id summary reporter owner description type status priority milestone component version resolution keywords cc 1140 Mismatch between spec and VTM about context modeling for intra_luma_not_planar_flag Jun_bd " ''Problem statement:'' In spec S2001-v1 (Table 131 – Assignment of ctxInc to syntax elements with context coded bins), the ctxInc for syntax element intra_luma_not_planar_flag (only one bin) is specified as [[span(style=color: #FF0000, intra_subpartitions_mode_flag )]], which means '''if ""intra_subpartitions_mode_flag"" is 1 (ISP mode), ctxInc is 1''' and '''if ""intra_subpartitions_mode_flag"" is 0 (non-ISP) ctxInc is 0'''. However, in the latest VTM (commit id: cb7b243e), the ctxInc for intra_luma_not_planar_flag is computed in the other way around (shown below, 1384 line of CABACReader.cpp). {{{ unsigned ctx = (pu->cu->ispMode == NOT_INTRA_SUBPARTITIONS ? 1 : 0); }}} It can be seen that '''if current CU uses ISP mode''' (pu->cu->ispMode == NOT_INTRA_SUBPARTITIONS is FALSE), '''the ctxInc is 0''' and '''if current CU uses non-ISP mode''' (pu->cu->ispMode == NOT_INTRA_SUBPARTITIONS is TRUE), '''the ctxInc is 1'''. ''Suggestion'': Aligning spec with SW, i.e., specify the ctxInc for intra_luma_not_planar_flag as [[span(style=color: #FF0000, !intra_subpartitions_mode_flag )]] in spec." defect closed minor spec VVC D9 vB fixed intra_luma_not_planar_flag, mismatch ksuehring bbross XiangLi fbossen jvet@…