臺灣博碩士論文加值系統

現有的視訊壓縮標準通常使用以區塊離散餘弦轉換（ＤＣＴ）及動態補償預測（ＭＣＰ）以去除空間及時序上的重複資訊。在低位元率下，高度量化的ＤＣＴ係數在轉回空間域後容易在區塊邊界處發生不連續現象（區塊效應），而動態補償預測則可能將此不連續現象擴散到區塊內部，而使偵測變得困難。
因動態補償預測引起的區塊效應可使用迴路濾波器解決，它是一種整合於編解碼器內部的濾波器，濾波後的影像會被用於預測。惟迴路濾波器較不具彈性，使用者無法自由決定是否開啟之，而受限於所接收到的檔案。在本研究中，我們提出了新的後處理濾波器來解決此問題。
為了估測區塊內部的不連續現象，我們使用了動態補償的方式，所有檢測出的區塊現象位置都會被暫存。結合移動向量和先前視訊影像中檢測出的區塊現象位置，將可以正確估測出區塊內部不連續現象可能的發生位置，配合具方向性的區塊效應偵測及濾波，可以後處理濾波器實現迴路濾波器的效能。所提的方法可以使用於Ｈ．２６４及其他以ＤＣＴ及ＭＣＰ為編碼基礎的各種視訊。

Most video coding standards use block-based discrete cosine transform (DCT)and motion-compensated prediction (MCP) to reduce both spatial redundancy andtemporal. For very low bit rate coding, coarse-quantized DCT coefficients suffer discontinuities at block boundaries, namely blocking artifact, after reverse transform. Furthermore, motion-compensated prediction propagates blocking artifacts to inner-block regions, which makes artifact detection difficult.
Blocking artifacts caused by motion-compensated prediction can be solved by a loop-filter, which is integrated to the codec and filtered frames are used as reference frames. The main drawback of loop-filter is its in-flexibility, i.e., users cannot enable/disable filtering freely but restricted by the received bitstream. In this study, a hybrid deblocking filter for H.264 video is proposed.
To estimate inner-block discontinuities, a motion-compensated based approach is proposed. A map of detected blocking artifacts within each video frame is stored. Combining motion vectors and blocking artifact maps of previous frames, possible locations where blocking artifacts may occur can be estimated. Cooperating with oriented blocking artifact detecting and filtering, we successfully realize loop-filter performance with a post-filter. The proposed approach can also used in other DCT/MCP based codecs.

摘 要.............................................................................................................................i
ABSTRACT .................................................................................................................ii
ACKNOWLEDGMENTS..........................................................................................iv
TABLE OF CONTENTS............................................................................................v
LIST OF FIGURES...................................................................................................vii
LIST OF TABLES.....................................................................................................xii
CHAPTER 1 INTRODUCTION.............................................................................1
1.1 Motivation...................................................................................................1
1.2 Survey of Related Researches.....................................................................3
1.3 Overview of Proposed Approach................................................................9
1.4 Thesis Organization ..................................................................................10
CHAPTER 2 H.264 VIDEO COMPRESSION STANDARD AND ITS
DEBLOCKING FILTER TECHNIQUES ...................................11
2.1 H.264 Video Compression Standard ........................................................11
2.1.1 Overview of H.264 video..................................................................11
2.1.2 H.264 video compression techniques ...............................................11
2.1.3 Syntax and data organization of H.264 video...................................17
2.2 Deblocking Filter Process .........................................................................25
CHAPTER 3 PROPOSED HYBRID DEBLOCKING FILTER FOR H.264
VIDEO .............................................................................................29
3.1 Architecture...............................................................................................29
3.2 Orientation ................................................................................................30
3.3 Blocking Detection ...................................................................................33
3.4 Motion Compensation...............................................................................37
- vi-
3.5 Filtring.......................................................................................................39
3.5.1 Filtering for Bs=0..............................................................................40
3.5.2 Filtering for Bs=1..............................................................................41
CHAPTER 4 SIMULATION RESULTS.............................................................44
4.1 Blocking Detection Precision....................................................................45
4.2 Subjective Quality .....................................................................................48
4.2.1 Intra-coded frame deblocking performance comparison..................48
4.2.2 Inter-coded frame deblocking performance comparison..................54
4.2.3 Detailed View ...................................................................................60
4.2.4 Compared to H.264 Loop Filter........................................................60
4.3 Objective Quality ......................................................................................61
4.4 Processing Time ........................................................................................64
CHAPTER 5 DISCUSSIONS AND CONCLUSIONS........................................65
5.1 Discussions................................................................................................65
5.2 Conclusions...............................................................................................66
REFERENCES..........................................................................................................67

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