id	summary	reporter	owner	description	type	status	priority	milestone	component	version	resolution	keywords	cc
373	JVET-O0590 with DMVR SAD Doubled	bheng		"The SAD value returned from xDMVRCost( ) appears to be doubled relative to what is specified in the draft text, Section 8.5.3.3.  

Specifically, see function xGetSAD_NxN_SIMD() where the SAD is doubled at the following line:

    uiSum <<= iSubShift;

With care about various thresholds, this can be made to be equivalent to what is specified in the draft text.

However, for JVET-O0590, with a doubled SAD value, the following operation has a different level of precision so the results can be different (off by 1 point).  

    minCost -= (minCost >>2);

This can lead to different DMVR search results.

This specific issue could be solved by adjusting the precision before/after the right shift above.  
    
    minCost >>= 1;
    minCost -= (minCost >>2);            
    minCost <<= 1;

But it would probably be better just to change xDMVRCost to match the spec and adjust all the thresholds accordingly.


"	defect	closed	minor	VTM-6.0	VTM	VTM-5.2	fixed		ksuehring XiangLi fbossen jvet@…