id	summary	reporter	owner	description	type	status	priority	milestone	component	version	resolution	keywords	cc
1379	Undefined behaviour when pps_rpl1_idx_present_flag == 0, and sps_num_ref_pic_lists[0] > sps_num_ref_pic_lists[1]	forayr		"In rpl_sps[i] semantics, the following inference rules are present:

When rpl_sps_flag[i] is equal to 1 and sps_num_ref_pic_lists[i] is equal to 1, the value of rpl_idx[i] is inferred to be equal to 0.
When rpl_sps_flag[i] is equal to 1 and pps_rpl1_idx_present_flag is equal to 0, the value of rpl_idx[1] is inferred to be equal to rpl_idx[0].

In the second case (sps_num_ref_pic_lists[i] > 1), there is no check that rpl_idx[1] (inferred to rpl_idx[0]) is less then sps_num_ref_pic_lists[1], and we might use an undefined RPL if sps_num_ref_pic_lists[1] > sps_num_ref_pic_lists[0].

I think that the following constraint should be added in rpl_idx[i] semantics:
When pps_rpl1_idx_present_flag is equal to 0 and sps_num_ref_pic_lists[1] is not equal to 1, rpl_idx[i] should be less than min(sps_num_ref_pic_lists[0], 
sps_num_ref_pic_lists[1]).
"	defect	closed	minor		spec	VVC D10 vG	fixed		ksuehring bbross XiangLi fbossen jvet@…