Method and apparatus for Adaptive Loop Filter with alternative luma classifier for video coding

Methods and apparatus for video coding using ALF (Adaptive Loop Filter) with alternative band classifier or a new classifier derived from two or more classifiers. According to one method, a block value is determined for an ALF classification block of the current block. The block value is mapped to a target block classification class using a lookup table. A filtered output is derived by applying a target filter to a current reconstructed pixel in the ALF classification block, where the target filter is selected from a set of ALFs according to the target block classification class. Filtered-reconstructed pixels are provided, where the filtered-reconstructed pixels comprise the filtered output. According to another method, a new classifier is generated from two or more different classifiers. A target filter is determined from a set of ALFs for an ALF classification block using the new classifier.