le qo is greater than or equal to 4 in units of quarter luma frame samples or the absolute difference between the horizontal or vertical components of the list 1 motion vector used in the prediction of the macroblock/sub-macroblock partition containing the sample Po and list 0 motion vector used in the prediction of the macroblock/sub-macroblock partition containing the sample qo is greater than or equal to 4 in units of quarter luma frame samples. NOTE 3 - A vertical difference of 4 in units of quarter luma frame samples is a difference of 2 in units of quarter luma field samples. Otherwise, a value of bS equal to 0 is the output. 8.7.2.2 Derivation process for the thresholds for each block edge Inputs to this process are: the input sample values Po, qo, p1 and q1 of a single set of samples across an edge that is to be filtered, the variables chromaEdgeFlag and bS, for the set of input samples, as specified in clause 8.7.2, the variables filterOffsetA, filterOffsetB, qPp, and qPq. Outputs of this process are the variable filterSamplesFlag, which indicates whether the input samples are filtered, the value of indexA, and the values of the threshold variables a and B. Let qPav be a variable specifying an average quantisation parameter. It is derived as: qPav =(qP,+qPq+1)>> (8-453) NOTE - In SP and SI slices, qPav is derived in the same way as in other slice types. QSy from Equation 7-30 is not used in the deblocking filter. Let indexA be a variable that is used to access the a table (Table 8-16) as well as the tco table (Table 8-17), which is used in filtering of edges with bS less than 4 as specified in clause 8.7.2.3, and let indexB be a variable that is used to access the table (Table 8-16). The variables indexA and indexB are derived as: indexA = Clip3( 0, 51, qPav filterOffsetA ) (8-454) indexB = Clip3( 0, 51, qPav + filterOffsetB (8-455) The variables a' and ' depending on the values of indexA and indexB are specified in Table 8-16. Depending on chromaEdgeFlag, the corresponding threshold variables a and are 