According to Table 9-38, skip_flag uses left and above skip_flag to derive the context index for CABAC decoding. However, instead of storing the neighboring skip_flag, the current HM 7.0 uses the following condition to determine the value of the neighboring skip_flag

 if ( m_pcSlice->isIntra () )
  {
    return false;
  }
  return ( getMergeFlag( uiPartIdx ) && getPartitionSize( uiPartIdx ) == SIZE_2Nx2N && !getQtRootCbf( uiPartIdx ) );

On the other hand, the new cbf flag coding rules in HM 7.0 allows the top layer chroma cbf to be one while all child chroma cbf flags to be zero. Although the example may be useless for a smart encoder, if allowed, it will make the above mentioned condition no longer equivalent to skip_flag equal to one and hence cause inconsistency between HM and spec.

Suggested fix may be either fix the spec to disallow such cases or fix the HM to use the real neighboring skip_flag value to derive the context.

This bug occurs when the active pps id is not equal to zero.

The current HM reference decoder always assumes that the active PPS id is equal to zero and will crash if it is not.

Bool TDecTop::xDecodeSlice(...)
{
  ...
  //!!!KS: DIRTY HACK
  m_apcSlicePilot->setPPSId(0);
  m_apcSlicePilot->setPPS(m_parameterSetManagerDecoder.getPrefetchedPPS(0));

This bug occurs when there are different PPSs using the same pic_parameter_set_id value.

The current HM decoder conducts the deblocking and ALF process when a slice of a new picture is detected. So if a different PPS using the same pic_parameter_set_id precedes that new slice, the PPS content of the current picture will be overridden and the deblocking process of the current picture will hence use the incorrect PPS info.

  bNewPicture = m_cTDecTop.decode(nalu, m_iSkipFrame, m_iPOCLastDisplay);
  
  if (bNewPicture)
  {
    bitstreamFile.clear();
    bitstreamFile.seekg(location-streamoff(3));
    bytestream.reset();
  }
  bPreviousPictureDecoded = true; 
 
  if (bNewPicture || !bitstreamFile)
  {
    m_cTDecTop.executeDeblockAndAlf(uiPOC, pcListPic, m_iSkipFrame, m_iPOCLastDisplay);
  }