Need clearification for 8.4.3 Derivation process for chroma intra prediction mode

[nuomi]

For 12b444vvc1_A_Sony_2.bit, the second decode frame(poc 32), and cu position (64,68)
The treeType is equal to SINGLE_TREE, sps_chroma_format_idc is equal to 3, intra_chroma_pred_mode is equal to 0,and IntraMipFlag[ xCb ][ yCb ] is equal to 1

based on

1. If IntraMipFlag[ xCb + cbWidth / 2 ][ yCb + cbHeight / 2 ] is equal to 1, lumaIntraPredMode is set equal toINTRA_PLANAR.
2. Table 20

we need set IntraPredModeC to 66, which conflicts with vtm code ​https://vcgit.hhi.fraunhofer.de/jvet/VVCSoftware_VTM/-/blob/master/source/Lib/CommonLib/UnitTools.cpp#L734

could you explain why?

thank you.

[bbross]

Thanks for reporting and this is related to #1558 fixing another bug in the mode derivation for 444.
Indeed, the VTM behaviour for 444 is correct and the attached fix based on the JVET-AD2005 text fixes the issue.

[bbross]

To be fixed as suggested in both the ITU-T and ISO texts for VVC v3.

[nuomi]

thank you bbross