id	summary	reporter	owner	description	type	status	priority	milestone	component	version	resolution	keywords	cc
397	Mismatch with vtm on CclmEnabled derivation	forayr		"The issue happens on a CU 64x64 split using SPLIT_TT_HOR mode, and gives 3 Cb (64x16, 64x32 and 64x16).

The specification indicate for the CclmEnabled dirivation:
{{{
 - If one of the following conditions is true, the variable CclmEnabled is set equal to 1:
    - CbWidth[ 1 ][ xCb64 ][ yCb64 ] is equal to 64 and CbHeight[ 1 ][ xCb64 ][ yCb64 ] is equal to 64.
    - CbWidth[ 1 ][ xCb64 ][ yCb32 ] is equal to 64 and CbHeight[ 1 ][ xCb64 ][ yCb32 ] is equal to 32
    - CqtDepth[ 1 ][ xCb64 ][ yCb64 ] is greater than CtbLog2SizeY − 6.
    - CqtDepth[ 1 ][ xCb64 ][ yCb64 ] is equal to CtbLog2SizeY − 6, MttSplitMode[ xCb64 ][ yCb64 ][ 0 ] is equal to SPLIT_BT_HOR, and MttSplitMode[ xCb64 ][ yCb32 ][ 1 ] is equal to SPLIT_BT_VER.
 - Otherwise, the variable CclmEnabled is set equal to 0.
}}}
For the 3rd Cb, we have:
 - xCb = 0, yCb = 48
 - xCb64 = 0, yCb64 = 0, yCb32 = 32.
 - CbWidth[ 1 ][ xCb64 ][ yCb32 ] = 64 
 - CbHeight[ 1 ][ xCb64 ][ yCb32 ] = 32 (this is the size of the 2nd Cb)
Therefore CclmEnabled might be equal to 1 as this fulfilled the 2nd condition.

However in the vtm, this condition corresponds to
{{{
int depthFor64x64Node = slice->getSPS()->getCTUSize() == 128 ? 1 : 0;
const PartSplit cuSplitTypeDepth1 = CU::getSplitAtDepth( *this, depthFor64x64Node );
const PartSplit cuSplitTypeDepth2 = CU::getSplitAtDepth( *this, depthFor64x64Node + 1 );
...
//allow CCLM if 64x32 chroma tree node uses NS and becomes a chroma CU containing 32x16 chroma blocks
else if( cuSplitTypeDepth1 == CU_HORZ_SPLIT && cuSplitTypeDepth2 == CU_DONT_SPLIT )
{
   CHECK( !(blocks[COMPONENT_Cb].width == 32 && blocks[COMPONENT_Cb].height == 16), ""chroma cu size shall be 32x16"" );
   allowCCLM = true;
}
}}}
As cuSplitTypeDepth1 = CU_TRIH_SPLIT, the condition is not true and CclmEnabled is equal to 0."	defect	closed	minor	VVC D6 vE	spec		fixed		ksuehring bbross XiangLi fbossen jvet@…