I'm doing research on block noise caused by video compression (especially in newer codecs) and I've read the IEEE article about the HEVC deblocking filter (here).
However, when reading the algorithm I'm confused because the formula seems wrong. The first formula to determine if the deblocking filter will affect a block is:
$ |p_2,_0 - 2p_1,_0+p_0,_0|+|p_2,_3 - 2p_1,_3+p_0,_3|+|q_2,_0 - 2q_1,_0+q_0,_0|+|q_2,_3 - 2q_1,_3+q_0,_3|>\beta \ (1)$
It is also written (and shown in a figure) that $\beta $ increases with the quantification parameter QP.
Moreover, later it is written that to choose between normal and strong deblocking, the following equation is used (with $i$ going from $0$ to $3$):
$ |p_2,_i - 2p_1,_i+p_0,_i|+|q_2,_i - 2q_1,_i+q_0,_i|<\beta/8 \ (2) $
Since IEEE is a respectable source and the paper is a couple years old, it would surprise me that there is a typo. However, I do not understand how this formula can work. It does seem to me that the second inequation would always be wrong at least for some $i$ if the first one is true.
Am I misunderstanding how the filter works or is it a typo in the paper?