text: /* -----------------------------------------------------------------------------
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  the Software are granted under this license.
  
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  especially patent licenses, a separate Agreement needs to be closed. 
  For more information please contact:
  
  Fraunhofer Heinrich Hertz Institute
  Einsteinufer 37
  10587 Berlin, Germany
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  vvc@hhi.fraunhofer.de
  
  Copyright (c) 2018-2022, Fraunhofer-Gesellschaft zur Förderung der angewandten Forschung e.V. 
  All rights reserved.
  
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   * Redistributions of source code must retain the above copyright notice,
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     and/or other materials provided with the distribution.
   * Neither the name of Fraunhofer nor the names of its contributors may
     be used to endorse or promote products derived from this software without
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  AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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  ------------------------------------------------------------------------------------------- */
  
  /** \file     UnitPartitioner.h
   *  \brief    Provides a class for partitioning management
   */
  
  #include "UnitPartitioner.h"
  
  #include "CodingStructure.h"
  #include "Unit.h"
  #include "Slice.h"
  #include "UnitTools.h"
  #include "Picture.h"
  
  namespace vvdec
  {
  
  PartLevel::PartLevel()
  : split               ( CU_DONT_SPLIT )
  , parts               (               )
  , idx                 ( 0u            )
  , cuAbove             ( nullptr       )
  , cuLeft              ( nullptr       )
  , modeType            ( MODE_TYPE_ALL )
  , qgEnable            ( true          )
  , qgChromaEnable      ( true          )
  {
  }
  
  void PartLevel::init()
  {
    split           = CU_DONT_SPLIT;
    idx             = 0u;
    cuAbove         = nullptr;
    cuLeft          = nullptr;
    modeType        = MODE_TYPE_ALL;
    qgEnable        = true;
    qgChromaEnable  = true;
  }
  
  //////////////////////////////////////////////////////////////////////////
  // Partitioner class
  //////////////////////////////////////////////////////////////////////////
  
  SplitSeries Partitioner::getSplitSeries() const
  {
    SplitSeries splitSeries = 0;
    SplitSeries depth = 0;
  
    for( const auto &level : m_partStack )
    {
      if( level.split == CTU_LEVEL ) continue;
      else splitSeries += static_cast< SplitSeries >( level.split ) << ( depth * SPLIT_DMULT );
  
      depth++;
  
      if( depth >= 3 ) break;
    }
  
    return splitSeries;
  }
  
  bool Partitioner::isSepTree( const CodingStructure &cs ) const
  {
    return treeType != TREE_D || isDualITree;
  }
  
  void Partitioner::setCUData( CodingUnit& cu )
  {
    cu.depth       = currDepth;
    cu.qtDepth     = currQtDepth;
    cu.splitSeries = getSplitSeries();
  }
  
  static void setNeighborCu( PartLevel& level, Partitioner& p, const CodingStructure& cs )
  {
    const ChannelType chType = p.treeType == TREE_C ? CH_C : p.chType;
    const Position   &pos    = p.currArea().blocks[chType].pos();
  
    // get above depth
    level.cuAbove  = cs.getCURestricted( pos.offset( 0, -1 ), pos, p.currSliceIdx, p.currTileIdx, chType );
  
    // get left depth
    level.cuLeft   = cs.getCURestricted( pos.offset( -1, 0 ), pos, p.currSliceIdx, p.currTileIdx, chType );
  }
  
  
  void Partitioner::initCtu( const UnitArea& ctuArea, const ChannelType _chType, const CodingStructure& cs, const Slice& slice )
  {
    this->slice = &slice;
  #if _DEBUG
    m_currArea = ctuArea;
  #endif
    currDepth   = 0;
    currTrDepth = 0;
    currMtDepth = 0;
    currQtDepth = 0;
    currSubdiv  = 0;
    chType      = _chType;
    currQgPos   = ctuArea.lumaPos();
    currQgChromaPos = ctuArea.chromaFormat != CHROMA_400 ? ctuArea.chromaPos() : Position();
    currImplicitBtDepth = 0;
  
    currSliceIdx = slice.getIndependentSliceIdx();
    currTileIdx  = cs.pps->getTileIdx( ctuArea.lumaPos() );
  
    m_partBufIdx = 1;
    m_partStack.resize_noinit( 1 );
    m_partStack.back().split = CTU_LEVEL;
    m_partStack.back().parts = m_partBuf;
    m_partStack.back().parts[0] = ctuArea;
    m_partStack.back().numParts = 1;
    treeType = TREE_D;
    modeType = MODE_TYPE_ALL;
  
    setNeighborCu( m_partStack.back(), *this, cs );
  
    const SPS& sps = *cs.sps;
  #if GDR_ADJ
    isDualITree = slice.isIntra() && slice.getSPS()->getUseDualITree();
    const int valIdx = slice.isIntra() ? ( !isDualITree? 0 : ( _chType << 1 ) ) : 1;
  #else
    isDualITree = slice.isIRAP() && slice.getSPS()->getUseDualITree();
    const int valIdx = slice.isIRAP() ? ( _chType << 1 ) : 1;
  #endif
  
    const unsigned minBtSizeArr[] = { 1u << sps.getLog2MinCodingBlockSize(), 1u << sps.getLog2MinCodingBlockSize(), 1u << sps.getLog2MinCodingBlockSize() };
    const unsigned minTtSizeArr[] = { 1u << sps.getLog2MinCodingBlockSize(), 1u << sps.getLog2MinCodingBlockSize(), 1u << sps.getLog2MinCodingBlockSize() };
  
    minBtSize = minBtSizeArr[valIdx];
    minTtSize = minTtSizeArr[valIdx];
  
    if( cs.picHeader->getSplitConsOverrideFlag() )
    {
      maxBTD    = slice.getPicHeader()->getMaxMTTHierarchyDepth( slice.getSliceType(), _chType );
      maxBtSize = slice.getPicHeader()->getMaxBTSize( slice.getSliceType(), _chType );
      maxTtSize = slice.getPicHeader()->getMaxTTSize( slice.getSliceType(), _chType );
      minQtSize = slice.getPicHeader()->getMinQTSize( slice.getSliceType(), _chType );
    }
    else
    {
      const unsigned maxBtDepthArr[] = { sps.getMaxBTDepthI(), sps.getMaxBTDepth(), sps.getMaxBTDepthIChroma() };
      const unsigned maxBtSizeArr[]  = { sps.getMaxBTSizeI(), sps.getMaxBTSize(), sps.getMaxBTSizeIChroma() };
      const unsigned maxTtSizeArr[]  = { sps.getMaxTTSizeI(), sps.getMaxTTSize(), sps.getMaxTTSizeIChroma() };
      const unsigned minQtSizeArr[]  = { sps.getMinQTSize( I_SLICE, CHANNEL_TYPE_LUMA ), sps.getMinQTSize( B_SLICE, CHANNEL_TYPE_LUMA ), sps.getMinQTSize( I_SLICE, CHANNEL_TYPE_CHROMA ) };
  
      maxBTD    = maxBtDepthArr[valIdx];
      maxBtSize = maxBtSizeArr [valIdx];
      maxTtSize = maxTtSizeArr [valIdx];
      minQtSize = minQtSizeArr [valIdx];
    }
  
    maxTrSize = cs.sps->getMaxTbSize();
  }
  
  void Partitioner::splitCurrArea( const PartSplit split, const CodingStructure& cs )
  {
    const bool isImplicit = !cs.picture->Y().contains( currArea().Y().bottomRight() );
    const UnitArea& area  = currArea();
    bool qgEnable         = currQgEnable();
    bool qgChromaEnable   = currQgChromaEnable();
  
    PartLevel &last = m_partStack.back();
    m_partStack.resize_noinit( m_partStack.size() + 1 );
    PartLevel& back = m_partStack.back();
    back.init();
    back.parts = &m_partBuf[m_partBufIdx];
    int numParts;
  
    if     ( split <= CU_TRIV_SPLIT )
      numParts = PartitionerImpl::getCUSubPartitions     ( area, cs, split, back.parts );
    else if( split == TU_MAX_TR_SPLIT )
      numParts = PartitionerImpl::getMaxTuTiling         ( area, cs,        back.parts );
    else if( split >= SBT_VER_HALF_POS0_SPLIT && split <= SBT_HOR_QUAD_POS1_SPLIT )
      numParts = PartitionerImpl::getSbtTuTiling         ( area, cs, split, back.parts );
    else /* if( split == TU_1D_HORZ_SPLIT || split == TU_1D_VERT_SPLIT ) */
      numParts = PartitionerImpl::getTUIntraSubPartitions( area, cs, isDualITree, split, back.parts, treeType );
  
    back.numParts = numParts;
    m_partBufIdx += numParts;
  
    CHECK( m_partBufIdx > partBufSize, "Partition buffer overflow" );
  
    switch( split )
    {
    case CU_QUAD_SPLIT:
      currTrDepth = 0;
      CHECKD( currMtDepth > 0, "Cannot split a non-square area other than with a binary split" );
      currMtDepth = 0;
      currQtDepth++;
      currSubdiv ++;
      break;
    case CU_HORZ_SPLIT:
    case CU_VERT_SPLIT:
      currTrDepth = 0;
      if( isImplicit ) currImplicitBtDepth++;
      currMtDepth++;
      break;
    case CU_TRIH_SPLIT:
    case CU_TRIV_SPLIT:
      currTrDepth = 0;
      currMtDepth++;
      currSubdiv ++;
      break;
    case TU_MAX_TR_SPLIT:
    case SBT_VER_HALF_POS0_SPLIT:
    case SBT_VER_HALF_POS1_SPLIT:
    case SBT_HOR_HALF_POS0_SPLIT:
    case SBT_HOR_HALF_POS1_SPLIT:
    case SBT_VER_QUAD_POS0_SPLIT:
    case SBT_VER_QUAD_POS1_SPLIT:
    case SBT_HOR_QUAD_POS0_SPLIT:
    case SBT_HOR_QUAD_POS1_SPLIT:
    case TU_1D_HORZ_SPLIT:
    case TU_1D_VERT_SPLIT:
      currTrDepth++;
      break;
    default:
      THROW( "Unknown split mode" );
      break;
    }
  
    currDepth++;
    currSubdiv++;
    
    qgEnable       &= ( currSubdiv <= slice->getCuQpDeltaSubdiv() );
    qgChromaEnable &= ( currSubdiv <= slice->getCuChromaQpOffsetSubdiv() );
    if( qgEnable )
      currQgPos = currArea().lumaPos();
    if( qgChromaEnable )
      currQgChromaPos = currArea().chromaPos();
    
    back.qgEnable       = qgEnable;
    back.qgChromaEnable = qgChromaEnable;
    back.split          = split;
    back.modeType       = modeType;
    back.cuAbove        = last.cuAbove;
    back.cuLeft         = last.cuLeft;
  
  #if _DEBUG
  
    m_currArea = m_partStack.back().parts[0];
  #endif
  }
  
  void Partitioner::canSplit( const CodingStructure &cs, bool& canNo, bool& canQt, bool& canBh, bool& canBv, bool& canTh, bool& canTv ) const
  {
    canNo = canQt = canBh = canTh = canBv = canTv = true;
    bool canBtt = currMtDepth < ( maxBTD + currImplicitBtDepth );
  
    // the minimal and maximal sizes are given in luma samples
    const CompArea&  area  = currArea().Y();
    const CompArea  *areaC = (chType == CHANNEL_TYPE_CHROMA) ? &(currArea().Cb()) : nullptr;
    const PartLevel& level = m_partStack.back();
  
    if( isDualITree && ( area.width > 64 || area.height > 64 ) )
    {
      canQt                                 = true;
      canNo = canBh = canTh = canBv = canTv = false;
  
      return;
    }
  
    if( treeType == TREE_C )
    {
      canQt = canBh = canTh = canBv = canTv = false;
      return;
    }
  
    const PartSplit lastSplit   = level.split;
    const bool      isTrInPic   = area.x + area.width  <= cs.picture->lwidth();
    const bool      isBlInPic   = area.y + area.height <= cs.picture->lheight();
    const bool      isImplicit  = !isBlInPic || !isTrInPic;
  
    // don't allow QT-splitting below a BT split
    if( lastSplit != CTU_LEVEL && lastSplit != CU_QUAD_SPLIT ) canQt = false;
    // minQtSize is in luma samples unit
    const unsigned minQTThreshold = minQtSize;
    if( area.width <= minQTThreshold )                         canQt = false;
  
    if( areaC && areaC->width <= MIN_DUALTREE_CHROMA_WIDTH ) canQt = false;
    if( isImplicit )
    {
      const bool isBtAllowed = area.width <= maxBtSize && area.height <= maxBtSize && area.width <= MAX_TB_SIZEY && area.height <= MAX_TB_SIZEY;
      canNo  = canTh = canTv = false;
      
      canQt |= !isBtAllowed;
      canBh  =  isBtAllowed && !isBlInPic && ( isTrInPic || !canQt );
      canBv  =  isBtAllowed &&  isBlInPic &&  !isTrInPic;
      canBv &= ( !areaC || areaC->width > 4 );
      canQt |= !canBh && !canBv;
      return;
    }
  
    canBtt &=   area.width >  minBtSize || area.height >  minBtSize   ||   area.width >  minTtSize || area.height >  minTtSize;
    canBtt &= ( area.width <= maxBtSize && area.height <= maxBtSize ) || ( area.width <= maxTtSize && area.height <= maxTtSize );
  
    if( !canBtt )
    {
      canBh = canTh = canBv = canTv = false;
      return;
    }
  
    const bool allowModeBt = modeType != MODE_TYPE_INTER || area.area() != 32;
    const bool allowModeTt = modeType != MODE_TYPE_INTER || area.area() != 64;
  
    if( area.width > maxBtSize || area.height > maxBtSize || !allowModeBt )
    {
      canBh = canBv = false;
    }
    else
    {
      if( ( lastSplit == CU_TRIH_SPLIT || lastSplit == CU_TRIV_SPLIT ) && level.idx == 1 )
      {
        const PartSplit parlSplit = lastSplit == CU_TRIH_SPLIT ? CU_HORZ_SPLIT : CU_VERT_SPLIT;
  
        canBh = parlSplit != CU_HORZ_SPLIT;
        canBv = parlSplit != CU_VERT_SPLIT;
      }
  
      // specific check for BT splits
      canBh &= ( area.height > minBtSize && area.height <= maxBtSize );
      canBh &= ( area.width <= MAX_TU_SIZE_FOR_PROFILE || area.height > MAX_TU_SIZE_FOR_PROFILE );
  
      canBv &= ( area.width > minBtSize && area.width <= maxBtSize );
      canBv &= ( area.width > MAX_TU_SIZE_FOR_PROFILE || area.height <= MAX_TU_SIZE_FOR_PROFILE );
    }
  
    if( area.width > maxTtSize || area.height > maxTtSize || !allowModeTt || !( area.width <= MAX_TU_SIZE_FOR_PROFILE && area.height <= MAX_TU_SIZE_FOR_PROFILE ) )
    {
      canTh = canTv = false;
  
      if( !canBh && !canBv ) return;
    }
    else
    {
      canTh &= !( area.height <= 2 * minTtSize );
      canTv &= !( area.width  <= 2 * minTtSize );
    }
  
    if( areaC )
    {
      canBh &=  ( areaC->width * areaC->height > MIN_DUALTREE_CHROMA_SIZE );
      canTh &=  ( areaC->width * areaC->height > MIN_DUALTREE_CHROMA_SIZE*2 );
      canBv &=  ( areaC->width * areaC->height > MIN_DUALTREE_CHROMA_SIZE   && areaC->width > 4 );
      canTv &=  ( areaC->width * areaC->height > MIN_DUALTREE_CHROMA_SIZE*2 && areaC->width > 8 );
    }
  }
  
  bool Partitioner::canSplit( const PartSplit split, const CodingStructure &cs, bool isISP ) const
  {
    CHECKD( split < TU_MAX_TR_SPLIT, "This function should only be used for transformation split handling!" );
  
    if( split == TU_MAX_TR_SPLIT )
    {
      const CompArea& area = currArea().Y();
  
      return area.width > maxTrSize || area.height > maxTrSize;
    }
    else
    {
      return currTrDepth == 0;
    }
    
    return false;
  }
  
  void Partitioner::exitCurrSplit( const CodingStructure& cs )
  {
    const PartSplit currSplit = m_partStack.back().split;
    const int       currIndex = m_partStack.back().idx;
    const int       numParts  = m_partStack.back().numParts;
  
    m_partStack.pop_back();
    m_partBufIdx -= numParts;
  
    const bool isImplicit     = !cs.picture->Y().contains( currArea().Y().bottomRight() );
  
    CHECKD( currDepth == 0, "depth is '0', although a split was performed" );
  
    currDepth --;
    currSubdiv--;
  
    if( currQgEnable() )
      currQgPos = currArea().lumaPos();
    if( currArea().chromaFormat != CHROMA_400 && currQgChromaEnable() )
      currQgChromaPos = currArea().chromaPos();
  
  #if _DEBUG
    m_currArea = m_partStack.back().parts[m_partStack.back().idx];
  #endif
  
    if( currSplit == CU_HORZ_SPLIT || currSplit == CU_VERT_SPLIT || currSplit == CU_TRIH_SPLIT || currSplit == CU_TRIV_SPLIT )
    {
      CHECKD( currMtDepth == 0, "MT depth is '0', athough a BT split was performed" );
  
      currMtDepth--;
      if( isImplicit ) currImplicitBtDepth--;
      
      if( ( currSplit == CU_TRIH_SPLIT || currSplit == CU_TRIV_SPLIT ) && currIndex != 1 )
      {
        currSubdiv--;
      }
    }
    else if( currSplit == TU_MAX_TR_SPLIT )
    {
      CHECKD( currTrDepth == 0, "TR depth is '0', although a TU split was performed" );
  
      currTrDepth--;
    }
    else if( currSplit >= SBT_VER_HALF_POS0_SPLIT && currSplit <= SBT_HOR_QUAD_POS1_SPLIT )
    {
      CHECKD( currTrDepth == 0, "TR depth is '0', although a TU split was performed" );
  
      currTrDepth--;
    }
    else if( currSplit == TU_1D_HORZ_SPLIT || currSplit == TU_1D_VERT_SPLIT )
    {
      currTrDepth--;
    }
    else
    {
      CHECKD( currTrDepth  > 0, "RQT found with QTBT partitioner" );
      CHECKD( currQtDepth == 0, "QT depth is '0', although a QT split was performed" );
  
      currQtDepth--;
      currSubdiv --;
    }
  }
  
  bool Partitioner::nextPart( const CodingStructure &cs, bool autoPop /*= false*/ )
  {
          PartLevel& back   =   m_partStack.back();
    const unsigned currIdx  = ++back.idx;
    const PartSplit currSpl =   back.split;
  
    if( currIdx < back.numParts )
    {
  #if _DEBUG
      m_currArea = back.parts[currIdx];
  #endif
      if( currSpl <= CU_TRIV_SPLIT )
        setNeighborCu( back, *this, cs );
      
      if( currSpl == CU_TRIH_SPLIT || currSpl == CU_TRIV_SPLIT )
      {
        if( currIdx == 1 ) currSubdiv--;
        else               currSubdiv++;
      }
  
      if( currQgEnable() )
        currQgPos = currArea().lumaPos();
      if( currQgChromaEnable() )
        currQgChromaPos = currArea().chromaPos();
  
      return true;
    }
    else
    {
      if( autoPop ) exitCurrSplit( cs );
      return false;
    }
  }
  
  void Partitioner::updateNeighbors( const CodingStructure& cs )
  {
    setNeighborCu( m_partStack.back(), *this, cs );
  }
  
  bool Partitioner::hasNextPart() const
  {
    return ( ( m_partStack.back().idx + 1 ) < m_partStack.back().numParts );
  }
  
  //////////////////////////////////////////////////////////////////////////
  // Partitioner methods describing the actual partitioning logic
  //////////////////////////////////////////////////////////////////////////
  
  int PartitionerImpl::getCUSubPartitions( const UnitArea &cuArea, const CodingStructure &cs, const PartSplit _splitType, Partitioning& dst )
  {
    const PartSplit splitType = _splitType;
  
    if( splitType == CU_QUAD_SPLIT )
    {
      Partitioning& sub = dst;
  
      for( uint32_t i = 0; i < 4; i++ )
      {
        sub[i] = cuArea;
  
        for( auto &blk : sub[i].blocks )
        {
          blk.height >>= 1;
          blk.width  >>= 1;
          if( i >= 2 ) blk.y += blk.height;
          if( i &  1 ) blk.x += blk.width;
        }
  
        CHECK( sub[i].lumaSize().height < MIN_TU_SIZE, "the split causes the block to be smaller than the minimal TU size" );
      }
  
      return 4;
    }
    else if( splitType == CU_HORZ_SPLIT )
    {
      Partitioning& sub = dst;
  
      for (uint32_t i = 0; i < 2; i++)
      {
        sub[i] = cuArea;
  
        for (auto &blk : sub[i].blocks)
        {
          blk.height >>= 1;
          if (i == 1) blk.y += blk.height;
        }
  
        CHECK(sub[i].lumaSize().height < MIN_TU_SIZE, "the cs split causes the block to be smaller than the minimal TU size");
      }
  
      return 2;
    }
    else if( splitType == CU_VERT_SPLIT )
    {
      Partitioning& sub = dst;
  
      for( uint32_t i = 0; i < 2; i++ )
      {
        sub[i] = cuArea;
  
        for( auto &blk : sub[i].blocks )
        {
          blk.width >>= 1;
          if( i == 1 ) blk.x += blk.width;
        }
  
        CHECK( sub[i].lumaSize().width < MIN_TU_SIZE, "the split causes the block to be smaller than the minimal TU size" );
      }
  
      return 2;
    }
    else if( splitType == CU_TRIH_SPLIT )
    {
      Partitioning& sub = dst;
  
      for( int i = 0; i < 3; i++ )
      {
        sub[i] = cuArea;
  
        for( auto &blk : sub[i].blocks )
        {
          blk.height >>= 1;
          if( ( i + 1 ) & 1 ) blk.height >>= 1;
          if( i == 1 )        blk.y       +=     blk.height / 2;
          if( i == 2 )        blk.y       += 3 * blk.height;
        }
  
        CHECK( sub[i].lumaSize().height < MIN_TU_SIZE, "the cs split causes the block to be smaller than the minimal TU size" );
      }
  
      return 3;
    }
    else if( splitType == CU_TRIV_SPLIT )
    {
      Partitioning& sub = dst;
  
      for( int i = 0; i < 3; i++ )
      {
        sub[i] = cuArea;
  
        for( auto &blk : sub[i].blocks )
        {
          blk.width >>= 1;
  
          if( ( i + 1 ) & 1 ) blk.width >>= 1;
          if( i == 1 )        blk.x      +=     blk.width / 2;
          if( i == 2 )        blk.x      += 3 * blk.width;
        }
  
        CHECK( sub[i].lumaSize().width < MIN_TU_SIZE, "the cs split causes the block to be smaller than the minimal TU size" );
      }
  
      return 3;
    }
    else
    {
      THROW( "Unknown CU sub-partitioning" );
    }
  }
  
  int PartitionerImpl::getTUIntraSubPartitions( const UnitArea &tuArea, const CodingStructure &cs, const bool isDualTree, const PartSplit splitType, Partitioning &sub, const TreeType treeType )
  {
    uint32_t nPartitions;
    uint32_t splitDimensionSize = CU::getISPSplitDim( tuArea.lumaSize().width, tuArea.lumaSize().height, splitType );
  
    if( splitType == TU_1D_HORZ_SPLIT )
    {
      nPartitions = tuArea.lumaSize().height >> getLog2(splitDimensionSize);
  
      for( uint32_t i = 0; i < nPartitions; i++ )
      {
        sub[i] = tuArea;
        CompArea& blkY = sub[i].blocks[COMPONENT_Y];
  
        blkY.height = splitDimensionSize;
        blkY.y = i > 0 ? sub[i - 1].blocks[COMPONENT_Y].y + splitDimensionSize : blkY.y;
  
        CHECK( sub[i].lumaSize().height < 1, "the cs split causes the block to be smaller than the minimal TU size" );
      }
    }
    else if( splitType == TU_1D_VERT_SPLIT )
    {
      nPartitions = tuArea.lumaSize().width >> getLog2(splitDimensionSize);
  
      for( uint32_t i = 0; i < nPartitions; i++ )
      {
        sub[i] = tuArea;
        CompArea& blkY = sub[i].blocks[COMPONENT_Y];
  
        blkY.width = splitDimensionSize;
        blkY.x = i > 0 ? sub[i - 1].blocks[COMPONENT_Y].x + splitDimensionSize : blkY.x;
        CHECK( sub[i].lumaSize().width < 1, "the split causes the block to be smaller than the minimal TU size" );
      }
    }
    else
    {
      THROW( "Unknown TU sub-partitioning" );
    }
    //we only partition luma, so there is going to be only one chroma tu at the end (unless it is dual tree, in which case there won't be any chroma components)
    uint32_t partitionsWithoutChroma = (cs.area.chromaFormat == CHROMA_400) ? 0 : (isDualTree ? nPartitions : nPartitions - 1);
    for( uint32_t i = 0; i < partitionsWithoutChroma; i++ )
    {
      CompArea& blkCb = sub[i].blocks[COMPONENT_Cb];
      CompArea& blkCr = sub[i].blocks[COMPONENT_Cr];
      blkCb = CompArea();
      blkCr = CompArea();
    }
  
    return nPartitions;
  }
  
  
  static const int g_rsScanToZ_w4[16] =
  {
     0,  1,  4,  5, // wouldn't work for 128x32 blocks, but those are forbidden bcs of VPDU constraints
     2,  3,  6,  7, // correct ordering for 128x64 (TU32)
     8,  9, 12, 13,
    10, 11, 14, 15, // correct ordering for 128x128 (TU32)
  };
  
  static const int g_rsScanToZ_w2[8] =
  {
     0,  1, // correct ordering for 64x32 (TU32) and 128x64 (TU64)
     2,  3, // correct ordering for 64x64 (TU32) and 128x128 (TU64)
     4,  5,
     6,  7, // correct ordering for 32x64 (TU32) and 64x128 (TU64)
  };
  
  static const int g_rsScanToZ_w1[4] =
  {
     0, // no tiling, never used
     1, // correct ordering for 64x32 (TU32) and 128x64 (TU64)
     2,
     3, // correct ordering for 128x32 (TU32)
  };
  
  static const int* g_rsScanToZ[3] = { g_rsScanToZ_w1, g_rsScanToZ_w2, g_rsScanToZ_w4 };
  
  int PartitionerImpl::getMaxTuTiling( const UnitArea &cuArea, const CodingStructure &cs, Partitioning& dst )
  {
    const Size area     = cuArea.lumaSize();
    const int maxTrSize = cs.sps->getMaxTbSize();
    const int numTilesH = std::max<int>( 1, area.width  / maxTrSize );
    const int numTilesV = std::max<int>( 1, area.height / maxTrSize );
    const int numTiles  = numTilesH * numTilesV;
    const int numLog2H  = getLog2( numTilesH );
    const int* rsScanToZ = g_rsScanToZ[numLog2H];
  
    CHECK( numTiles > MAX_CU_TILING_PARTITIONS, "CU partitioning requires more partitions than available" );
  
    Partitioning& ret = dst;
  
    for( int i = 0; i < numTiles; i++ )
    {
      ret[i] = cuArea;
  
      const int zid = rsScanToZ[i];
  
      const int y = zid >>         numLog2H;
      const int x = zid & ( ( 1 << numLog2H) - 1 );
  
      UnitArea& tile = ret[i];
  
      for( CompArea &comp : tile.blocks )
      {
        if( !comp.valid() ) continue;
  
        comp.width  /= numTilesH;
        comp.height /= numTilesV;
  
        comp.x += comp.width  * x;
        comp.y += comp.height * y;
      }
    }
  
    return numTiles;
  }
  
  int PartitionerImpl::getSbtTuTiling( const UnitArea& cuArea, const CodingStructure &cs, const PartSplit splitType, Partitioning& dst )
  {
    Partitioning& ret = dst;
    int numTiles      = 2;
    int widthFactor, heightFactor, xOffsetFactor, yOffsetFactor;
  
    CHECK( !(splitType >= SBT_VER_HALF_POS0_SPLIT && splitType <= SBT_HOR_QUAD_POS1_SPLIT), "wrong" );
  
    for( int i = 0; i < numTiles; i++ )
    {
      ret[i] = cuArea;
  
      if( splitType >= SBT_VER_QUAD_POS0_SPLIT )
      {
        if( splitType == SBT_HOR_QUAD_POS0_SPLIT || splitType == SBT_HOR_QUAD_POS1_SPLIT )
        {
          widthFactor   = 4;
          xOffsetFactor = 0;
          heightFactor  = ( ( i == 0 &&        splitType == SBT_HOR_QUAD_POS0_SPLIT ) || ( i == 1 && splitType == SBT_HOR_QUAD_POS1_SPLIT ) ) ? 1 : 3;
          yOffsetFactor =   ( i == 0 ) ? 0 : ( splitType == SBT_HOR_QUAD_POS0_SPLIT ? 1 : 3 );
        }
        else
        {
          widthFactor   = ( ( i == 0 &&        splitType == SBT_VER_QUAD_POS0_SPLIT ) || ( i == 1 && splitType == SBT_VER_QUAD_POS1_SPLIT ) ) ? 1 : 3;
          xOffsetFactor =   ( i == 0 ) ? 0 : ( splitType == SBT_VER_QUAD_POS0_SPLIT ? 1 : 3 );
          heightFactor  = 4;
          yOffsetFactor = 0;
        }
      }
      else
      {
        if( splitType == SBT_HOR_HALF_POS0_SPLIT || splitType == SBT_HOR_HALF_POS1_SPLIT )
        {
          widthFactor   = 4;
          xOffsetFactor = 0;
          heightFactor  = 2;
          yOffsetFactor = ( i == 0 ) ? 0 : 2;
        }
        else
        {
          widthFactor   = 2;
          xOffsetFactor = ( i == 0 ) ? 0 : 2;
          heightFactor  = 4;
          yOffsetFactor = 0;
        }
      }
  
      UnitArea& tile = ret[i];
  
      for( CompArea &comp : tile.blocks )
      {
        if( !comp.valid() ) continue;
  
        comp.x     += ( comp.width  * xOffsetFactor ) >> 2;
        comp.y     += ( comp.height * yOffsetFactor ) >> 2;
        comp.width  = ( comp.width  * widthFactor   ) >> 2;
        comp.height = ( comp.height * heightFactor  ) >> 2;
      }
    }
  
    return numTiles;
  }
  
  }
  