id	summary	reporter	owner	description	type	status	priority	milestone	component	version	resolution	keywords	cc
1435	Mismatch on ScalingMatrixRec derivation in eq.(105) between Spec and SW	tsukuba.takeshi		"In the spec (JVET-S2001vH), ScalingMatrixRec derivation is defined as in eq. (105):

ScalingMatrixRec[ id ][ x ][ y ] = ( ScalingMatrixPred[ x ][ y ] + ScalingList[ id ][ k ] ) & 255	(105)
	with k = 0..( matrixSize * matrixSize − 1 ),
		x = DiagScanOrder[ Log2( matrixSize ) ][ Log2( matrixSize ) ][ k ][ 0 ], and
		y = DiagScanOrder[ Log2( matrixSize ) ][ Log2( matrixSize ) ][ k ][ 1 ]

However, in VTM-10.2, ScalingMatrixRec derivation is implemented as below:

{{{
VLCReader.cpp void HLSSyntaxReader::decodeScalingList(...)
{
... 
  for(i = 0; i < coefNum; i++)
  {
    ...
    READ_SVLC( data, ""scaling_list_delta_coef"");
    nextCoef += data;
    predCoef = (isPredictor) ? srcPred[scan[i].idx] : 0;
    dst[scan[i].idx] = (nextCoef + predCoef + 256) & 255;
  }
...
}
}}}
, where the parameter nextCoef, predCoef and dst[scan[i].idx] in code are corresponding to ScalingList[id][k], ScalingMatrixPred[x][y], and ScalingMatrixRec[id][x][y] in the spec.

As can be seen, there is ""+256"" in SW but not in Spec.


Looking at the adopt text JVET-P1034, ""+256"" is found in the syntax table.

  ...
  scaling_list_delta_coef	se(v)
  nextCoef = ( nextCoef + scaling_list_delta_coef '''+ 256''' ) % 256	
  ScalingList[ scalingListId ][ i ] = nextCoef	
  ...

Or looking at JVET-P2001vC, ""+256"" is found in ScalingMatrixRec derivation as below. 

ScalingMatrixRec[ id ][ x ][ y ] = ( ScalingMatrixPred[ x ][ y ] + ScalingList[ id ][ k ]  '''+ 256''' ) % & 256 )	(7 72)
	with k = 0..( matrixSize * matrixSize − 1 ),
		x = DiagScanOrder[ Log2( matrixSize ) ][ Log2( matrixSize ) ][ k ][ 0 ], and
		y = DiagScanOrder[ Log2( matrixSize ) ][ Log2( matrixSize ) ][ k ][ 1 ]


But text clean-up after JVET-P2001vD, ""+256"" was deleted.

Suggested fix is to align Spec to SW.

ScalingMatrixRec[ id ][ x ][ y ] = ( ScalingMatrixPred[ x ][ y ] + ScalingList[ id ][ k ] + '''256''') & 255	(105)
	with k = 0..( matrixSize * matrixSize − 1 ),
		x = DiagScanOrder[ Log2( matrixSize ) ][ Log2( matrixSize ) ][ k ][ 0 ], and
		y = DiagScanOrder[ Log2( matrixSize ) ][ Log2( matrixSize ) ][ k ][ 1 ]

"	defect	closed	minor		spec	VVC D10 vH	invalid		ksuehring bbross XiangLi fbossen jvet@…