Method and apparatus for adaptive loop filter processing of reconstructed video

Methods and apparatus for geometric transformation by neighbouring difference reordering. According to one method, a current sample among the reconstructed pixels in the current block and a set of filter samples surrounding the current sample are determined. Difference measures are derived for at least a partial set of filter samples, where each of the difference measures is related to sample differences between a pair of respective filter samples and the current sample, and the pair of respective filter samples are located symmetrically with respect to the current sample. At least a partial set of ALF coefficients are assigned to at least the partial set of filter samples according to the difference measures. According to another method, a target geometric transformation is determined from a set of geometric transformations according to an index. A filtered block is then derived by applying the target geometric transformation to the current reconstructed pixels.