接下来有关HEVC的文章都是HEVC学习系列的延续，但由于序号偏多，为方便起见，就不再单独编号，直接以讨论内容作为题目了。
要研究CU级的代码，少不了要接触到这么一个类TComDataCU。为了比较顺畅地看代码，对这个类的重要成员自然需要有比较好的认识才行，这就是本文的目的，给大家提供一个共同讨论类中私有成员含义与作用的平台。
class TComDataCU
{
private:
// -------------------------------------------------------------------------------------------------------------------
// class pointers
// -------------------------------------------------------------------------------------------------------------------
TComPic* m_pcPic; ///< picture class pointer
TComSlice* m_pcSlice; ///< slice header pointer
TComPattern* m_pcPattern; ///< neighbour access class pointer
// -------------------------------------------------------------------------------------------------------------------
// CU description
// -------------------------------------------------------------------------------------------------------------------
UInt m_uiCUAddr; ///< CU address in a slice
UInt m_uiAbsIdxInLCU; ///< absolute address in a CU. It's Z scan order
UInt m_uiCUPelX; ///< CU position in a pixel (X)
UInt m_uiCUPelY; ///< CU position in a pixel (Y)
UInt m_uiNumPartition; ///< total number of minimum partitions in a CU
UChar* m_puhWidth; ///< array of widths
UChar* m_puhHeight; ///< array of heights
UChar* m_puhDepth; ///< array of depths
Int m_unitSize; ///< size of a "minimum partition"
// -------------------------------------------------------------------------------------------------------------------
// CU data
// -------------------------------------------------------------------------------------------------------------------
Bool* m_skipFlag; ///< array of skip flags
Char* m_pePartSize; ///< array of partition sizes
Char* m_pePredMode; ///< array of prediction modes
Bool* m_CUTransquantBypass; ///< array of cu_transquant_bypass flags
Char* m_phQP; ///< array of QP values
UChar* m_puhTrIdx; ///< array of transform indices
UChar* m_puhTransformSkip[3];///< array of transform skipping flags
UChar* m_puhCbf[3]; ///< array of coded block flags (CBF)
TCoeff* m_pcTrCoeffY; ///< transformed coefficient buffer (Y)
TCoeff* m_pcTrCoeffCb; ///< transformed coefficient buffer (Cb)
TCoeff* m_pcTrCoeffCr; ///< transformed coefficient buffer (Cr)
#if ADAPTIVE_QP_SELECTION
Int* m_pcArlCoeffY; ///< ARL coefficient buffer (Y)
Int* m_pcArlCoeffCb; ///< ARL coefficient buffer (Cb)
Int* m_pcArlCoeffCr; ///< ARL coefficient buffer (Cr)
Bool m_ArlCoeffIsAliasedAllocation; ///< ARL coefficient buffer is an alias of the global buffer and must not be free()'d
static Int* m_pcGlbArlCoeffY; ///< ARL coefficient buffer (Y)
static Int* m_pcGlbArlCoeffCb; ///< ARL coefficient buffer (Cb)
static Int* m_pcGlbArlCoeffCr; ///< ARL coefficient buffer (Cr)
#endif
Pel* m_pcIPCMSampleY; ///< PCM sample buffer (Y)
Pel* m_pcIPCMSampleCb; ///< PCM sample buffer (Cb)
Pel* m_pcIPCMSampleCr; ///< PCM sample buffer (Cr)
Int* m_piSliceSUMap; ///< pointer of slice ID map
std::vector<NDBFBlockInfo> m_vNDFBlock;
// -------------------------------------------------------------------------------------------------------------------
// neighbour access variables
// -------------------------------------------------------------------------------------------------------------------
TComDataCU* m_pcCUAboveLeft; ///< pointer of above-left CU
TComDataCU* m_pcCUAboveRight; ///< pointer of above-right CU
TComDataCU* m_pcCUAbove; ///< pointer of above CU
TComDataCU* m_pcCULeft; ///< pointer of left CU
TComDataCU* m_apcCUColocated[2]; ///< pointer of temporally colocated CU's for both directions
// -------------------------------------------------------------------------------------------------------------------
// coding tool information
// -------------------------------------------------------------------------------------------------------------------
UChar* m_puhLumaIntraDir; ///< array of intra directions (luma)
UChar* m_puhChromaIntraDir; ///< array of intra directions (chroma)
Bool* m_pbIPCMFlag; ///< array of intra_pcm flags
Int m_numSucIPCM; ///< the number of succesive IPCM blocks associated with the current log2CUSize
Bool m_lastCUSucIPCMFlag; ///< True indicates that the last CU is IPCM and shares the same root as the current CU.
// -------------------------------------------------------------------------------------------------------------------
// misc. variables
// -------------------------------------------------------------------------------------------------------------------
Bool m_bDecSubCu; ///< indicates decoder-mode
Double m_dTotalCost; ///< sum of partition RD costs
UInt m_uiTotalDistortion; ///< sum of partition distortion
UInt m_uiTotalBits; ///< sum of partition bits
UInt m_uiTotalBins; ///< sum of partition bins
UInt* m_uiSliceStartCU; ///< Start CU address of current slice
UInt* m_uiDependentSliceStartCU; ///< Start CU address of current slice
Char m_codedQP;
其实大部分的私有成员都有注释，再结合代码中的具体应用，它们的含义和功能十有八九是能够把握住的。
注意到，在定义这个类的TComDataCU.h文件里的最后，还定义了一个命名空间RasterAddress：
namespace RasterAddress
{
/** Check whether 2 addresses point to the same column
* \param addrA First address in raster scan order
* \param addrB Second address in raters scan order
* \param numUnitsPerRow Number of units in a row
* \return Result of test
*/
static inline Bool isEqualCol( Int addrA, Int addrB, Int numUnitsPerRow )
{
// addrA % numUnitsPerRow == addrB % numUnitsPerRow
return (( addrA ^ addrB ) & ( numUnitsPerRow - 1 ) ) == 0;
}
/** Check whether 2 addresses point to the same row
* \param addrA First address in raster scan order
* \param addrB Second address in raters scan order
* \param numUnitsPerRow Number of units in a row
* \return Result of test
*/
static inline Bool isEqualRow( Int addrA, Int addrB, Int numUnitsPerRow )
{
// addrA / numUnitsPerRow == addrB / numUnitsPerRow
return (( addrA ^ addrB ) &~ ( numUnitsPerRow - 1 ) ) == 0;
}
/** Check whether 2 addresses point to the same row or column
* \param addrA First address in raster scan order
* \param addrB Second address in raters scan order
* \param numUnitsPerRow Number of units in a row
* \return Result of test
*/
static inline Bool isEqualRowOrCol( Int addrA, Int addrB, Int numUnitsPerRow )
{
return isEqualCol( addrA, addrB, numUnitsPerRow ) | isEqualRow( addrA, addrB, numUnitsPerRow );
}
/** Check whether one address points to the first column
* \param addr Address in raster scan order
* \param numUnitsPerRow Number of units in a row
* \return Result of test
*/
static inline Bool isZeroCol( Int addr, Int numUnitsPerRow )
{
// addr % numUnitsPerRow == 0
return ( addr & ( numUnitsPerRow - 1 ) ) == 0;
}
/** Check whether one address points to the first row
* \param addr Address in raster scan order
* \param numUnitsPerRow Number of units in a row
* \return Result of test
*/
static inline Bool isZeroRow( Int addr, Int numUnitsPerRow )
{
// addr / numUnitsPerRow == 0
return ( addr &~ ( numUnitsPerRow - 1 ) ) == 0;
}
/** Check whether one address points to a column whose index is smaller than a given value
* \param addr Address in raster scan order
* \param val Given column index value
* \param numUnitsPerRow Number of units in a row
* \return Result of test
*/
static inline Bool lessThanCol( Int addr, Int val, Int numUnitsPerRow )
{
// addr % numUnitsPerRow < val
return ( addr & ( numUnitsPerRow - 1 ) ) < val;
}
/** Check whether one address points to a row whose index is smaller than a given value
* \param addr Address in raster scan order
* \param val Given row index value
* \param numUnitsPerRow Number of units in a row
* \return Result of test
*/
static inline Bool lessThanRow( Int addr, Int val, Int numUnitsPerRow )
{
// addr / numUnitsPerRow < val
return addr < val * numUnitsPerRow;
}
};
这些个函数的功能，根据函数名，再加上注释，即使可能对实现细节还不是完全清楚，也是可以把握住它们的功能的。这样就足够了，对于读代码已经是没有任何障碍了。至于是否细究细节，这个看个人了。