
    m_cEncSAO.create( getSourceWidth(), getSourceHeight(), g_uiMaxCUWidth, g_uiMaxCUHeight );
    m_cEncSAO.createEncBuffer();
  }

Void TEncGOP::init ( TEncTop* pcTEncTop )
{//......
  //--Adaptive Loop filter
  m_pcSAO                = pcTEncTop->getSAO();
  //......
}

在TEncGOP::compressGOP函数中调用SAOProcess实现：

Void TEncSampleAdaptiveOffset::SAOProcess(SAOParam *pcSaoParam, Double dLambda)
#endif
{
  m_dLambdaLuma    = dLambdaLuma;
  m_dLambdaChroma  = dLambdaChroma;

  if(m_bUseNIF)
  {
    m_pcPic->getPicYuvRec()->copyToPic(m_pcYuvTmp);
  }

  m_uiSaoBitIncreaseY = max(g_bitDepthY - 10, 0);
  m_uiSaoBitIncreaseC = max(g_bitDepthC - 10, 0);
  m_iOffsetThY = 1 << min(g_bitDepthY - 5, 5);
  m_iOffsetThC = 1 << min(g_bitDepthC - 5, 5);
  resetSAOParam(pcSaoParam);
  if( !m_saoLcuBasedOptimization || !m_saoLcuBoundary )
  {
    resetStats();
  }
  Double dCostFinal = 0;
  if ( m_saoLcuBasedOptimization)
  {
    rdoSaoUnitAll(pcSaoParam, dLambdaLuma, dLambdaChroma, depth);
  }
  else
  {
    pcSaoParam->bSaoFlag[0] = 1;
    pcSaoParam->bSaoFlag[1] = 0;
    dCostFinal = 0;
    Double lambdaRdo =  dLambdaLuma;
    resetStats();
    getSaoStats(pcSaoParam->psSaoPart[0], 0);
    runQuadTreeDecision(pcSaoParam->psSaoPart[0], 0, dCostFinal, m_uiMaxSplitLevel, lambdaRdo, 0);
    pcSaoParam->bSaoFlag[0] = dCostFinal < 0 ? 1:0;
    if(pcSaoParam->bSaoFlag[0])
    {
      convertQT2SaoUnit(pcSaoParam, 0, 0);
      assignSaoUnitSyntax(pcSaoParam->saoLcuParam[0],  pcSaoParam->psSaoPart[0], pcSaoParam->oneUnitFlag[0], 0);
    }
  }
  if (pcSaoParam->bSaoFlag[0])
  {
    processSaoUnitAll( pcSaoParam->saoLcuParam[0], pcSaoParam->oneUnitFlag[0], 0);
  }
  if (pcSaoParam->bSaoFlag[1])
  {
    processSaoUnitAll( pcSaoParam->saoLcuParam[1], pcSaoParam->oneUnitFlag[1], 1);
    processSaoUnitAll( pcSaoParam->saoLcuParam[2], pcSaoParam->oneUnitFlag[2], 2);
  }
}