利用編碼區塊樣式於H.264可變區塊大小之快速模式決策

Using Coded Block Patterns for Fast Variable Block-Size Mode Selection in H.264

陳柏源(Bo-Yuan Chen)

指導教授 ： 楊士萱

國立臺北科技大學/電資學院/資訊工程系研究所/碩士(2007年)

https://doi.org/10.6841/NTUT.2007.00299

摘要

H.264視訊編碼標準在做動作估計時，將畫面間的模式選擇(inter-mode selection)放寬至16x16~4x4等7種分割模式。此分割模式的放寬，雖然改善了壓縮效能，卻也提高了編碼端運算的複雜度，對於即時視訊的應用無疑是一大挑戰。因此，本論文引入了空間域的編碼區塊樣式(coded block pattern)和時間域的預測動作向量 (predicted motion vectors)等觀念，提供了一個快速的畫面間模式選擇演算法。編碼區塊樣式用來描述編碼區塊與最佳參考區塊之間的殘差(residual)影像是否需要編碼，透過編碼區塊樣式的資訊，我們可以提前了解此區塊的平滑程度；而比較預測動作向量和實際編碼產生動作向量的關聯性，可以判別此編碼區塊移動的一致性。平滑和移動一致的區塊可以用大的區塊類型描述之，而不需要徹底搜尋(exhaustive search)。本論文提出的演算法不需要額外的計算，且可與現有的各式快速動作估計演算法結合。實驗結果顯示，我們所提出的演算法可以在不大影響影像品質的前提下，加快了編碼速度約60%。

關鍵字

H.264 ； 畫面間的模式選擇 ； 編碼區塊樣式 ； 快速動作估計

並列摘要

The H.264 video coding standard supports the inter-mode selection, i.e., blocks of different sizes ranging from 16´16 to 4´4 can be used in motion estimation. Although the inter-mode flexibility significantly improves the compression performance, the search of the best mode is computation demanding and imposes a big challenge on real-time conversational video services. To resolve the performance-complexity dilemma, a priori knowledge of the coding blocks such as their spatial or temporal homogeneity, may be intelligently employed. In this thesis, we present a fast inter-mode decision algorithm based on the coded block patterns (CBPs) and the predicted motion vectors (PMV). We determine the spatial homogeneity of a block from its CBPs, which is a complexity indicator of the residual image block. We then compare the PMV with the true motion vector to identify temporally stationary regions. A spatially homogeneous or temporally stationary region will choose a larger block size without exhaustive search. The proposed method can be seamlessly integrated with the H.264 JM reference software without additional computational load. Experimental results show that the proposed method achieves more than 60% reduction in computation time relative to the exhaustive search, respectively. Furthermore, the incurred degradation in visual quality is almost.

並列關鍵字

H.264 ； inter-mode selection ； coded block pattern ； fast motion estimation

參考文獻

[1] ITU-T Recommendation H.261, Video Codec for Audiovisual Services at p x 64 kbit/s, March 1993.

[3] ISO/IEC International Standard 13818-2, Generic coding of moving pictures and associated audio – Part 2: Video, 1995.

[4] ITU-T Recommendation H.263, Video Coding for Low Bit Rate Communication, version 1, Nov. 1995; version2, Jan. 1998; version 3, Nov. 2000.

[7] G. J. Sullivan and T. Wiegand, “Video compression-from concepts to the H.264/AVC standard,” Proceedings of the IEEE, vol. 93, no. 1, pp. 18-31, Jan. 2005.

[8] D. Marpe, T. Wiegard, and G. J. Sullivan, “The H.264/MPEG4 advanced video coding standard and its applications,” IEEE Communications Magazine, vol. 44, no.8, pp. 134-143, Aug. 2006.