架構於H.264之可適應性去方塊效應濾波器演算法

由於現今多媒體的普及，造就了視訊壓縮的技術在日常生活中不可或缺的地位，其中方塊壓縮搭配動態補償以去除空間域上的重複資訊，被廣泛的應用在各種不同的壓縮標準，如JPEG、MPEG-1/2/4、H.264/AVC。方塊壓縮不只可以使能量更緊密的結合在一起與去相關性外，更可以降低多餘的編碼冗餘。雖然方塊壓縮可以達到不錯的壓縮率，但是在低位元率或高度量化的離散餘弦係數狀況下，容易在方塊邊界處發生方塊與方塊之間的不連續現象，也就是所謂的方塊效應。為了降低此效應對視訊影像的影響，H.264/AVC視訊壓縮標準，把去方塊效應濾波器置入於編解碼的壓縮標準當中，也就是提供了內迴圈（loop filter）濾波器來解決方塊效應。在本篇論文中，我們提出一個架構於H.264/AVC視訊壓縮標準的可適應性去方塊效應演算法，如果所需去方塊效應演算法之參數與臨界值不適合，方塊效應問題將不能有效的被解決，經由壓縮後之視訊品質也不能被接受。我們提出之去方塊效應演算法不僅可以降低方塊效應，也可以因為使用了有效的搜尋補償參數演算法降低了編碼所需的時間。我們的演算法擁有了較低的計算複雜度與正確的補償參數。經由實驗的結果顯示，我們所提出的演算法可以提升重建的視訊品質與降低方塊效應，在處理動態成分較多的影像時，比H.264/AVC JM10.2 所提供的去方塊效應演算法減少約10%的編碼時間。

關鍵字

方塊效應；低通濾波器； H.264/AVC ；動態補償

並列摘要

The video compression technology is more important, because the digital multimedia is widely used in our life. Block-based video coding cooperating with block transform and block motion compensation is the most widely adopted way to reduce the data redundancy in various video coding standards such as JPEG, MPEG-1/2/4, and H.264/AVC. Not only energy is compacted and de-corrected but also redundancy information is reduced. Although block structure gains data compression, it results in blocking effect which impacts the quality of compressed video. In general, block compressed technology can usually obtain acceptable quality of video but suffer from annoying blocking artifacts when it becomes worse especially in the low bit rate or high quantization parameter video environment. H.264/AVC standards include the deblocking filters inside its coding loop, in order to reduce the block effect for the visual quality of images or videos. In this work, we propose an adaptive deblocking filter algorithm to reduce blocking effect for H.264 video coding system. If block effect can not be solved, the quality of compressed video must be bad even it sets parameters and thresholds appropriately. We not only propose a deblocking filter algorithm for reducing block effect but also present an effective search algorithm to reduce coding time. The advantages of our proposed algorithm are the lower complexity of computation and better offsetA and offsetB of possession in slice level. Experiment results show that our proposed method can improve visual quality of reconstructed video. We present an adaptive deblocking filter algorithm to reduce blocking effect and reduce coding times than the JM10.2 by about 10%.

並列關鍵字

Blocking Effect ； Low Pass Filter ； H.264/AVC ； Motion Compensation

參考文獻

[1] ITU-T Recommendation H.261, “Video codec for audiovisual Services at p X 64 kbit/s,” March 1993.

[4] ITU-T Recommendation H.263, “Video coding for low bit rate communication,” version 1, Nov. 1995; version 2, Jan. 1998; version 3, Nov. 2000.

[7] W. F. Cheung and Y. H. Chan, “Improving MPEG-4 coding performance by jointly optimizing compression and blocking effect elimination,” IEE Proceedings-Vision, Image and Signal Processing, vol. 148, pp.194-201, June 2001.

[8] T. Jarske, P. Haacisto and I. Defee, “Post-filtering method for reducing blocking effects from coded images,” IEEE Transactions on Consumer Electronics, vol. 40, no. 8 pp. 521-526, August 1994.

[11] S. A. Karunasekera and N. G. Kingsbury, “A Distortion measure for blocking artifacts in images based on human visual sensitivity,” IEEE Trans on Image Processing,pp. 713-724, June 1995.

國際替代計量

架構於H.264之可適應性去方塊效應濾波器演算法

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