libbpg/jctvc/TLibEncoder/TEncBinCoderCABAC.cpp

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/** \file     TEncBinCoderCABAC.cpp
    \brief    binary entropy encoder of CABAC
*/

#include "TEncBinCoderCABAC.h"
#include "TLibCommon/TComRom.h"
#include "TLibCommon/Debug.h"

//! \ingroup TLibEncoder
//! \{


TEncBinCABAC::TEncBinCABAC()
: m_pcTComBitIf( 0 )
, m_binCountIncrement( 0 )
#if FAST_BIT_EST
, m_fracBits( 0 )
#endif
{
}

TEncBinCABAC::~TEncBinCABAC()
{
}

Void TEncBinCABAC::init( TComBitIf* pcTComBitIf )
{
  m_pcTComBitIf = pcTComBitIf;
}

Void TEncBinCABAC::uninit()
{
  m_pcTComBitIf = 0;
}

Void TEncBinCABAC::start()
{
  m_uiLow            = 0;
  m_uiRange          = 510;
  m_bitsLeft         = 23;
  m_numBufferedBytes = 0;
  m_bufferedByte     = 0xff;
#if FAST_BIT_EST
  m_fracBits         = 0;
#endif
}

Void TEncBinCABAC::finish()
{
  if ( m_uiLow >> ( 32 - m_bitsLeft ) )
  {
    //assert( m_numBufferedBytes > 0 );
    //assert( m_bufferedByte != 0xff );
    m_pcTComBitIf->write( m_bufferedByte + 1, 8 );
    while ( m_numBufferedBytes > 1 )
    {
      m_pcTComBitIf->write( 0x00, 8 );
      m_numBufferedBytes--;
    }
    m_uiLow -= 1 << ( 32 - m_bitsLeft );
  }
  else
  {
    if ( m_numBufferedBytes > 0 )
    {
      m_pcTComBitIf->write( m_bufferedByte, 8 );
    }
    while ( m_numBufferedBytes > 1 )
    {
      m_pcTComBitIf->write( 0xff, 8 );
      m_numBufferedBytes--;
    }
  }
  m_pcTComBitIf->write( m_uiLow >> 8, 24 - m_bitsLeft );
}

Void TEncBinCABAC::flush()
{
  encodeBinTrm(1);
  finish();
  m_pcTComBitIf->write(1, 1);
  m_pcTComBitIf->writeAlignZero();

  start();
}

/** Reset BAC register and counter values.
 * \returns Void
 */
Void TEncBinCABAC::resetBac()
{
  start();
}

/** Encode PCM alignment zero bits.
 * \returns Void
 */
Void TEncBinCABAC::encodePCMAlignBits()
{
  finish();
  m_pcTComBitIf->write(1, 1);
  m_pcTComBitIf->writeAlignZero(); // pcm align zero
}

/** Write a PCM code.
 * \param uiCode code value
 * \param uiLength code bit-depth
 * \returns Void
 */
Void TEncBinCABAC::xWritePCMCode(UInt uiCode, UInt uiLength)
{
  m_pcTComBitIf->write(uiCode, uiLength);
}

Void TEncBinCABAC::copyState( const TEncBinIf* pcTEncBinIf )
{
  const TEncBinCABAC* pcTEncBinCABAC = pcTEncBinIf->getTEncBinCABAC();
  m_uiLow           = pcTEncBinCABAC->m_uiLow;
  m_uiRange         = pcTEncBinCABAC->m_uiRange;
  m_bitsLeft        = pcTEncBinCABAC->m_bitsLeft;
  m_bufferedByte    = pcTEncBinCABAC->m_bufferedByte;
  m_numBufferedBytes = pcTEncBinCABAC->m_numBufferedBytes;
#if FAST_BIT_EST
  m_fracBits = pcTEncBinCABAC->m_fracBits;
#endif
}

Void TEncBinCABAC::resetBits()
{
  m_uiLow            = 0;
  m_bitsLeft         = 23;
  m_numBufferedBytes = 0;
  m_bufferedByte     = 0xff;
  if ( m_binCountIncrement )
  {
    m_uiBinsCoded = 0;
  }
#if FAST_BIT_EST
  m_fracBits &= 32767;
#endif
}

UInt TEncBinCABAC::getNumWrittenBits()
{
  return m_pcTComBitIf->getNumberOfWrittenBits() + 8 * m_numBufferedBytes + 23 - m_bitsLeft;
}

/**
 * \brief Encode bin
 *
 * \param binValue   bin value
 * \param rcCtxModel context model
 */
Void TEncBinCABAC::encodeBin( UInt binValue, ContextModel &rcCtxModel )
{
  //{
  //  DTRACE_CABAC_VL( g_nSymbolCounter++ )
  //  DTRACE_CABAC_T( "\tstate=" )
  //  DTRACE_CABAC_V( ( rcCtxModel.getState() << 1 ) + rcCtxModel.getMps() )
  //  DTRACE_CABAC_T( "\tsymbol=" )
  //  DTRACE_CABAC_V( binValue )
  //  DTRACE_CABAC_T( "\n" )
  //}

#ifdef DEBUG_CABAC_BINS
  const UInt startingRange = m_uiRange;
#endif

  m_uiBinsCoded += m_binCountIncrement;
  rcCtxModel.setBinsCoded( 1 );

  UInt  uiLPS   = TComCABACTables::sm_aucLPSTable[ rcCtxModel.getState() ][ ( m_uiRange >> 6 ) & 3 ];
  m_uiRange    -= uiLPS;

  if( binValue != rcCtxModel.getMps() )
  {
    Int numBits = TComCABACTables::sm_aucRenormTable[ uiLPS >> 3 ];
    m_uiLow     = ( m_uiLow + m_uiRange ) << numBits;
    m_uiRange   = uiLPS << numBits;
    rcCtxModel.updateLPS();
    m_bitsLeft -= numBits;
    testAndWriteOut();
  }
  else
  {
    rcCtxModel.updateMPS();

    if ( m_uiRange < 256 )
    {
      m_uiLow <<= 1;
      m_uiRange <<= 1;
      m_bitsLeft--;
      testAndWriteOut();
    }
  }

#ifdef DEBUG_CABAC_BINS
  if ((g_debugCounter + debugCabacBinWindow) >= debugCabacBinTargetLine)
    std::cout << g_debugCounter << ": coding bin value " << binValue << ", range = [" << startingRange << "->" << m_uiRange << "]\n";

  if (g_debugCounter >= debugCabacBinTargetLine)
  {
    Char breakPointThis;
    breakPointThis = 7;
  }
  if (g_debugCounter >= (debugCabacBinTargetLine + debugCabacBinWindow)) exit(0);
  g_debugCounter++;
#endif
}

/**
 * \brief Encode equiprobable bin
 *
 * \param binValue bin value
 */
Void TEncBinCABAC::encodeBinEP( UInt binValue )
{
  if (false)
  {
    DTRACE_CABAC_VL( g_nSymbolCounter++ )
    DTRACE_CABAC_T( "\tEPsymbol=" )
    DTRACE_CABAC_V( binValue )
    DTRACE_CABAC_T( "\n" )
  }

  m_uiBinsCoded += m_binCountIncrement;

  if (m_uiRange == 256)
  {
    encodeAlignedBinsEP(binValue, 1);
    return;
  }

  m_uiLow <<= 1;
  if( binValue )
  {
    m_uiLow += m_uiRange;
  }
  m_bitsLeft--;

  testAndWriteOut();
}

/**
 * \brief Encode equiprobable bins
 *
 * \param binValues bin values
 * \param numBins number of bins
 */
Void TEncBinCABAC::encodeBinsEP( UInt binValues, Int numBins )
{
  m_uiBinsCoded += numBins & -m_binCountIncrement;

  if (false)
  {
    for ( Int i = 0; i < numBins; i++ )
    {
      DTRACE_CABAC_VL( g_nSymbolCounter++ )
      DTRACE_CABAC_T( "\tEPsymbol=" )
      DTRACE_CABAC_V( ( binValues >> ( numBins - 1 - i ) ) & 1 )
      DTRACE_CABAC_T( "\n" )
    }
  }

  if (m_uiRange == 256)
  {
    encodeAlignedBinsEP(binValues, numBins);
    return;
  }

  while ( numBins > 8 )
  {
    numBins -= 8;
    UInt pattern = binValues >> numBins;
    m_uiLow <<= 8;
    m_uiLow += m_uiRange * pattern;
    binValues -= pattern << numBins;
    m_bitsLeft -= 8;

    testAndWriteOut();
  }

  m_uiLow <<= numBins;
  m_uiLow += m_uiRange * binValues;
  m_bitsLeft -= numBins;

  testAndWriteOut();
}

Void TEncBinCABAC::align()
{
  m_uiRange = 256;
}

Void TEncBinCABAC::encodeAlignedBinsEP( UInt binValues, Int numBins )
{
  Int binsRemaining = numBins;

  assert(m_uiRange == 256); //aligned encode only works when range = 256

  while (binsRemaining > 0)
  {
    const UInt binsToCode = std::min<UInt>(binsRemaining, 8); //code bytes if able to take advantage of the system's byte-write function
    const UInt binMask    = (1 << binsToCode) - 1;

    const UInt newBins = (binValues >> (binsRemaining - binsToCode)) & binMask;

    //The process of encoding an EP bin is the same as that of coding a normal
    //bin where the symbol ranges for 1 and 0 are both half the range:
    //
    //  low = (low + range/2) << 1       (to encode a 1)
    //  low =  low            << 1       (to encode a 0)
    //
    //  i.e.
    //  low = (low + (bin * range/2)) << 1
    //
    //  which is equivalent to:
    //
    //  low = (low << 1) + (bin * range)
    //
    //  this can be generalised for multiple bins, producing the following expression:
    //
    m_uiLow = (m_uiLow << binsToCode) + (newBins << 8); //range is known to be 256

    binsRemaining -= binsToCode;
    m_bitsLeft    -= binsToCode;

    testAndWriteOut();
  }
}

/**
 * \brief Encode terminating bin
 *
 * \param binValue bin value
 */
Void TEncBinCABAC::encodeBinTrm( UInt binValue )
{
  m_uiBinsCoded += m_binCountIncrement;
  m_uiRange -= 2;
  if( binValue )
  {
    m_uiLow  += m_uiRange;
    m_uiLow <<= 7;
    m_uiRange = 2 << 7;
    m_bitsLeft -= 7;
  }
  else if ( m_uiRange >= 256 )
  {
    return;
  }
  else
  {
    m_uiLow   <<= 1;
    m_uiRange <<= 1;
    m_bitsLeft--;
  }

  testAndWriteOut();
}

Void TEncBinCABAC::testAndWriteOut()
{
  if ( m_bitsLeft < 12 )
  {
    writeOut();
  }
}

/**
 * \brief Move bits from register into bitstream
 */
Void TEncBinCABAC::writeOut()
{
  UInt leadByte = m_uiLow >> (24 - m_bitsLeft);
  m_bitsLeft += 8;
  m_uiLow &= 0xffffffffu >> m_bitsLeft;

  if ( leadByte == 0xff )
  {
    m_numBufferedBytes++;
  }
  else
  {
    if ( m_numBufferedBytes > 0 )
    {
      UInt carry = leadByte >> 8;
      UInt byte = m_bufferedByte + carry;
      m_bufferedByte = leadByte & 0xff;
      m_pcTComBitIf->write( byte, 8 );

      byte = ( 0xff + carry ) & 0xff;
      while ( m_numBufferedBytes > 1 )
      {
        m_pcTComBitIf->write( byte, 8 );
        m_numBufferedBytes--;
      }
    }
    else
    {
      m_numBufferedBytes = 1;
      m_bufferedByte = leadByte;
    }
  }
}

//! \}