id	summary	reporter	owner	description	type	status	priority	milestone	component	version	resolution	keywords	cc
802	Incomplete range of MaxNumTriangleMergeCand	XiangLi		"It was decided in N meeting to integrate JVET-N0447/JVET-N0400/JVET-N0500/JVET-N0851 on align triangle merge candidate number and regular merge candidate number. However, the range of MaxNumTriangleMergeCand was not correctly integrated into the spec. 

In JVET-N0851-v2 wd (uploaded 2019-03-24 11:01:44), we have 

max_num_merge_cand_minus_max_num_triangle_cand specifies the maximum number of triangular merge mode candidates supported in the tile group subtracted from MaxNumMergeCand. The maximum number of triangular merge mode candidates, MaxNumTriangleMergeCand is derived as follows:
MaxNumTriangleMergeCand = MaxNumMergeCand − max_num_merge_cand_minus_max_num_triangle_cand
'''The value of MaxNumTriangleMergeCand shall be in the range of 0, and 2 to MaxNumMergeCand, inclusive.''' When max_num_merge_cand_minus_max_num_triangle_cand is not signaled, MaxNumTriangleMergeCand is infered as 0. When MaxNumTriangleMergeCand is 0, no triangle merge mode is allowed for the current tile group. 

In spec integration, JVET-N1001-v3 (2019-04-30 16:20:58), we have

max_num_merge_cand_minus_max_num_triangle_cand specifies the maximum number of triangular merge mode candidates supported in the slice subtracted from MaxNumMergeCand. The maximum number of triangular merge mode candidates, MaxNumTriangleMergeCand is derived as follows:
MaxNumTriangleMergeCand = 
	MaxNumMergeCand − max_num_merge_cand_minus_max_num_triangle_cand	(7 60) 
When max_num_merge_cand_minus_max_num_triangle_cand is present, the value of '''MaxNumTriangleMergeCand shall be in the range of 2 to MaxNumMergeCand''', inclusive. When max_num_merge_cand_minus_max_num_triangle_cand is not present, MaxNumTriangleMergeCand is set equal to 0. When MaxNumTriangleMergeCand is equal to 0, no triangle merge mode is not allowed for the current slice.

It can be observed that it was proposed that the value of MaxNumTriangleMergeCand shall be in the range of 0, and 2 to MaxNumMergeCand, inclusive. Unfortunately, 0 was missing in the spec. Without 0, Triangle/GEO merge cannot be switched off by setting 0 candidates at slice level, which is not preferred. The bug should be fixed. The software was implemented as proposed in JVET-N0851.
"	defect	closed	minor		spec	VVC D7 vE	fixed		ksuehring bbross XiangLi fbossen jvet@…