NALread.cpp

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/**
 \file     NALread.cpp
 \brief    reading functionality for NAL units
 */


#include <vector>
#include <algorithm>
#include <ostream>

#include "NALread.h"

#include "CommonLib/NAL.h"
#include "CommonLib/BitStream.h"
#include "CommonLib/Rom.h"
#include "CommonLib/dtrace_next.h"

#if RExt__DECODER_DEBUG_BIT_STATISTICS
#include "CommonLib/CodingStatistics.h"
#endif

//! \ingroup DecoderLib
//! \{
static void convertPayloadToRBSP(std::vector<uint8_t> &nalUnitBuf, InputBitstream *bitstream, bool isVclNalUnit)
{
  uint32_t zeroCount = 0;
  std::vector<uint8_t>::iterator it_read, it_write;

  uint32_t pos = 0;
  bitstream->clearEmulationPreventionByteLocation();
  for (it_read = it_write = nalUnitBuf.begin(); it_read != nalUnitBuf.end(); it_read++, it_write++, pos++)
  {
    CHECK(zeroCount >= 2 && *it_read < 0x03, "Zero count is '2' and read value is small than '3'");
    if (zeroCount == 2 && *it_read == 0x03)
    {
      bitstream->pushEmulationPreventionByteLocation( pos );
      pos++;
      it_read++;
      zeroCount = 0;
#if RExt__DECODER_DEBUG_BIT_STATISTICS
      CodingStatistics::IncrementStatisticEP(STATS__EMULATION_PREVENTION_3_BYTES, 8, 0);
#endif
      if (it_read == nalUnitBuf.end())
      {
        break;
      }
      CHECK(*it_read > 0x03, "Read a value bigger than '3'");
    }
    zeroCount = (*it_read == 0x00) ? zeroCount+1 : 0;
    *it_write = *it_read;
  }
  CHECK(zeroCount != 0, "Zero count not '0'");

  if (isVclNalUnit)
  {
    // Remove cabac_zero_word from payload if present
    int n = 0;

    while (it_write[-1] == 0x00)
    {
      it_write--;
      n++;
    }

    if (n > 0)
    {
      msg( NOTICE, "\nDetected %d instances of cabac_zero_word\n", n/2);
    }
  }

  nalUnitBuf.resize(it_write - nalUnitBuf.begin());
}

#if ENABLE_TRACING
static void xTraceNalUnitHeader(InputNALUnit& nalu)
{
  DTRACE( g_trace_ctx, D_NALUNITHEADER, "*********** NAL UNIT (%s) ***********\n", nalUnitTypeToString(nalu.m_nalUnitType) );
  bool zeroTidRequiredFlag = 0;
  if ((nalu.m_nalUnitType >= 16) && (nalu.m_nalUnitType <= 31))
  {
    zeroTidRequiredFlag = 1;
  }
  DTRACE( g_trace_ctx, D_NALUNITHEADER, "%-50s u(%d)  : %u\n", "zero_tid_required_flag", 1, zeroTidRequiredFlag );
  DTRACE( g_trace_ctx, D_NALUNITHEADER, "%-50s u(%d)  : %u\n", "nuh_temporal_id_plus1", 3, nalu.m_temporalId + 1 );
  DTRACE( g_trace_ctx, D_NALUNITHEADER, "%-50s u(%d)  : %u\n", "nal_unit_type_lsb", 4, (nalu.m_nalUnitType) - (zeroTidRequiredFlag << 4));
  DTRACE( g_trace_ctx, D_NALUNITHEADER, "%-50s u(%d)  : %u\n", "nuh_layer_id_plus1", 7, nalu.m_nuhLayerId+1);
  DTRACE( g_trace_ctx, D_NALUNITHEADER, "%-50s u(%d)  : %u\n", "nuh_reserved_zero_bit", 1, 0 );
}
#endif

void readNalUnitHeader(InputNALUnit& nalu)
{
  InputBitstream& bs = nalu.getBitstream();

  nalu.m_forbiddenZeroBit   = bs.read(1);                 // forbidden zero bit
  nalu.m_nuhReservedZeroBit = bs.read(1);                 // nuh_reserved_zero_bit
  nalu.m_nuhLayerId         = bs.read(6);                 // nuh_layer_id
  CHECK(nalu.m_nuhLayerId > 55, "The value of nuh_layer_id shall be in the range of 0 to 55, inclusive");
  nalu.m_nalUnitType        = (NalUnitType) bs.read(5);   // nal_unit_type
  nalu.m_temporalId         = bs.read(3) - 1;             // nuh_temporal_id_plus1

#if RExt__DECODER_DEBUG_BIT_STATISTICS
  CodingStatistics::IncrementStatisticEP(STATS__NAL_UNIT_HEADER_BITS, 1+3+4+7+1, 0);
#endif

#if ENABLE_TRACING
  xTraceNalUnitHeader(nalu);
#endif

  // only check these rules for base layer
  if (nalu.m_nuhLayerId == 0)
  {
    if ( nalu.m_temporalId )
    {
    }
    else
    {
      CHECK(nalu.m_nalUnitType == NAL_UNIT_CODED_SLICE_STSA
        , "When NAL unit type is equal to STSA_NUT, TemporalId shall not be equal to 0");
    }
  }
}
/**
 * create a NALunit structure with given header values and storage for
 * a bitstream
 */
void read(InputNALUnit& nalu)
{
  InputBitstream &bitstream = nalu.getBitstream();
  std::vector<uint8_t> &nalUnitBuf = bitstream.getFifo();
  // perform anti-emulation prevention
  const NalUnitType nut = (NalUnitType)(nalUnitBuf[1] >> 3);
  convertPayloadToRBSP(nalUnitBuf, &bitstream, nut <= NAL_UNIT_RESERVED_IRAP_VCL_11);
  bitstream.resetToStart();
  readNalUnitHeader(nalu);
}

bool checkPictureHeaderInSliceHeaderFlag(InputNALUnit& nalu)
{
  InputBitstream& bitstream = nalu.getBitstream();
  CHECK(bitstream.getByteLocation() != 2, "The picture_header_in_slice_header_flag is the first bit after the NAL unit header");
  return (bool)bitstream.read(1);
}
//! \}