臺灣博碩士論文加值系統

相較於H.264/AVC，最新的高效率視訊編碼 (HEVC) 提供了更高的視訊壓縮性能，能夠維持幾乎相同的重建視訊品質，減少了50% 的資料位元率。但是，這也導致了HEVC的複雜性大大增加，與H.264 / AVC的9種畫面內預測模式比較，HEVC增加為35種畫面內預測模式來提高畫面內編碼性能，進而導致高計算複雜度。
本論文提出一種基於方向性的編碼單元 (CU) 分割提早終止，以及畫面內預測模式的快速決策方法。判斷編碼單元中像素點與其相鄰四個方位鄰居像素間亮度差值的絕對值之累加，再與門檻值進行比較，來提早終止編碼單元的分割，以及改善快速模式決策法以減少在編碼過程之粗略模式決策步驟中的畫面內預測之候選模式數量，來達成畫面內預測編碼時間節省之目的。
實驗結果顯示出我們提出的方法與 HEVC 參考軟體 HM16.20 的方法比較，平均能減少 47.63% 的編碼時間，並且僅有平均 2.75% 的編碼位元率增加，以及平均 0.15dB 的重建視訊畫面品質損失。

Compared with H.264/AVC, the latest High Efficiency Video Coding (HEVC) improves the compression performance by 50% data-rate reduction on average and maintains the similar quality of reconstructed video. HEVC uses a quad-tree based structure to represent the video frame partitioned into variable-sized coding units (CUs). Discovering the optimal coding unit partition in terms of the rate-distortion cost function is one of the most computationally challenging parts of the HEVC encoder. Compared with 9 intra-frame prediction modes in H.264/AVC, HEVC has increased to 35 intra-frame prediction modes to improve intra-frame coding performance, while increasing the coding complexity greatly.
This paper proposes an early termination of coding unit partition and an algorithm of improving intra-frame prediction mode decision. The scheme of accumulation of the absolute difference between the pixels in the coding unit and its neighboring pixels of four adjacent orientations compared to a threshold value is utilized to determine whether the partition of the coding unit is terminated early. And, a fast mode decision algorithm is improved to reduce the number of candidate modes in the rough mode decision (RMD) process for HEVC intra-frame prediction to achieve the encoding time saved more.
The experimental results show that compared with the algorithm of the HEVC reference software HM16.20, the proposed method can save the encoding time on average by 47.63% with only the average Bjontegaard delta bit-rate (BD-BR) of 2.75% increasing and the average Bjontegaard delta peak-signal-to-noise ratio (BD-PSNR) of 0.15dB quality loss for the reconstructed video.

摘要..........................................i
ABSTRACT..........................................ii
誌謝..........................................iv
目錄..........................................v
英文簡寫說明..........................................vi
中英文對照表..........................................ix
圖目錄..........................................xiii
表目錄..........................................xv
第一章 緒論..........................................1
1.1 研究背景..........................................1
1.2 研究動機與目的..........................................2
1.3 論文架構..........................................3
第二章 HEVC視訊編碼標準介紹..........................................4
2.1 HEVC視訊編碼概述..........................................4
2.2 HEVC視訊編碼架構..........................................8
2.3四元樹分割法 (Quad-tree Structure)..........................................12
2.3.1編碼單元 (Coding Unit, CU)..........................................13
2.3.2預測單元 (Prediction Unit, PU)..........................................15
2.3.3轉換單元 (Transform Unit, TU)..........................................17
2.4階層編碼結構..........................................18
第三章 我們提出的方法..........................................21
3.1編碼單元分割提早終止的相關研究..........................................21
3.2畫面內預測之快速模式決策的相關研究..........................................24
3.3我們所提出的方法..........................................27
第四章 實驗模擬與效能比較..........................................31
4.1緒論..........................................31
4.2實驗環境..........................................31
4.3測試視訊序列..........................................31
4.4實驗結果..........................................42
4.5效能比較..........................................55
第五章 結論..........................................62
參考文獻..........................................63

[1]G. J. Sullivan, J.-R. Ohm, W.-J. Han, and T. Wiegand, "Overview of the high efficiency video coding (HEVC) standard," IEEE Transactions on circuits and systems for video technology, vol. 22, no. 12, pp. 1649-1668, 2012.
[2]T. Wiegand, G. J. Sullivan, G. Bjontegaard, and A. Luthra, "Overview of the H. 264/AVC video coding standard," IEEE Transactions on circuits and systems for video technology, vol. 13, no. 7, pp. 560-576, 2003.
[3]Y. Xu and X. Huang, "Hardware-oriented fast CU size and prediction mode decision algorithm for HEVC intra prediction," in 2019 IEEE 5th International Conference for Convergence in Technology (I2CT), 2019, pp. 1-5.
[4]X. Zhou, G. Shi, and W. Zhou, "Perceptual CU size decision and fast prediction mode decision algorithm for HEVC intra coding," in 2016 IEEE International Symposium on Multimedia (ISM), 2016, pp. 375-378.
[5]H. Zhang and Z. Ma, "Fast intra mode decision for high efficiency video coding (HEVC)," IEEE Transactions on circuits and systems for video technology, vol. 24, no. 4, pp. 660-668, 2013.
[6]L. Zhao, L. Zhang, S. Ma, and D. Zhao, "Fast mode decision algorithm for intra prediction in HEVC," in 2011 Visual Communications and Image Processing (VCIP), 2011, pp. 1-4.
[7] HM, HEVC Test Model, Available: https://hevc.hhi.fraunhofer.de/svn/svn_HEVCSoftware/tags/