CABACWriter.cpp

/* The copyright in this software is being made available under the BSD
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/** \file     CABACWriter.cpp
 *  \brief    Writer for low level syntax
 */

#include "CommonLib/Contexts.h"
#include "CABACWriter.h"

#include "EncLib.h"

#include "CommonLib/UnitTools.h"
#include "CommonLib/dtrace_buffer.h"

#include <map>
#include <algorithm>
#include <limits>


//! \ingroup EncoderLib
//! \{

void CABACWriter::initCtxModels( const Slice& slice )
{
  int       qp                = slice.getSliceQp();
  SliceType sliceType         = slice.getSliceType();
  SliceType encCABACTableIdx  = slice.getEncCABACTableIdx();
  if( !slice.isIntra() && (encCABACTableIdx==B_SLICE || encCABACTableIdx==P_SLICE) && slice.getPPS()->getCabacInitPresentFlag() )
  {
    sliceType = encCABACTableIdx;
  }
  m_BinEncoder.reset( qp, (int)sliceType );
}



template <class BinProbModel>
SliceType xGetCtxInitId( const Slice& slice, const BinEncIf& binEncoder, Ctx& ctxTest )
{
  const CtxStore<BinProbModel>& ctxStoreTest = static_cast<const CtxStore<BinProbModel>&>( ctxTest );
  const CtxStore<BinProbModel>& ctxStoreRef  = static_cast<const CtxStore<BinProbModel>&>( binEncoder.getCtx() );
  int qp = slice.getSliceQp();
  if( !slice.isIntra() )
  {
    SliceType aSliceTypeChoices[] = { B_SLICE, P_SLICE };
    uint64_t  bestCost            = std::numeric_limits<uint64_t>::max();
    SliceType bestSliceType       = aSliceTypeChoices[0];
    for (uint32_t idx=0; idx<2; idx++)
    {
      uint64_t  curCost           = 0;
      SliceType curSliceType      = aSliceTypeChoices[idx];
      ctxTest.init( qp, (int)curSliceType );
      for( int k = 0; k < Ctx::NumberOfContexts; k++ )
      {
        if( binEncoder.getNumBins(k) > 0 )
        {
          curCost += uint64_t( binEncoder.getNumBins(k) ) * ctxStoreRef[k].estFracExcessBits( ctxStoreTest[k] );
        }
      }
      if (curCost < bestCost)
      {
        bestSliceType = curSliceType;
        bestCost      = curCost;
      }
    }
    return bestSliceType;
  }
  else
  {
    return I_SLICE;
  }
}


SliceType CABACWriter::getCtxInitId( const Slice& slice )
{
  switch( m_TestCtx.getBPMType() )
  {
  case BPM_Std:   return  xGetCtxInitId<BinProbModel_Std>   ( slice, m_BinEncoder, m_TestCtx );
  default:        return  NUMBER_OF_SLICE_TYPES;
  }
}



unsigned estBits( BinEncIf& binEnc, const std::vector<bool>& bins, const Ctx& ctx, const int ctxId, const uint8_t winSize )
{
  binEnc.initCtxAndWinSize( ctxId, ctx, winSize );
  binEnc.start();
  const std::size_t numBins   = bins.size();
  unsigned          startBits = binEnc.getNumWrittenBits();
  for( std::size_t binId = 0; binId < numBins; binId++ )
  {
    unsigned  bin = ( bins[binId] ? 1 : 0 );
    binEnc.encodeBin( bin, ctxId );
  }
  unsigned endBits    = binEnc.getNumWrittenBits();
  unsigned codedBits  = endBits - startBits;
  return   codedBits;
}





//================================================================================
//  clause 7.3.8.1
//--------------------------------------------------------------------------------
//    void  end_of_slice()
//================================================================================

void CABACWriter::end_of_slice()
{
  m_BinEncoder.encodeBinTrm ( 1 );
  m_BinEncoder.finish       ();
}




//================================================================================
//  clause 7.3.8.2
//--------------------------------------------------------------------------------
//    bool  coding_tree_unit( cs, area, qp, ctuRsAddr, skipSao, skipAlf )
//================================================================================

void CABACWriter::coding_tree_unit( CodingStructure& cs, const UnitArea& area, int (&qps)[2], unsigned ctuRsAddr, bool skipSao /* = false */, bool skipAlf /* = false */ )
{
  CUCtx cuCtx( qps[CH_L] );
  QTBTPartitioner partitioner;

  partitioner.initCtu(area, CH_L, *cs.slice);

  if( !skipSao )
  {
    sao( *cs.slice, ctuRsAddr );
  }

  if (!skipAlf)
  {
    for (int compIdx = 0; compIdx < MAX_NUM_COMPONENT; compIdx++)
    {
      codeAlfCtuEnableFlag(cs, ctuRsAddr, compIdx, NULL);
      if (isLuma(ComponentID(compIdx)))
      {
        codeAlfCtuFilterIndex(cs, ctuRsAddr, cs.slice->getTileGroupAlfEnabledFlag(COMPONENT_Y));
      }
      if (isChroma(ComponentID(compIdx)))
      {
        uint8_t* ctbAlfFlag = cs.slice->getTileGroupAlfEnabledFlag((ComponentID)compIdx) ? cs.slice->getPic()->getAlfCtuEnableFlag( compIdx ) : nullptr;
        if( ctbAlfFlag && ctbAlfFlag[ctuRsAddr] )
        {
          codeAlfCtuAlternative( cs, ctuRsAddr, compIdx );
        }
      }
    }
  }

  if ( CS::isDualITree(cs) && cs.pcv->chrFormat != CHROMA_400 && cs.pcv->maxCUWidth > 64 )
  {
    CUCtx chromaCuCtx(qps[CH_C]);
    QTBTPartitioner chromaPartitioner;
    chromaPartitioner.initCtu(area, CH_C, *cs.slice);
    coding_tree(cs, partitioner, cuCtx, &chromaPartitioner, &chromaCuCtx);
    qps[CH_L] = cuCtx.qp;
    qps[CH_C] = chromaCuCtx.qp;
  }
  else
  {
    coding_tree(cs, partitioner, cuCtx);
    qps[CH_L] = cuCtx.qp;
    if( CS::isDualITree( cs ) && cs.pcv->chrFormat != CHROMA_400 )
    {
      CUCtx cuCtxChroma( qps[CH_C] );
      partitioner.initCtu(area, CH_C, *cs.slice);
      coding_tree(cs, partitioner, cuCtxChroma);
      qps[CH_C] = cuCtxChroma.qp;
    }
  }
}





//================================================================================
//  clause 7.3.8.3
//--------------------------------------------------------------------------------
//    void  sao             ( slice, ctuRsAddr )
//    void  sao_block_pars  ( saoPars, bitDepths, sliceEnabled, leftMergeAvail, aboveMergeAvail, onlyEstMergeInfo )
//    void  sao_offset_pars ( ctbPars, compID, sliceEnabled, bitDepth )
//================================================================================

void CABACWriter::sao( const Slice& slice, unsigned ctuRsAddr )
{
  const SPS& sps = *slice.getSPS();
  if( !sps.getSAOEnabledFlag() )
  {
    return;
  }

  CodingStructure&     cs                     = *slice.getPic()->cs;
  const PreCalcValues& pcv                    = *cs.pcv;
  const SAOBlkParam&  sao_ctu_pars            = cs.picture->getSAO()[ctuRsAddr];
  bool                slice_sao_luma_flag     = ( slice.getSaoEnabledFlag( CHANNEL_TYPE_LUMA ) );
  bool                slice_sao_chroma_flag   = ( slice.getSaoEnabledFlag( CHANNEL_TYPE_CHROMA ) && sps.getChromaFormatIdc() != CHROMA_400 );
  if( !slice_sao_luma_flag && !slice_sao_chroma_flag )
  {
    return;
  }

  bool                sliceEnabled[3]         = { slice_sao_luma_flag, slice_sao_chroma_flag, slice_sao_chroma_flag };
  int                 frame_width_in_ctus     = pcv.widthInCtus;
  int                 ry                      = ctuRsAddr      / frame_width_in_ctus;
  int                 rx                      = ctuRsAddr - ry * frame_width_in_ctus;
  const Position      pos                     ( rx * cs.pcv->maxCUWidth, ry * cs.pcv->maxCUHeight );
  const unsigned      curSliceIdx             = slice.getIndependentSliceIdx();
  const unsigned      curTileIdx              = cs.picture->brickMap->getBrickIdxRsMap( pos );
  bool                leftMergeAvail          = cs.getCURestricted( pos.offset( -(int)pcv.maxCUWidth, 0  ), pos, curSliceIdx, curTileIdx, CH_L ) ? true : false;
  bool                aboveMergeAvail         = cs.getCURestricted( pos.offset( 0, -(int)pcv.maxCUHeight ), pos, curSliceIdx, curTileIdx, CH_L ) ? true : false;
  sao_block_pars( sao_ctu_pars, sps.getBitDepths(), sliceEnabled, leftMergeAvail, aboveMergeAvail, false );
}


void CABACWriter::sao_block_pars( const SAOBlkParam& saoPars, const BitDepths& bitDepths, bool* sliceEnabled, bool leftMergeAvail, bool aboveMergeAvail, bool onlyEstMergeInfo )
{
  bool isLeftMerge  = false;
  bool isAboveMerge = false;
  if( leftMergeAvail )
  {
    // sao_merge_left_flag
    isLeftMerge   = ( saoPars[COMPONENT_Y].modeIdc == SAO_MODE_MERGE && saoPars[COMPONENT_Y].typeIdc == SAO_MERGE_LEFT );
    m_BinEncoder.encodeBin( (isLeftMerge), Ctx::SaoMergeFlag() );
  }
  if( aboveMergeAvail && !isLeftMerge )
  {
    // sao_merge_above_flag
    isAboveMerge  = ( saoPars[COMPONENT_Y].modeIdc == SAO_MODE_MERGE && saoPars[COMPONENT_Y].typeIdc == SAO_MERGE_ABOVE );
    m_BinEncoder.encodeBin( (isAboveMerge), Ctx::SaoMergeFlag() );
  }
  if( onlyEstMergeInfo )
  {
    return; //only for RDO
  }
  if( !isLeftMerge && !isAboveMerge )
  {
    // explicit parameters
    for( int compIdx=0; compIdx < MAX_NUM_COMPONENT; compIdx++ )
    {
      sao_offset_pars( saoPars[compIdx], ComponentID(compIdx), sliceEnabled[compIdx], bitDepths.recon[ toChannelType(ComponentID(compIdx)) ] );
    }
  }
}


void CABACWriter::sao_offset_pars( const SAOOffset& ctbPars, ComponentID compID, bool sliceEnabled, int bitDepth )
{
  if( !sliceEnabled )
  {
    CHECK( ctbPars.modeIdc != SAO_MODE_OFF, "Sao must be off, if it is disabled on slice level" );
    return;
  }
  const bool isFirstCompOfChType = ( getFirstComponentOfChannel( toChannelType(compID) ) == compID );

  if( isFirstCompOfChType )
  {
    // sao_type_idx_luma / sao_type_idx_chroma
    if( ctbPars.modeIdc == SAO_MODE_OFF )
    {
      m_BinEncoder.encodeBin  ( 0, Ctx::SaoTypeIdx() );
    }
    else if( ctbPars.typeIdc == SAO_TYPE_BO )
    {
      m_BinEncoder.encodeBin  ( 1, Ctx::SaoTypeIdx() );
      m_BinEncoder.encodeBinEP( 0 );
    }
    else
    {
      CHECK(!( ctbPars.typeIdc < SAO_TYPE_START_BO ), "Unspecified error");
      m_BinEncoder.encodeBin  ( 1, Ctx::SaoTypeIdx() );
      m_BinEncoder.encodeBinEP( 1 );
    }
  }

  if( ctbPars.modeIdc == SAO_MODE_NEW )
  {
    const int maxOffsetQVal = SampleAdaptiveOffset::getMaxOffsetQVal( bitDepth );
    int       numClasses    = ( ctbPars.typeIdc == SAO_TYPE_BO ? 4 : NUM_SAO_EO_CLASSES );
    int       k             = 0;
    int       offset[4];
    for( int i = 0; i < numClasses; i++ )
    {
      if( ctbPars.typeIdc != SAO_TYPE_BO && i == SAO_CLASS_EO_PLAIN )
      {
        continue;
      }
      int classIdx = ( ctbPars.typeIdc == SAO_TYPE_BO ? ( ctbPars.typeAuxInfo + i ) % NUM_SAO_BO_CLASSES : i );
      offset[k++]  = ctbPars.offset[classIdx];
    }

    // sao_offset_abs
    for( int i = 0; i < 4; i++ )
    {
      unsigned absOffset = ( offset[i] < 0 ? -offset[i] : offset[i] );
      unary_max_eqprob( absOffset, maxOffsetQVal );
    }

    // band offset mode
    if( ctbPars.typeIdc == SAO_TYPE_BO )
    {
      // sao_offset_sign
      for( int i = 0; i < 4; i++ )
      {
        if( offset[i] )
        {
          m_BinEncoder.encodeBinEP( (offset[i] < 0) );
        }
      }
      // sao_band_position
      m_BinEncoder.encodeBinsEP( ctbPars.typeAuxInfo, NUM_SAO_BO_CLASSES_LOG2 );
    }
    // edge offset mode
    else
    {
      if( isFirstCompOfChType )
      {
        // sao_eo_class_luma / sao_eo_class_chroma
        CHECK( ctbPars.typeIdc - SAO_TYPE_START_EO < 0, "sao edge offset class is outside valid range" );
        m_BinEncoder.encodeBinsEP( ctbPars.typeIdc - SAO_TYPE_START_EO, NUM_SAO_EO_TYPES_LOG2 );
      }
    }
  }
}



//================================================================================
//  clause 7.3.8.4
//--------------------------------------------------------------------------------
//    void  coding_tree       ( cs, partitioner, cuCtx )
//    void  split_cu_flag     ( split, cs, partitioner )
//    void  split_cu_mode_mt  ( split, cs, partitioner )
//================================================================================

void CABACWriter::coding_tree(const CodingStructure& cs, Partitioner& partitioner, CUCtx& cuCtx, Partitioner* pPartitionerChroma, CUCtx* pCuCtxChroma)
{
  const PPS      &pps         = *cs.pps;
  const UnitArea &currArea    = partitioner.currArea();
  const CodingUnit &cu        = *cs.getCU( currArea.blocks[partitioner.chType], partitioner.chType );

  // Reset delta QP coding flag and ChromaQPAdjustemt coding flag
  //Note: do not reset qg at chroma CU
  if( pps.getUseDQP() && partitioner.currQgEnable() && !isChroma( partitioner.chType ) )
  {
    cuCtx.qgStart    = true;
    cuCtx.isDQPCoded          = false;
  }
  if( cs.slice->getUseChromaQpAdj() && partitioner.currQgChromaEnable() )
  {
    cuCtx.isChromaQpAdjCoded  = false;
  }
  // Reset delta QP coding flag and ChromaQPAdjustemt coding flag
  if (CS::isDualITree(cs) && pPartitionerChroma != nullptr)
  {
    if (pps.getUseDQP() && pPartitionerChroma->currQgEnable())
    {
      pCuCtxChroma->qgStart    = true;
      pCuCtxChroma->isDQPCoded = false;
    }
    if (cs.slice->getUseChromaQpAdj() && pPartitionerChroma->currQgChromaEnable())
    {
      pCuCtxChroma->isChromaQpAdjCoded = false;
    }
  }

  const PartSplit splitMode = CU::getSplitAtDepth( cu, partitioner.currDepth );

  split_cu_mode( splitMode, cs, partitioner );

  CHECK( !partitioner.canSplit( splitMode, cs ), "The chosen split mode is invalid!" );

  if( splitMode != CU_DONT_SPLIT )
  {
      if (CS::isDualITree(cs) && pPartitionerChroma != nullptr && (partitioner.currArea().lwidth() >= 64 || partitioner.currArea().lheight() >= 64))
      {
        partitioner.splitCurrArea(CU_QUAD_SPLIT, cs);
        pPartitionerChroma->splitCurrArea(CU_QUAD_SPLIT, cs);
        bool beContinue = true;
        bool lumaContinue = true;
        bool chromaContinue = true;

        while (beContinue)
        {
          if (partitioner.currArea().lwidth() > 64 || partitioner.currArea().lheight() > 64)
          {
            if (cs.picture->blocks[partitioner.chType].contains(partitioner.currArea().blocks[partitioner.chType].pos()))
            {
              coding_tree(cs, partitioner, cuCtx, pPartitionerChroma, pCuCtxChroma);
            }
            lumaContinue = partitioner.nextPart(cs);
            chromaContinue = pPartitionerChroma->nextPart(cs);
            CHECK(lumaContinue != chromaContinue, "luma chroma partition should be matched");
            beContinue = lumaContinue;
          }
          else
          {
            //dual tree coding under 64x64 block
            if (cs.picture->blocks[partitioner.chType].contains(partitioner.currArea().blocks[partitioner.chType].pos()))
            {
              coding_tree(cs, partitioner, cuCtx);
            }
            lumaContinue = partitioner.nextPart(cs);
            if (cs.picture->blocks[pPartitionerChroma->chType].contains(pPartitionerChroma->currArea().blocks[pPartitionerChroma->chType].pos()))
            {
              coding_tree(cs, *pPartitionerChroma, *pCuCtxChroma);
            }
            chromaContinue = pPartitionerChroma->nextPart(cs);
            CHECK(lumaContinue != chromaContinue, "luma chroma partition should be matched");
            beContinue = lumaContinue;
          }
        }
        partitioner.exitCurrSplit();
        pPartitionerChroma->exitCurrSplit();

      }
      else
      {
        const ModeType modeTypeParent = partitioner.modeType;
        const ModeType modeTypeChild = CU::getModeTypeAtDepth( cu, partitioner.currDepth );
        mode_constraint( splitMode, cs, partitioner, modeTypeChild );
        partitioner.modeType = modeTypeChild;

        bool chromaNotSplit = modeTypeParent == MODE_TYPE_ALL && modeTypeChild == MODE_TYPE_INTRA ? true : false;
        CHECK( chromaNotSplit && partitioner.chType != CHANNEL_TYPE_LUMA, "chType must be luma" );
        if( partitioner.treeType == TREE_D )
        {
          partitioner.treeType = chromaNotSplit ? TREE_L : TREE_D;
        }
      partitioner.splitCurrArea( splitMode, cs );

      do
      {
        if( cs.picture->blocks[partitioner.chType].contains( partitioner.currArea().blocks[partitioner.chType].pos() ) )
        {
          coding_tree( cs, partitioner, cuCtx );
        }
      } while( partitioner.nextPart( cs ) );

      partitioner.exitCurrSplit();
      if( chromaNotSplit )
      {
        CHECK( partitioner.chType != CHANNEL_TYPE_LUMA, "must be luma status" );
        partitioner.chType = CHANNEL_TYPE_CHROMA;
        partitioner.treeType = TREE_C;

        if( cs.picture->blocks[partitioner.chType].contains( partitioner.currArea().blocks[partitioner.chType].pos() ) )
        {
          coding_tree( cs, partitioner, cuCtx );
        }

        //recover
        partitioner.chType = CHANNEL_TYPE_LUMA;
        partitioner.treeType = TREE_D;
      }
      partitioner.modeType = modeTypeParent;
      }
      return;
  }

  // Predict QP on start of quantization group
  if( cuCtx.qgStart )
  {
    cuCtx.qgStart = false;
    cuCtx.qp = CU::predictQP( cu, cuCtx.qp );
  }
  CHECK( cu.treeType != partitioner.treeType, "treeType mismatch" );


  // coding unit
  coding_unit( cu, partitioner, cuCtx );

  if( cu.chType == CHANNEL_TYPE_CHROMA )
  {
    DTRACE_COND( (isEncoding()), g_trace_ctx, D_QP, "[chroma CU]x=%d, y=%d, w=%d, h=%d, qp=%d\n", cu.Cb().x, cu.Cb().y, cu.Cb().width, cu.Cb().height, cu.qp );
  }
  else
  {
  DTRACE_COND( ( isEncoding() ), g_trace_ctx, D_QP, "x=%d, y=%d, w=%d, h=%d, qp=%d\n", cu.Y().x, cu.Y().y, cu.Y().width, cu.Y().height, cu.qp );
  }
  DTRACE_BLOCK_REC_COND( ( !isEncoding() ), cs.picture->getRecoBuf( cu ), cu, cu.predMode );
}

void CABACWriter::mode_constraint( const PartSplit split, const CodingStructure& cs, Partitioner& partitioner, const ModeType modeType )
{
  CHECK( split == CU_DONT_SPLIT, "splitMode shall not be no split" );
  int val = cs.signalModeCons( split, partitioner, partitioner.modeType );
  if( val == LDT_MODE_TYPE_SIGNAL )
  {
    CHECK( modeType == MODE_TYPE_ALL, "shall not be no constraint case" );
    bool flag = modeType == MODE_TYPE_INTRA;
    int ctxIdx = DeriveCtx::CtxModeConsFlag( cs, partitioner );
    m_BinEncoder.encodeBin( flag, Ctx::ModeConsFlag( ctxIdx ) );
    DTRACE( g_trace_ctx, D_SYNTAX, "mode_cons_flag() flag=%d\n", flag );
  }
  else if( val == LDT_MODE_TYPE_INFER )
  {
    assert( modeType == MODE_TYPE_INTRA );
  }
  else
  {
    assert( modeType == partitioner.modeType );
  }
}

void CABACWriter::split_cu_mode( const PartSplit split, const CodingStructure& cs, Partitioner& partitioner )
{
  bool canNo, canQt, canBh, canBv, canTh, canTv;
  partitioner.canSplit( cs, canNo, canQt, canBh, canBv, canTh, canTv );

  bool canSpl[6] = { canNo, canQt, canBh, canBv, canTh, canTv };

  unsigned ctxSplit = 0, ctxQtSplit = 0, ctxBttHV = 0, ctxBttH12 = 0, ctxBttV12;
  DeriveCtx::CtxSplit( cs, partitioner, ctxSplit, ctxQtSplit, ctxBttHV, ctxBttH12, ctxBttV12, canSpl );

  const bool canSplit = canBh || canBv || canTh || canTv || canQt;
  const bool isNo     = split == CU_DONT_SPLIT;

  if( canNo && canSplit )
  {
    m_BinEncoder.encodeBin( !isNo, Ctx::SplitFlag( ctxSplit ) );
  }

  DTRACE( g_trace_ctx, D_SYNTAX, "split_cu_mode() ctx=%d split=%d\n", ctxSplit, !isNo );

  if( isNo )
  {
    return;
  }

  const bool canBtt = canBh || canBv || canTh || canTv;
  const bool isQt   = split == CU_QUAD_SPLIT;

  if( canQt && canBtt )
  {
    m_BinEncoder.encodeBin( isQt, Ctx::SplitQtFlag( ctxQtSplit ) );
  }

  DTRACE( g_trace_ctx, D_SYNTAX, "split_cu_mode() ctx=%d qt=%d\n", ctxQtSplit, isQt );

  if( isQt )
  {
    return;
  }

  const bool canHor = canBh || canTh;
  const bool canVer = canBv || canTv;
  const bool  isVer = split == CU_VERT_SPLIT || split == CU_TRIV_SPLIT;

  if( canVer && canHor )
  {
    m_BinEncoder.encodeBin( isVer, Ctx::SplitHvFlag( ctxBttHV ) );
  }

  const bool can14 = isVer ? canTv : canTh;
  const bool can12 = isVer ? canBv : canBh;
  const bool  is12 = isVer ? ( split == CU_VERT_SPLIT ) : ( split == CU_HORZ_SPLIT );

  if( can12 && can14 )
  {
    m_BinEncoder.encodeBin( is12, Ctx::Split12Flag( isVer ? ctxBttV12 : ctxBttH12 ) );
  }

  DTRACE( g_trace_ctx, D_SYNTAX, "split_cu_mode() ctxHv=%d ctx12=%d mode=%d\n", ctxBttHV, isVer ? ctxBttV12 : ctxBttH12, split );
}

//================================================================================
//  clause 7.3.8.5
//--------------------------------------------------------------------------------
//    void  coding_unit               ( cu, partitioner, cuCtx )
//    void  cu_transquant_bypass_flag ( cu )
//    void  cu_skip_flag              ( cu )
//    void  pred_mode                 ( cu )
//    void  part_mode                 ( cu )
//    void  cu_pred_data              ( pus )
//    void  cu_lic_flag               ( cu )
//    void  intra_luma_pred_modes     ( pus )
//    void  intra_chroma_pred_mode    ( pu )
//    void  cu_residual               ( cu, partitioner, cuCtx )
//    void  rqt_root_cbf              ( cu )
//    void  end_of_ctu                ( cu, cuCtx )
//================================================================================

void CABACWriter::coding_unit( const CodingUnit& cu, Partitioner& partitioner, CUCtx& cuCtx )
{
  DTRACE( g_trace_ctx, D_SYNTAX, "coding_unit() treeType=%d modeType=%d\n", cu.treeType, cu.modeType );
  CodingStructure& cs = *cu.cs;
  // transquant bypass flag
  if( cs.pps->getTransquantBypassEnabledFlag() )
  {
    cu_transquant_bypass_flag( cu );
  }

  // skip flag
  if ((!cs.slice->isIntra() || cs.slice->getSPS()->getIBCFlag()) && cu.Y().valid())
  {
    cu_skip_flag( cu );
  }


  // skip data
  if( cu.skip )
  {
    CHECK( !cu.firstPU->mergeFlag, "Merge flag has to be on!" );
    PredictionUnit&   pu = *cu.firstPU;
    prediction_unit ( pu );
    end_of_ctu      ( cu, cuCtx );
    return;
  }


  // prediction mode and partitioning data
  pred_mode ( cu );
  if (CU::isPLT(cu))
  {
    if (cu.isSepTree())
    {
      if (isLuma(partitioner.chType))
      {
        cu_palette_info(cu, COMPONENT_Y, 1, cuCtx);
      }
      if (cu.chromaFormat != CHROMA_400 && (partitioner.chType == CHANNEL_TYPE_CHROMA))
      {
        cu_palette_info(cu, COMPONENT_Cb, 2, cuCtx);
      }
    }
    else
    {
      cu_palette_info(cu, COMPONENT_Y, 3, cuCtx);
    }
    end_of_ctu(cu, cuCtx);
    return;
  }
  bdpcm_mode( cu, ComponentID( partitioner.chType ) );


  // prediction data ( intra prediction modes / reference indexes + motion vectors )
  cu_pred_data( cu );

  // residual data ( coded block flags + transform coefficient levels )
  cu_residual( cu, partitioner, cuCtx );

  // end of cu
  end_of_ctu( cu, cuCtx );
}


void CABACWriter::cu_transquant_bypass_flag( const CodingUnit& cu )
{
  m_BinEncoder.encodeBin( (cu.transQuantBypass), Ctx::TransquantBypassFlag() );
}


void CABACWriter::cu_skip_flag( const CodingUnit& cu )
{
  unsigned ctxId = DeriveCtx::CtxSkipFlag( cu );

  if ((cu.slice->isIntra() || cu.isConsIntra()) && cu.cs->slice->getSPS()->getIBCFlag())
  {
    if (cu.lwidth() < 128 && cu.lheight() < 128) // disable IBC mode larger than 64x64
    {
    m_BinEncoder.encodeBin((cu.skip), Ctx::SkipFlag(ctxId));
    DTRACE(g_trace_ctx, D_SYNTAX, "cu_skip_flag() ctx=%d skip=%d\n", ctxId, cu.skip ? 1 : 0);
    }
    return;
  }
  if ( !cu.cs->slice->getSPS()->getIBCFlag() && cu.lwidth() == 4 && cu.lheight() == 4 )
  {
    return;
  }
  if( !cu.cs->slice->getSPS()->getIBCFlag() && cu.isConsIntra() )
  {
    return;
  }
  m_BinEncoder.encodeBin( ( cu.skip ), Ctx::SkipFlag( ctxId ) );

  DTRACE( g_trace_ctx, D_SYNTAX, "cu_skip_flag() ctx=%d skip=%d\n", ctxId, cu.skip ? 1 : 0 );
  if (cu.skip && cu.cs->slice->getSPS()->getIBCFlag())
  {
    if (cu.lwidth() < 128 && cu.lheight() < 128 && !cu.isConsInter()) // disable IBC mode larger than 64x64 and disable IBC when only allowing inter mode
    {
      if ( cu.lwidth() == 4 && cu.lheight() == 4 )
      {
        return;
      }
    unsigned ctxidx = DeriveCtx::CtxIBCFlag(cu);
    m_BinEncoder.encodeBin(CU::isIBC(cu) ? 1 : 0, Ctx::IBCFlag(ctxidx));
    DTRACE(g_trace_ctx, D_SYNTAX, "ibc() ctx=%d cu.predMode=%d\n", ctxidx, cu.predMode);
    }
  }
}


void CABACWriter::pred_mode( const CodingUnit& cu )
{
  if (cu.cs->slice->getSPS()->getIBCFlag() && cu.chType != CHANNEL_TYPE_CHROMA)
  {
    if( cu.isConsInter() )
    {
      assert( CU::isInter( cu ) );
      return;
    }

    if ( cu.cs->slice->isIntra() || ( cu.lwidth() == 4 && cu.lheight() == 4 ) || cu.isConsIntra() )
    {
      if (cu.lwidth() < 128 && cu.lheight() < 128) // disable IBC mode larger than 64x64
      {
      unsigned ctxidx = DeriveCtx::CtxIBCFlag(cu);
      m_BinEncoder.encodeBin(CU::isIBC(cu), Ctx::IBCFlag(ctxidx));
      }
      if (!CU::isIBC(cu) && cu.cs->slice->getSPS()->getPLTMode() && cu.lwidth() <= 64 && cu.lheight() <= 64)
      {
        m_BinEncoder.encodeBin(CU::isPLT(cu), Ctx::PLTFlag(0));
      }
    }
    else
    {
      if( cu.isConsInter() )
      {
        return;
      }
      m_BinEncoder.encodeBin((CU::isIntra(cu) || CU::isPLT(cu)), Ctx::PredMode(DeriveCtx::CtxPredModeFlag(cu)));
      if (CU::isIntra(cu) || CU::isPLT(cu))
      {
        if (cu.cs->slice->getSPS()->getPLTMode() && cu.lwidth() <= 64 && cu.lheight() <= 64)
          m_BinEncoder.encodeBin(CU::isPLT(cu), Ctx::PLTFlag(0));
      }
      else
      {
        if (cu.lwidth() < 128 && cu.lheight() < 128) // disable IBC mode larger than 64x64
        {
        unsigned ctxidx = DeriveCtx::CtxIBCFlag(cu);
        m_BinEncoder.encodeBin(CU::isIBC(cu), Ctx::IBCFlag(ctxidx));
        }
      }
    }
  }
  else
  {
    if( cu.isConsInter() )
    {
      assert( CU::isInter( cu ) );
      return;
    }

    if ( cu.cs->slice->isIntra() || ( cu.lwidth() == 4 && cu.lheight() == 4 ) || cu.isConsIntra() )
    {
      if (cu.cs->slice->getSPS()->getPLTMode() && cu.lwidth() <= 64 && cu.lheight() <= 64)
        m_BinEncoder.encodeBin((CU::isPLT(cu)), Ctx::PLTFlag(0));
      return;
    }
#if JVET_P0516_PLT_BINARIZATION
    m_BinEncoder.encodeBin((CU::isIntra(cu) || CU::isPLT(cu)), Ctx::PredMode(DeriveCtx::CtxPredModeFlag(cu)));
    if ((CU::isIntra(cu) || CU::isPLT(cu)) && cu.cs->slice->getSPS()->getPLTMode() && cu.lwidth() <= 64 && cu.lheight() <= 64)
#else
    m_BinEncoder.encodeBin((CU::isIntra(cu)), Ctx::PredMode(DeriveCtx::CtxPredModeFlag(cu)));
    if (!CU::isIntra(cu) && cu.cs->slice->getSPS()->getPLTMode() && cu.lwidth() <= 64 && cu.lheight() <= 64)
#endif
    {
      m_BinEncoder.encodeBin((CU::isPLT(cu)), Ctx::PLTFlag(0));
    }
  }
}
void CABACWriter::bdpcm_mode( const CodingUnit& cu, const ComponentID compID )
{
  if( !cu.cs->sps->getBDPCMEnabledFlag() ) return;
  if( !CU::bdpcmAllowed( cu, compID ) ) return;

  m_BinEncoder.encodeBin( cu.bdpcmMode > 0 ? 1 : 0, Ctx::BDPCMMode( 0 ) );

  if( cu.bdpcmMode )
  {
    m_BinEncoder.encodeBin( cu.bdpcmMode > 1 ? 1 : 0, Ctx::BDPCMMode( 1 ) );
  }
  DTRACE( g_trace_ctx, D_SYNTAX, "bdpcm_mode() x=%d, y=%d, w=%d, h=%d, bdpcm=%d\n", cu.lumaPos().x, cu.lumaPos().y, cu.lwidth(), cu.lheight(), cu.bdpcmMode );
}


void CABACWriter::cu_pred_data( const CodingUnit& cu )
{
  if( CU::isIntra( cu ) )
  {
    intra_luma_pred_modes  ( cu );
    intra_chroma_pred_modes( cu );
    return;
  }
  if (!cu.Y().valid()) // dual tree chroma CU
  {
    return;
  }
  for( auto &pu : CU::traversePUs( cu ) )
  {
    prediction_unit( pu );
  }

  imv_mode   ( cu );
  affine_amvr_mode( cu );

  cu_gbi_flag( cu );

}

void CABACWriter::cu_gbi_flag(const CodingUnit& cu)
{
  if(!CU::isGBiIdxCoded(cu))
  {
    return;
  }

  CHECK(!(GBI_NUM > 1 && (GBI_NUM == 2 || (GBI_NUM & 0x01) == 1)), " !( GBI_NUM > 1 && ( GBI_NUM == 2 || ( GBI_NUM & 0x01 ) == 1 ) ) ");
  const uint8_t gbiCodingIdx = (uint8_t)g_GbiCodingOrder[CU::getValidGbiIdx(cu)];

  const int32_t numGBi = (cu.slice->getCheckLDC()) ? 5 : 3;
  m_BinEncoder.encodeBin((gbiCodingIdx == 0 ? 0 : 1), Ctx::GBiIdx(0));
  if(numGBi > 2 && gbiCodingIdx != 0)
  {
    const uint32_t prefixNumBits = numGBi - 2;
    const uint32_t step = 1;

    uint8_t idx = 1;
    for(int ui = 0; ui < prefixNumBits; ++ui)
    {
      if (gbiCodingIdx == idx)
      {
        m_BinEncoder.encodeBinEP(0);
        break;
      }
      else
      {
        m_BinEncoder.encodeBinEP(1);
        idx += step;
      }
    }
  }

  DTRACE(g_trace_ctx, D_SYNTAX, "cu_gbi_flag() gbi_idx=%d\n", cu.GBiIdx ? 1 : 0);
}

void CABACWriter::xWriteTruncBinCode(uint32_t symbol, uint32_t maxSymbol)
{
  int thresh;
  if (maxSymbol > 256)
  {
    int threshVal = 1 << 8;
    thresh = 8;
    while (threshVal <= maxSymbol)
    {
      thresh++;
      threshVal <<= 1;
    }
    thresh--;
  }
  else
  {
    thresh = g_tbMax[maxSymbol];
  }

  int val = 1 << thresh;
  assert(val <= maxSymbol);
  assert((val << 1) > maxSymbol);
  assert(symbol < maxSymbol);
  int b = maxSymbol - val;
  assert(b < val);
  if (symbol < val - b)
  {
    m_BinEncoder.encodeBinsEP(symbol, thresh);
  }
  else
  {
    symbol += val - b;
    assert(symbol < (val << 1));
    assert((symbol >> 1) >= val - b);
    m_BinEncoder.encodeBinsEP(symbol, thresh + 1);
  }
}

void CABACWriter::extend_ref_line(const PredictionUnit& pu)
{

  const CodingUnit& cu = *pu.cu;
  if( !cu.Y().valid() || cu.predMode != MODE_INTRA || !isLuma( cu.chType ) || cu.bdpcmMode )
  {
    return;
  }
  bool isFirstLineOfCtu = (((cu.block(COMPONENT_Y).y)&((cu.cs->sps)->getMaxCUWidth() - 1)) == 0);
  if (isFirstLineOfCtu)
  {
    return;
  }
  int multiRefIdx = pu.multiRefIdx;
  if (MRL_NUM_REF_LINES > 1)
  {
    m_BinEncoder.encodeBin(multiRefIdx != MULTI_REF_LINE_IDX[0], Ctx::MultiRefLineIdx(0));
    if (MRL_NUM_REF_LINES > 2 && multiRefIdx != MULTI_REF_LINE_IDX[0])
    {
      m_BinEncoder.encodeBin(multiRefIdx != MULTI_REF_LINE_IDX[1], Ctx::MultiRefLineIdx(1));
    }
  }
}

void CABACWriter::extend_ref_line(const CodingUnit& cu)
{

  if ( !cu.Y().valid() || cu.predMode != MODE_INTRA || !isLuma(cu.chType) || cu.bdpcmMode )
  {
    return;
  }

  const int numBlocks = CU::getNumPUs(cu);
  const PredictionUnit* pu = cu.firstPU;

  for (int k = 0; k < numBlocks; k++)
  {
    bool isFirstLineOfCtu = (((cu.block(COMPONENT_Y).y)&((cu.cs->sps)->getMaxCUWidth() - 1)) == 0);
    if (isFirstLineOfCtu)
    {
      return;
    }
    int multiRefIdx = pu->multiRefIdx;
    if (MRL_NUM_REF_LINES > 1)
    {
      m_BinEncoder.encodeBin(multiRefIdx != MULTI_REF_LINE_IDX[0], Ctx::MultiRefLineIdx(0));
      if (MRL_NUM_REF_LINES > 2 && multiRefIdx != MULTI_REF_LINE_IDX[0])
      {
        m_BinEncoder.encodeBin(multiRefIdx != MULTI_REF_LINE_IDX[1], Ctx::MultiRefLineIdx(1));
      }

    }
    pu = pu->next;
  }
}

void CABACWriter::intra_luma_pred_modes( const CodingUnit& cu )
{
  if( !cu.Y().valid() )
  {
    return;
  }

  if( cu.bdpcmMode )
  {
    cu.firstPU->intraDir[0] = cu.bdpcmMode == 2? VER_IDX : HOR_IDX;
    return;
  }

  mip_flag(cu);
  if (cu.mipFlag)
  {
    mip_pred_modes(cu);
    return;
  }
  extend_ref_line( cu );

  isp_mode( cu );

  const int numMPMs   = NUM_MOST_PROBABLE_MODES;
  const int numBlocks = CU::getNumPUs( cu );
  unsigned  mpm_preds   [4][numMPMs];
  unsigned  mpm_idxs    [4];
  unsigned  ipred_modes [4];