Mismatch on PTL signalling in VPS between VTM and VVC spec

[martin.m.pettersson]

In the spec (JVET-T2001-v2), the profile_tier_level is set for VPS in the following syntax lines in section 7.3.2.3:

for( i = 0; i <= vps_num_ptls_minus1; i++ )

profile_tier_level( vps_pt_present_flag[ i ], vps_ptl_max_tid[ i ] )

However, in VTM-11.0, the call to profile_tier_level for VPS is implemented as

VLCWriter.cpp
void HLSWriter::codeVPS(const VPS* pcVPS)
{
  ...
  for (int i = 0; i < pcVPS->getNumPtls(); i++)
  {
    codeProfileTierLevel(&pcVPS->getProfileTierLevel(i), pcVPS->getPtPresentFlag(i), pcVPS->getPtlMaxTemporalId(i) - 1);
  }
  ...
}

VLCReader.cpp
void HLSyntaxReader::parseVPS(VPS* pcVPS)
{
  ...
  for (int i = 0; i < pcVPS->getNumPtls(); i++)
  {
    parseProfileTierLevel(&ptls[i], pcVPS->getPtPresentFlag(i), pcVPS->getPtlMaxTemporalId(i) - 1);
  }
  ...
}

As can be seen, there is a "-1" in the code but not in the spec. The effect is that information for the sublayer with the second highest TemporalID is never signalled in VPS.

The VTM code should probably be:

VLCWriter.cpp
void HLSWriter::codeVPS(const VPS* pcVPS)
{
  ...
  for (int i = 0; i < pcVPS->getNumPtls(); i++)
  {
    codeProfileTierLevel(&pcVPS->getProfileTierLevel(i), pcVPS->getPtPresentFlag(i), pcVPS->getPtlMaxTemporalId(i));
  }
  ...
}

VLCReader.cpp
void HLSyntaxReader::parseVPS(VPS* pcVPS)
{
  ...
  for (int i = 0; i < pcVPS->getNumPtls(); i++)
  {
    parseProfileTierLevel(&ptls[i], pcVPS->getPtPresentFlag(i), pcVPS->getPtlMaxTemporalId(i));
  }
  ...
}

[ksuehring]

Fixed in

​https://vcgit.hhi.fraunhofer.de/jvet/VVCSoftware_VTM/-/merge_requests/1974