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  /** \file     ContextModel3DBuffer.cpp
      \brief    context model 3D buffer class
  */
  
  #include "ContextModel3DBuffer.h"
  
  //! \ingroup TLibCommon
  //! \{
  
  // ====================================================================================================================
  // Constructor / destructor / initialization / destroy
  // ====================================================================================================================
  
  ContextModel3DBuffer::ContextModel3DBuffer( UInt uiSizeZ, UInt uiSizeY, UInt uiSizeX, ContextModel *basePtr, Int &count )
  : m_sizeX  ( uiSizeX )
  , m_sizeXY ( uiSizeX * uiSizeY )
  , m_sizeXYZ( uiSizeX * uiSizeY * uiSizeZ )
  {
    // allocate 3D buffer
    m_contextModel = basePtr;
    count += m_sizeXYZ;
  }
  
  // ====================================================================================================================
  // Public member functions
  // ====================================================================================================================
  
  /**
   * Initialize 3D buffer with respect to slice type, QP and given initial probability table
   *
   * 根据 slice 的类型获取存放 initValue 的表格
   * initValue 的值和 slice 的类型是相关的。为了提高计算速度，HEVC通过查表代替直接计算。
   *
   * \param  sliceType      slice type | slice 的类型
   * \param  qp             input QP value
   * \param  ctxModel       given probability table
   */
  Void ContextModel3DBuffer::initBuffer( SliceType sliceType, Int qp, UChar* ctxModel )
  {
    // 根据当前 slice 的类型选择对应的 context
    ctxModel += sliceType * m_sizeXYZ;
  
    // 根据 sliceType 计算 initType 并将指针移动到正确的位置
    // 这个 initType 用来索引 context model，这个值由 slice_type 决定
  
    for ( Int n = 0; n < m_sizeXYZ; n++ )
    {
      // 通过查表替代直接计算
      // 完成 context 的各个状态变量的初始化工作
      m_contextModel[ n ].init( qp, ctxModel[ n ] );
      m_contextModel[ n ].setBinsCoded( 0 );
    }
  }
  
  /**
   * Calculate the cost of choosing a probability table based on the current probability of CABAC at encoder
   *
   * \param  sliceType      slice type
   * \param  qp             input QP value
   * \param  ctxModel      given probability table
   */
  UInt ContextModel3DBuffer::calcCost( SliceType sliceType, Int qp, UChar* ctxModel )
  {
    UInt cost = 0;
    ctxModel += sliceType * m_sizeXYZ;
  
    for ( Int n = 0; n < m_sizeXYZ; n++ )
    {
      ContextModel tmpContextModel;
      tmpContextModel.init( qp, ctxModel[ n ] );
  
      // Map the 64 CABAC states to their corresponding probability values
      static const Double aStateToProbLPS[] = {0.50000000, 0.47460857, 0.45050660, 0.42762859, 0.40591239, 0.38529900, 0.36573242, 0.34715948, 0.32952974, 0.31279528, 0.29691064, 0.28183267, 0.26752040, 0.25393496, 0.24103941, 0.22879875, 0.21717969, 0.20615069, 0.19568177, 0.18574449, 0.17631186, 0.16735824, 0.15885931, 0.15079198, 0.14313433, 0.13586556, 0.12896592, 0.12241667, 0.11620000, 0.11029903, 0.10469773, 0.09938088, 0.09433404, 0.08954349, 0.08499621, 0.08067986, 0.07658271, 0.07269362, 0.06900203, 0.06549791, 0.06217174, 0.05901448, 0.05601756, 0.05317283, 0.05047256, 0.04790942, 0.04547644, 0.04316702, 0.04097487, 0.03889405, 0.03691890, 0.03504406, 0.03326442, 0.03157516, 0.02997168, 0.02844963, 0.02700488, 0.02563349, 0.02433175, 0.02309612, 0.02192323, 0.02080991, 0.01975312, 0.01875000};
  
      Double probLPS          = aStateToProbLPS[ m_contextModel[ n ].getState() ];
      Double prob0, prob1;
      if (m_contextModel[ n ].getMps()==1)
      {
        prob0 = probLPS;
        prob1 = 1.0-prob0;
      }
      else
      {
        prob1 = probLPS;
        prob0 = 1.0-prob1;
      }
  
      if (m_contextModel[ n ].getBinsCoded()>0)
      {
        cost += (UInt) (prob0 * tmpContextModel.getEntropyBits( 0 ) + prob1 * tmpContextModel.getEntropyBits( 1 ));
      }
    }
  
    return cost;
  }
  //! \}
  