Research On The Theory And Algorithm Of Deblocking Filter In Video Coding

Block-based hybrid coding is the main structure of video coding now and in the near further. Because it compresses the blocks relatively separated, there is a big disadvatange of this structure, that is obvious blocking artifacts will appear when the compression ratio is high. Deblocking filter can reduce blocking artifacts efficiently, thus improve the subject quality significiantly. Deblocking filter is a useful and improtiant technique is video coding.In this paper, we firstly introduce the Human Visual System (HVS), and some of its characteristics which is related to video compression. Then we introduce the main subject distortions, which are blocking artifacts, ringing artifacts and basis pattern breakthrough. These are basises of designing a deblocking filter.Next chapter, we analyze the reasons why blocking artifact is induced. We find that there are two main reasons:1. Transform coding of the intra/inter preidiction coefficient.2. Discontinued motion compensation.In this chapter, we also calculate the distribution of the distortion, and its relationship with other coding parameters.There are mainly two types of deblocking filter: post deblocking filter and in-loop deblocking filter. Chapter 4 and 5 intruduce and analyze the state-of-art technique of these two type deblocking filter. In chapter 4, an advanced post deblocking filter - the deblocking filter in MPEG4 appendex F is introduced and analyzed. In chapter 5, the newest in-loop deblocking filter - the deblocking filter in H.264 is shown and analyzed.In chapter 6, based on the analyse in chapter 4 and 5 combined with the result in chapter 3, we proposed a simple but efficient in-loop deblocking filter for AVS part 7. Even though the proposed deblocking filter's complexity is lower than that of H.264's deblocking filter, it can provide high subject quality, and only a little PSNR lose is observed. This technique is adopted by AVS standard part 7.In the last chapter, the possible further research direction of deblocking filter is also pointed out in this chapter.