高效率視訊編碼(High Efficient Video Coding, HEVC)技術的進步，雖可提高視訊的壓縮比，但卻增加編碼的複雜度。為因應不同網路頻寬的用戶，HEVC也制定延伸應用至可適性高效編碼(Scalable HEVC, SHVC)架構來提供不同頻寬的相應品質碼流，例如空間域可調(resolution scalable, RS)、品質域可調(quality scalable, QS)、以及時間域可調(temporal scalable, TS)的碼流。SHVC是編碼原始視訊產生一個基本層(Base Layer, BL)和一或數個增強層（Enhancement Layer, EL），因為在BL和EL中都必需決定CU、PU和TU的最佳編碼組合，因此SHVC所需運算複雜度又比HEVC更高。但在SHVC中預測當前區塊的編碼模式可利用層間(Inter-Layer, IL)編碼模式之關連性。本論文從訓練影片之SHVC碼流中擷取區塊編碼資訊，以統計性方法分析區塊編碼之IL關連性並提出了兩種快速編碼EL的策略：(1)快速深度決策:我們利用基礎層同位置CU的深度來決定增強層當前CU深度的測試範圍，進而提出兩種不同的深度測試範圍。並依照不同的編碼時間分為高加速模式與低加速模式; (2)快速預測模式決策:我們參考基礎層同位置CU的預測模式，依照基礎層與增強層間的關聯性將參考的預測模式分類，進而決定需要測試的預測模式。並提前判斷當前CU是否為SKIP模式，若為SKIP模式則跳過剩餘的模式與深度。實驗結果顯示將兩種方法結合在一起，高加速模式與低加速模式平均分別能減少76.71%和62.7%的增強層編碼時間。

The advancement of High Efficient Video Coding (HEVC) technology can improve video compression ratio, but increase coding complexity. To cope with users of different network bandwidths, HEVC also developed a Scalable HEVC (SHVC) architecture to provide corresponding quality streams of different bandwidths, such as resolution scalable (RS), quality scalable (QS), and temporal scalable (TS) streams. SHVC encodes the original video to produce a base layer(BL) and one or more enhancement layers(EL). SHVC requires more computational complexity than HEVC because the best coding combination of CU, PU, and TU must be decided in both BL and EL. However, prediction of the coding mode of the current block in SHVC may utilize the inter-layer (IL) coding mode. In this paper, the block coding information is extracted from the SHVC stream of the training video, the IL correlation of the block coding is analyzed statistically and two fast coding EL strategies are proposed: (1) We use the depth of base layer co-located CU to determine the depth testing range of enhancement layer current CU, and further propose two different depth testing range. And according to the different encoding time is divided into high acceleration mode and low acceleration mode. (2) Fast prediction mode decision: With reference to the prediction mode of the base layer co-located CU, we classify the reference prediction modes according to the correlation between the base layer and the enhancement layer to decide which prediction mode needs to be tested. And judge in advance if the current CU is SKIP mode, if the SKIP mode, skip over the remaining modes and depths in advance. The experimental results show that combining the two methods, the enhancement layer encoding time in high acceleration mode and low acceleration mode can be reduced by 76.71% and 62.7% on average, respectively.

[1] T. Wiegand et al, “Overview of the H.264/AVC video coding standard,” IEEE Trans. Circuits and Systems for Video Technology, vol. 13, no. 7, pp. 560-576, July 2003.
[2] H. Schwarz et al, “Overview of the scalable video coding extension of the H. 264/AVC standard,” IEEE Trans. circuits and systems for video technology, vol. 17, no. 9, pp. 1103-1120, Sep. 2007.
[3] G. J. Sullivan et al, “Overview of the high efficiency video coding (HEVC) standard,” IEEE Trans. Circuits and Systems for Video Technology, vol. 22, no. 12, pp. 1649-1668, Sep. 2012.
[4] J. M. Boyce et al, “Overview of SHVC: scalable extensions of the high efficiency video coding standard,” IEEE Trans. Circuits and Systems for Video Technology, vol. 26, no. 1, pp. 20-34, Jan. 2016.
[5] https://hevc.hhi.fraunhofer.de/shvc, [Jan. 18, 2018]
[6] J. Choi et al, “Fast coding unit decision method based on coding tree pruning for high efficiency video coding,” SPIE Optical Engineering, vol. 51, Issue 3, 2012.
[7] J. Lainema et al, “Intra coding of the HEVC Standard,” IEEE Trans. Circuits and Systems for Video Technology, vol. 22, no. 12, pp. 1792-1801, Dec 2012.
[8] http://www.hindawi.com/journals/ijrc/2012/473725/fig1/, [Jan. 18, 2018]
[9] X.-L. Tang et al, “An analysis of TZ search algorithm in JMVC,” IEEE Conf. Green Circuits and Systems (ICGCS), Shanghai, pp. 516-520, 2010.
[10] J.-F. Hu et al, “Speeding up the decisions of quad-tree structures and coding modes for HEVC coding units,” Institute of Computer and Communication Engineering Department of Electrical Engineering NCKU, June 2012.
[11] CABAC architecture. http://blog.sina.com.cn/s/blog_520811730101m9y2.html
[Jan. 18, 2018]
[12] J. Chen et al, “Scalable HEVC (SHVC) Test Model 7 (SHM 7),” document JCTVC-R1007. Sapporo, 2014.
[13] G. J. Sullivan et al, “Standardized extensions of high efficiency video coding (HEVC),” IEEE Journal of selected topics in Signal Processing vol. 7, no. 6, pp 1001-1016, 2013.
[14] H. Kibeya et al, “A fast coding algorithm based on fast mode decision for HEVC standard,” IEEE Conf. Sciences and Techniques of Automatic Control and Computer Engineering (STA), Dec 2013.
[15] Z. Yongfei et al, “Fast coding unit depth decision algorithm for interframe coding in HEVC,” IEEE Data Compression Conference, March 2013.
[16] J. H. Lee et al, “Fast encoding algorithm for high efficiency video coding (HEVC) system based on spatio-temporal correlation,” Journal of Real-Time Image Processing, pp 1-12, 2015.
[17] D. Wang et al, “Fast mode and depth decision algorithm for intra prediction of quality SHVC,” International Conference on Intelligent Computing. Springer International Publishing, 2014.
[18] X. Zuo et al, “Fast mode decision method for all intra spatial scalability in SHVC,” IEEE Visual Communications and Image Processing Conference, 2014.
[19] N. Shi et al, “Efficient mode decision algorithm for scalable high efficiency video coding,” SPIE/COS Photonics Asia. International Society for Optics and Photonics, 2014.
[20] R. Bailleul et al, “Fast mode decision for SNR scalability in SHVC digest of technical papers,” IEEE Conf. on Consumer Electronics, 2014.
[21] Q. Ge et al, “Fast encoding method using CU depth for quality scalable HEVC,” IEEE W. Advanced Research and Technology in Industry Applications, 2014.
[22] K. Kim et al, “Fast enhancement layer encoding method using cu depth correlation between adjacent layers for SHVC,” Journal of the Institute of Electronics and Information Engineers vol. 50, no. 6, pp. 260-264, 2013.
[23] X. Li et al, “An effective CU size decision method for quality scalability in SHVC,” Multimedia Tools and Applications, pp. 1-20, March 2016.
[24] H. Z. Tohidypour et al, “Fast mode assignment for quality scalable extension of the high efficiency video coding (HEVC) standard: a Bayesian approach,” Proc. Balkan Conference in Informatics. ACM, pp. 6165, Sep. 2013.
[25] H. R. Tohidypour et al, “Adaptive search range method for spatial scalable HEVC,” IEEE Conf. on Consumer Electronics, pp. 191–192, January 2014.
[26] W.-Ju Chiang, Jiann-Jone Chen, and Yao-Hong Tsai, “A fast SHVC coding scheme based on base layer co-located CU and cross-layer PU mode information,” IEEE International Conference Multimedia & Expo, 2017.
[27] G. Bjontegaard, “Calculation of Average PSNR Differences Between RD Curves,” ITU-T SG16/Q6 Document, VCEG-M33, Austin, April 2001.
[28] G. Bjontegaard, “Improvements of the BD-PSNR Model,” ITU-T SG16/Q6, Document, VCEG-AI11, Berlin, July 2008.
[29] H.-Yu Jiang, “Fast Intra Coding Unit Partition Decision in H. 266/FVC Based on Spatial Features,” PhD Thesis, National Central University, 2017.