In one embodiment, the method includes obtaining a block type of the second block and the third block. The second block is adjacent to the first block horizontally, and the third block is adjacent to the first block vertically. The method further includes determining whether the second and third blocks have non-zero transform coefficient information if the block type of the second and third blocks, respectively, are not an intra-coded block. A horizontal filter strength value and vertical filter strength values are determined based on the above steps. The blocking phenomenon in the first block is removed according to the horizontal filter strength value firstly, then vertical filter strength value secondly.