High Efficiency Video Coding (HEVC)是一種新一代的視訊壓縮技術，近年來由JCT-VC (ISO/IEC MPEG和 ITU-TVCEG)所開發與制定，其編碼效率相較於過去的視訊壓縮標準H.264/AVC有大幅的提升，僅需約H.264/AVC之50%的位元率，即能達到與之相同的影像品質。
HEVC中可變式的轉換單位(Transform unit, TU)，其預設大小從4x4到32x32，並採用四分樹狀編碼結構(Residual Quad-tree)提供更多編碼區塊大小以適應畫面特性，雖然提供更好的編碼效能，但因其複雜的編碼架構，相對地大幅增加運算複雜度。然而視訊編碼複雜度隨著解析度的增加不斷提升，因此發展TU模式之快速決策演算法是非常重要的議題之一。
本論文提供一個轉換單位模式之快速決策演算法，其演算法利用轉換前的殘餘值資訊提前做決策，總共分為兩部分探討：首先第一部份利用相同區塊之不同預測模式下的殘餘值去判斷是否提前終止該預測模式下之TU流程；第二部分為利用殘餘值差異之特性來判斷子區塊之差異性，提前跳過或是提前終止該轉換單位之編碼；最後搭配參考[3]所提出之零區塊偵測法來提前中止轉換單位之編碼。整合起來後即可達到省下不必要的TU模式來降低編碼端的運算時間。本論文所提出之方法在Low Delay P的配置下總時間平均節省約18.82%，而BD-BR僅提升0.469%，並且在轉換單位上平均節省的時間約64.07%，最高的視訊影像則省了75.64%的轉換單位時間。

High Efficiency Video Coding (HEVC) is the latest standard of video compression. The residual quadtree (RQT) coding structure, which provides many kinds of transform size for various characteristics of video, is adopted in HEVC to achieve high coding efficiency. However, compared with previous standards, HEVC increase encoding complexity significantly due to the advanced encoding structure. Thus, to develop a method that can efficiently reduce TU encoding time is necessary.
A Fast TU Mode Decision Algorithm Based on Residual Difference is proposed in this thesis to reduce the computational complexity. The proposed algorithm utilized the residual difference to develop the criterion of early TU skip and termination. The threshold was trained by the first few samples of sequence, which will be affected by sequence characteristic and QPs. Experimental results showed that the proposed algorithm saves at most 75.64% TU encoding time and on average 64.07% TU encoding time compared with HM 15.0 in low delay P main and the loss of average BD-BR is no more than 0.5%.

目錄
摘要 I
ABSTRACT II
誌謝 III
目錄 V
附圖索引 VIII
附表索引 X
第一章 緒論 1
1.1 研究背景 1
1.2 研究動機與目的 1
1.3 論文架構 2
第二章 HEVC 視訊編碼標準介紹 3
2.1 HEVC 視訊編碼介紹 3
2.1.1 HEVC與H.264/AVC差異 3
2.1.2 編碼流程介紹 4
2.2 HEVC視訊編碼架構介紹 5
2.2.1 編碼單位 (Coding Unit, CU) 5
2.2.2 預測單位 (Prediction Unit, PU) 7
2.2.2.1 畫面內預測 (Intra prediction) 8
2.2.2.2 畫面間預測 (Inter prediction) 10
2.2.3 轉換單位 (Transform Unit, TU) 11
2.2.3.1 轉換 (Transform) 12
2.2.3.2 量化 (Quantization) 13
2.2.4 殘餘四分樹 (Residual Quad-tree) 14
2.3 HEVC 環境設定及視訊樣本介紹 15
2.3.1 環境設定 15
2.3.2 視訊樣本介紹 17
第三章 HEVC轉換單位之快速演算法相關研究介紹 22
3.1 HEVC複雜度分析 22
3.2 HEVC之TU快速演算法相關文獻 23
3.2.1 基於轉換量化係數之相關文獻 24
3.2.2 基於其他資訊之相關文獻 27
第四章 基於殘餘值差異之轉換單位快速決策演算法 30
4.1 殘餘值差異 (RESIDUAL DIFFERENCE) 30
4.1.1 殘餘值差異分析 30
4.1.1.1 QP對殘餘值差異之影響 32
4.1.1.2 切割與不切割數量比例對殘餘值差異之影響 34
4.1.2 殘餘值差異之快速決策 35
4.1.3 臨界值選取 36
4.2 移除冗餘搜索 (REDUNDANT SEARCH REMOVING) 40
4.3 零區塊偵測 (ZERO BLOCK DETECTION) 42
4.3.1 零區塊統計及分析 42
4.3.2零區塊偵測法 44
4.4 所提之快速決策流程 46
第五章 實驗結果與分析討論 49
5.1 實驗環境設置 49
5.2 實驗結果 50
第六章 結論與未來展望 54
參考文獻 55

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