Redundant condition on DBF maxFilterLength derivation

[abe.kiyo]

In 8.8.3.4 Derivation process of coding subblock boundary, there is the following description.

– Otherwise, if one or more of the following conditions are true:

– ( x + 4 ) is greater than or equal to nCbW,
– edgeTbFlags[ x − 4 ][ y ] is equal to 1,
– edgeTbFlags[ x + 4 ][ y ] is equal to 1,

the following applies:

maxFilterLengthPs[ x ][ y ] = 1 (1253)
maxFilterLengthQs[ x ][ y ] = 1 (1254)

x is always 8 grid potion inside the current coding block. The coding block size of subblock mode is always a multiple of 8. Therefore, it will never meet the first condition. I suggest the first condition should be removed. It is same for horizontal edges.

[ZhipinDeng]

The condition "( y + 4 ) is greater than or equal to nCbH" for deblocking EDGE_HOR in section 8.8.3.4 is also redundant and should be deleted. Same reason, i.e., deblocking is applied at 8x8 grid for subblock boundaries thereby this condition would never hit.

[Kenneth]

That’s correct. Those checks are redundant. Same applies to VTM.

[bbross]

Will be fixed in JVET-S2001-vA.