id	summary	reporter	owner	description	type	status	priority	milestone	component	version	resolution	keywords	cc
1306	ScalingFactor for chroma 32x32 mismatch with reference code	peterderivaz		"In Q1005_v9 equation 7-48 is:

    ScalingFactor[ 3 ][ matrixId ][ x * 2 + k ][ y * 2 + j ] = ScalingFactor[ 2 ][ matrixId ][ x ][ y ] with x, y = 0..15, j = 0..1, k = 0..1

This means that the scaling factors for size 3 are constructed from  the scaling factors for size 2 in such a way that 

    ScalingFactor[ 3 ][ matrixId ][ 0 ][ 0 ] = ScalingFactor[ 2 ][ matrixId ][ 0 ][ 0 ]
    ScalingFactor[ 3 ][ matrixId ][ 0 ][ 1 ] = ScalingFactor[ 2 ][ matrixId ][ 0 ][ 0 ]
    ScalingFactor[ 3 ][ matrixId ][ 1 ][ 0 ] = ScalingFactor[ 2 ][ matrixId ][ 0 ][ 0 ]
    ScalingFactor[ 3 ][ matrixId ][ 1 ][ 1 ] = ScalingFactor[ 2 ][ matrixId ][ 0 ][ 0 ] 

However, the reference code does not appear to behave in this way.  In the reference code the DC value (ScalingFactor[ 3 ][ matrixId ][ 0 ][ 0 ]) can have a different value to the other 3.

I think the confusion may arise from the way ScalingFactor[ 2 ] is constructed.  ScalingFactor[ 2 ][matrixId][ 0 ][ 0 ] is defined both by equation 7-44 and by equation 7-45.

The reference code appears to behave in the following way:

1. Apply equation 7-44 to compute AC scaling values for size 2
2. Apply equation 7-48 to replicate the AC scaling values to size 3
3. Apply equation 7-45 to override the DC scaling value for size 2
4. Copy the new DC scaling value for size 2 to the DC scaling value for size 3


"	defect	closed	major	HM-15.0	RExt text	RExt D7 (Q1005) v8	fixed		davidf joel teruhiko jct-vc@…