id	summary	reporter	owner	description	type	status	priority	milestone	component	version	resolution	keywords	cc
67	Implicit vertical BT split at picture boundary issue	bbross		"Consider the following case:

If a CU:
- crosses the right boundary of the picture and
- has cbSize size is greater than MinQtSizeY and smaller than or equal to MaxBtSizeY
then
- qt_split_cu_flag is signalled

If qt_split_cu_flag is signalled as 0 (no QT split)
- multi_type_tree is called and 
- allowSplitBtHor, allowSplitTtVer and allowSplitTtHor=false but allowSplitBtVer=true
then
- '''mtt_split_cu_flag is signalled although it should be inferred to be equal to 1'''

A simple fix would 
1. add the following condition to the signalling of mtt_split_cu_flag:
- if( ( allowSplitBtVer  | |  allowSplitBtHor  | |  allowSplitTtVer  | |  allowSplitTtHor ) ''' &&  ( x0 + cbWidth  <=  pic_width_in_luma_samples )  &&  ( y0 + cbHeight  <=  pic_height_in_luma_samples )'''  )
2. infer its value in case it is not present as:
* If one or more of the following conditions are true, the value of mtt_split_cu_flag is inferred to be equal to 1. 
  * x0 + cbWidth is greater than pic_width_in_luma_samples.
  * y0 + cbHeight is greater than pic_height_in_luma_samples.
* Otherwise, the value of mtt_split_cu_vertical_flag is inferred to be equal to 0.

Thanks Virginie for spotting this."	defect	closed	minor	VVC D2 v2	spec	VVC D2 v1	fixed		ksuehring bbross XiangLi fbossen jvet@…