1. A method for deblocking filtering a reconstructed picture in a video encoder or a video decoder, the method comprising: computing a first measure of deviation at a first four sample boundary segment covered by a first filtering sub-block of an 8×8 filtering block, wherein the first measure of deviation is computed using only samples of the reconstructed picture in the first filtering sub-block; using the first measure of deviation in deblocking filter decisions for the first four sample boundary segment; computing a second measure of deviation at a second four sample boundary segment covered by a second filtering sub-block of the 8×8 filtering block, wherein the second measure of deviation is computed using only samples of the reconstructed picture in the second filtering sub-block; and using the second measure of deviation in deblocking filter decisions for the second four sample boundary segment, wherein the first filtering sub-block is a top 8×4 filtering sub-block, the second filtering sub-block is a bottom 8×4 filtering sub-block, and the first and second four sample boundary segments are vertical boundary segments, or the first filtering sub-block is a left 4×8 filtering sub-block, the second filtering sub-block is a right 4×8 filtering sub-block, and the first and second four sample boundary segments are horizontal boundary segments.