Efficient quadtree based block-shift filtering for deblocking and deringing

The existing implementations of block shift based filtering algorithms for deblocking are hard to achieve good smoothing performance and low computation complexity simultaneously due to their fixed block size and small shifting range. In this paper, we propose to integrate quadtree (QT) decomposition with the block-shift filtering for deblocking. By incorporating the QT decomposition, we can easily find the locations of uniform regions and determine the corresponding suitable block sizes. The variable block sizes generated by the QT decomposition facilitate the later block-shift filtering with low computational cost. In addition, large block based shift filtering can provide better deblocking results because the smoothing range of large blocks spans over the conventional 8× 8 block size. Furthermore, we extend the proposed QT based block-shifting algorithm for deringing JPEG2000 coded images. Experimental results show the superior performance of our proposed algorithms.