SEIColourTransform.cpp

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 /** \file     SEIColourTransform.cpp
     \brief    Colour transform SEI
 */

#include "SEIColourTransform.h"

#include "SEI.h"
#include "Unit.h"
#include "Buffer.h"

SEIColourTransformApply::SEIColourTransformApply()
  : m_width(0), m_height(0), m_chromaFormat(NUM_CHROMA_FORMAT), m_bitDepth(0), m_pColourTransfParams(nullptr)
{
}

void SEIColourTransformApply::create(uint32_t width, uint32_t height, ChromaFormat fmt, uint8_t bitDepth)
{
  m_width               = width;
  m_height              = height;
  m_chromaFormat        = fmt;
  m_bitDepth            = bitDepth;
  m_pColourTransfParams = new SEIColourTransformInfo;
  m_lutSize             = 1 << m_bitDepth;
  for (int i = 0; i < MAX_NUM_COMPONENT; i++)
  {
    m_mapLut[i].resize(m_lutSize, 0);
  }
}

SEIColourTransformApply::~SEIColourTransformApply()
{
  delete m_pColourTransfParams;
}

void SEIColourTransformApply::inverseColourTransform(PelStorage* transformBuf)
{
  uint8_t   numComp = m_chromaFormat ? MAX_NUM_COMPONENT : 1;
  PelBuf*   buffY   = &transformBuf->Y();
  PelBuf*   buffCb  = &transformBuf->Cb();
  PelBuf*   buffCr  = &transformBuf->Cr();

  if (numComp == 3)
  {
    if (m_pColourTransfParams->m_crossComponentFlag)
    {
      buffCb->applyChromaCTI(buffY->buf, buffY->stride, m_mapLut[COMPONENT_Cb], m_bitDepth, m_chromaFormat, false);
      buffCr->applyChromaCTI(buffY->buf, buffY->stride, m_mapLut[COMPONENT_Cr], m_bitDepth, m_chromaFormat, false);
    }
    else
    {
      buffCb->applyLumaCTI(m_mapLut[COMPONENT_Cb]); // apply direct mapping like in luma (no cross component mapping); same function, but different lut.
      buffCr->applyLumaCTI(m_mapLut[COMPONENT_Cr]);
    }
  }
  buffY->applyLumaCTI(m_mapLut[COMPONENT_Y]);
}

void SEIColourTransformApply::generateColourTransfLUTs()
{
  uint8_t numComp     = m_chromaFormat ? MAX_NUM_COMPONENT : 1;
  int numPreLutPoints = 1 << m_pColourTransfParams->m_log2NumberOfPointsPerLut;
  int dynamicRange    = 1 << m_bitDepth;
  const int orgCW     = dynamicRange / numPreLutPoints;
  int scalingPreLut   = 1 << ( 11 - (int)floorLog2(orgCW) ); // scale-up values from cfg file (chroma preLut is scaled down in cfg)

  std::vector<Pel> pivotInPoints;
  std::vector<Pel> pivotMappedPointsY(numPreLutPoints+1);
  std::vector<Pel> pivotMappedPointsX(numPreLutPoints+1);

  // Create Inverse Luma LUT - same for all possible combinations of ctiCrossComp and ctiChromaLutInferred

  std::vector<int> invScale(numPreLutPoints);

  pivotInPoints = m_pColourTransfParams->m_lut[0].lutValues;
  pivotMappedPointsX[0] = pivotInPoints[0];
  pivotMappedPointsY[0] = 0;
  for (int j = 1; j < numPreLutPoints; j++)
  {
    pivotMappedPointsX[j] = pivotMappedPointsX[j - 1] + pivotInPoints[j];
    pivotMappedPointsY[j] = j * orgCW;
  }

  for (int i = 0; i < numPreLutPoints; i++)
  {
    invScale[i] = ((int32_t)m_pColourTransfParams->m_lut[0].lutValues[i + 1] * (1 << FP_PREC) + (1 << (floorLog2(orgCW) - 1))) >> floorLog2(orgCW);
  }

  for (int i = 0; i < dynamicRange; i++)
  {
    int idx = i / orgCW;
    int tempVal = pivotMappedPointsX[idx] + ((invScale[idx] * (i - pivotMappedPointsY[idx]) + (1 << (FP_PREC - 1))) >> FP_PREC);
    m_mapLut[0][i] = Clip3((Pel)0, (Pel)(dynamicRange - 1), (Pel)(tempVal));
  }

  //  calculate chroma LUTs
  if (m_pColourTransfParams->m_crossComponentInferred == 0)
  {
    for (int i = 1; i < numComp; i++)
    { // loop for U and V
      if (m_pColourTransfParams->m_crossComponentFlag == 1)
      {
        // cross-component U and V LUT
        for (int j = 0; j < dynamicRange; j++)
        {
          int     idx     = j / orgCW;
          int  slope = scalingPreLut * (m_pColourTransfParams->m_lut[i].lutValues[idx + 1] - m_pColourTransfParams->m_lut[i].lutValues[idx]);
          m_mapLut[i][j] = scalingPreLut * m_pColourTransfParams->m_lut[i].lutValues[idx] + slope * (j - pivotMappedPointsY[idx]) / orgCW;
        }
      }
      else
      {
        // intra-component Chroma (U and V) LUT
        // initialize pivot points
        pivotInPoints = m_pColourTransfParams->m_lut[i].lutValues;
        pivotMappedPointsX[0] = pivotInPoints[0];
        for (int j = 1; j <= numPreLutPoints; j++)
        {
          pivotMappedPointsX[j] = pivotMappedPointsX[j-1] + pivotInPoints[j];
        }

        for (int i = 0; i < numPreLutPoints; i++)
        {
          invScale[i] = ((int32_t)m_pColourTransfParams->m_lut[0].lutValues[i + 1] * (1 << FP_PREC) + (1 << (floorLog2(orgCW) - 1))) >> floorLog2(orgCW);
        }

        for (int j = 0; j < dynamicRange; j++)
        {
          int idx = j / orgCW;
          int tempVal = pivotMappedPointsX[idx] + ((invScale[idx] * (j - pivotMappedPointsY[idx]) + (1 << (FP_PREC - 1))) >> FP_PREC);
          m_mapLut[i][j] = Clip3((Pel)0, (Pel)(dynamicRange - 1), (Pel)(tempVal));
        }
      }
    }
  }
  else
  {
    int chrOffset = m_pColourTransfParams->m_chromaOffset;

    std::vector<int> chromaAdjHelpLUT (numPreLutPoints);
    for (int i = 0; i < numPreLutPoints; i++)
    {
      chromaAdjHelpLUT[i] = (m_pColourTransfParams->m_lut[0].lutValues[i + 1] == 0) ? (1 << CSCALE_FP_PREC) : ((int32_t)((m_pColourTransfParams->m_lut[0].lutValues[i + 1] + chrOffset) * (1 << FP_PREC) / orgCW));
    }

    // generate smoothed chroma LUT as done by JVET-U0078
    std::vector<int> interpLut(numPreLutPoints + 1);
    for (int i = 1; i < numPreLutPoints; i++)
    {
      interpLut[i] = (chromaAdjHelpLUT[i] + chromaAdjHelpLUT[i - 1] + 1) / 2;
    }
    interpLut[0]                = chromaAdjHelpLUT[0];
    interpLut[numPreLutPoints]  = chromaAdjHelpLUT[numPreLutPoints - 1];

    for (int i = 0; i < dynamicRange; i++)
    {
      int idx = i / orgCW;
      int slope = interpLut[idx + 1] - interpLut[idx];
      m_mapLut[1][i] = interpLut[idx] + slope * (i - pivotMappedPointsY[idx]) / orgCW;
      m_mapLut[2][i] = m_mapLut[1][i];
    }
  }
}