HEVC代码追踪（十三）:解码之decode

// ====================================================================================================================
// Public member functions
// ====================================================================================================================

/**
 - create internal class
 - initialize internal class
 - until the end of the bitstream, call decoding function in TDecTop class
 - delete allocated buffers
 - destroy internal class
 .
 */
Void TAppDecTop::decode()
{
  Int                 poc;
  TComList<TComPic*>* pcListPic = NULL;

  ifstream bitstreamFile(m_pchBitstreamFile, ifstream::in | ifstream::binary);
  if (!bitstreamFile)
  {
    fprintf(stderr, "\nfailed to open bitstream file `%s' for reading\n", m_pchBitstreamFile);
    exit(EXIT_FAILURE);
  }

  InputByteStream bytestream(bitstreamFile);

  // create & initialize internal classes
  xCreateDecLib();
  xInitDecLib  ();
  m_iPOCLastDisplay += m_iSkipFrame;      // set the last displayed POC correctly for skip forward.

  // main decoder loop
  Bool openedReconFile = false; // reconstruction file not yet opened. (must be performed after SPS is seen)
  Bool loopFiltered = false;
  
  while (!!bitstreamFile)
  {
    /* location serves to work around a design fault in the decoder, whereby
     * the process of reading a new slice that is the first slice of a new frame
     * requires the TDecTop::decode() method to be called again with the same
     * nal unit. */
    streampos location = bitstreamFile.tellg();
    AnnexBStats stats = AnnexBStats();

    vector<uint8_t> nalUnit;
    InputNALUnit nalu;
    byteStreamNALUnit(bytestream, nalUnit, stats);

    // call actual decoding function
    Bool bNewPicture = false;
    if (nalUnit.empty())
    {
      /* this can happen if the following occur:
       *  - empty input file
       *  - two back-to-back start_code_prefixes
       *  - start_code_prefix immediately followed by EOF
       */
      fprintf(stderr, "Warning: Attempt to decode an empty NAL unit\n");
    }
    else
    {
      read(nalu, nalUnit);
      if( (m_iMaxTemporalLayer >= 0 && nalu.m_temporalId > m_iMaxTemporalLayer) || !isNaluWithinTargetDecLayerIdSet(&nalu)  )
      {
        bNewPicture = false;
      }
      else
      {
        bNewPicture = m_cTDecTop.decode(nalu, m_iSkipFrame, m_iPOCLastDisplay);
        if (bNewPicture)
        {
          bitstreamFile.clear();
          /* location points to the current nalunit payload[1] due to the
           * need for the annexB parser to read three extra bytes.
           * [1] except for the first NAL unit in the file
           *     (but bNewPicture doesn't happen then) */
          bitstreamFile.seekg(location-streamoff(3));
          bytestream.reset();
        }
      }
    }
    if (bNewPicture || !bitstreamFile || nalu.m_nalUnitType == NAL_UNIT_EOS)
    {
      if (!loopFiltered || bitstreamFile)
      {
        m_cTDecTop.executeLoopFilters(poc, pcListPic);
      }
      loopFiltered = (nalu.m_nalUnitType == NAL_UNIT_EOS);
    }
#if !FIX_WRITING_OUTPUT
#if SETTING_NO_OUT_PIC_PRIOR
    if (bNewPicture && m_cTDecTop.getIsNoOutputPriorPics())
    {
      m_cTDecTop.checkNoOutputPriorPics( pcListPic );
    }
#endif
#endif

    if( pcListPic )
    {
      if ( m_pchReconFile && !openedReconFile )
      {
        if (!m_outputBitDepthY) { m_outputBitDepthY = g_bitDepthY; }
        if (!m_outputBitDepthC) { m_outputBitDepthC = g_bitDepthC; }

        m_cTVideoIOYuvReconFile.open( m_pchReconFile, true, m_outputBitDepthY, m_outputBitDepthC, g_bitDepthY, g_bitDepthC ); // write mode
        openedReconFile = true;
      }
#if FIX_WRITING_OUTPUT
      // write reconstruction to file
      if( bNewPicture )
      {
        xWriteOutput( pcListPic, nalu.m_temporalId );
      }
#if SETTING_NO_OUT_PIC_PRIOR
      if ( (bNewPicture || nalu.m_nalUnitType == NAL_UNIT_CODED_SLICE_CRA) && m_cTDecTop.getNoOutputPriorPicsFlag() )
      {
        m_cTDecTop.checkNoOutputPriorPics( pcListPic );
        m_cTDecTop.setNoOutputPriorPicsFlag (false);
      }
#endif
#endif
      if ( bNewPicture &&
           (   nalu.m_nalUnitType == NAL_UNIT_CODED_SLICE_IDR_W_RADL
            || nalu.m_nalUnitType == NAL_UNIT_CODED_SLICE_IDR_N_LP
            || nalu.m_nalUnitType == NAL_UNIT_CODED_SLICE_BLA_N_LP
            || nalu.m_nalUnitType == NAL_UNIT_CODED_SLICE_BLA_W_RADL
            || nalu.m_nalUnitType == NAL_UNIT_CODED_SLICE_BLA_W_LP ) )
      {
        xFlushOutput( pcListPic );
      }
      if (nalu.m_nalUnitType == NAL_UNIT_EOS)
      {
#if FIX_OUTPUT_EOS
        xWriteOutput( pcListPic, nalu.m_temporalId );
#else
        xFlushOutput( pcListPic );
#endif
      }
      // write reconstruction to file -- for additional bumping as defined in C.5.2.3
#if FIX_WRITING_OUTPUT
      if(!bNewPicture && nalu.m_nalUnitType >= NAL_UNIT_CODED_SLICE_TRAIL_N && nalu.m_nalUnitType <= NAL_UNIT_RESERVED_VCL31)
#else
      if(bNewPicture)
#endif
      {
        xWriteOutput( pcListPic, nalu.m_temporalId );
      }
    }
  }
  
  xFlushOutput( pcListPic );
  // delete buffers
  m_cTDecTop.deletePicBuffer();
  
  // destroy internal classes
  xDestroyDecLib();
}