A method and a circuit for adaptive loop filtering in a video coding system are described. The method can include receiving a block of samples generated from a previous-stage filter circuit in a filter pipeline, the block of samples being one of multiple blocks included in a current picture, performing, in parallel, adaptive loop filter (ALF) processing for multiple target samples in the block of samples, while the previous-stage filter circuit is simultaneously processing another block in the current picture, storing, in a buffer, first samples each having a filter input area defined by a filter shape that includes at least one sample which has not been received, and storing, in the buffer, second samples included in the filter input areas of the first samples.