id	summary	reporter	owner	description	type	status	priority	milestone	component	version	resolution	keywords	cc
500	Redundant cbf_cb and cbf_cr flags when log2MaxTrafoSize is set to two	zhyang123	bbross	"Similar to the previous HM ticket #312, the working draft also has the issue that when log2MaxTrafoSize is two, there are three redundant cbf_cb and cbf_cr flags for each 4x4 chroma TU. 

In section 7.3.8 transform tree syntax, firstChromaCbf is derived as follows:

{{{ 
firstChromaCbf = ( log2TrafoSize = = Log2MaxTrafoSize | | trafoDepth = = 0 ) ? 1 : 0
}}}

The above formula does not consider the case when log2MaxTrafoSize is two. In that case,  bFirstCbfOfCU is always true for each 4x4 luma TU, which in turn causes a set of cbf_cb and cbf_cr flags to be coded. Although only the 4th luma TU is associated with a chroma TU and should contain a set of coded cbf_cb and cbf_cr flags. 

A possible fix may be to replace the above formula by the following one
{{{
firstChromaCbf = ((log2TrafoSize == log2MaxTrafoSize && (log2TrafoSize > 2 || blkIdx == 3)) || trafoDepth == 0 )
}}}"	defect	closed	minor		Text	D6 (H1003) dI/dJ/dK	fixed		bbross wjhan jct-vc@…