臺灣博碩士論文加值系統

在目前的網際網路發展中，泛用多媒體存取服務是相當重要的一個應用，然而，為了有效的在網路上傳送多媒體內容，我們必須考慮到兩種因素，那就是網路的異質性 (例如：有線及無線網路、電話網路、及行動通訊網路等) 跟不同的使用者裝置 (例如：個人電腦、行動電話、手持式裝置等)，這兩種因素會影響客戶所需的視訊串流的位元率，後來可調式視訊編碼被提出來有效的應付這兩種因素，因此可調式視訊編碼對於泛用多媒體存而言是相當的重要。目前JVT團隊正在制訂H.264可調式編碼的標準，在H.264可調式編碼中，adaptive GOP structure (AGS)的技術被提出來用來改善編碼效率，其主要針對的視訊內容是有較大且較複雜的物體運動向量，但是這個方法的缺點是會大量的增加編碼的運算複雜度。
在這篇論文中，我們提出一個能夠有效的降低AGS的運算複雜度的演算法，原來AGS的方法必須考慮到所有可能的GOP尺寸，因此必須執行更多的運動補償時間軸濾波技術(motion-compensated temporal filtering, MCTF)，這是增加運算複雜度的主要原因。在我們提出的演算法中，做完最大GOP尺寸的MCTF之後，我們會利用兩個特徵來決定是否要繼續執行後續所有的其他小GOP尺寸的MCTF，因此我們提出的方法可以避免執行不必要的MCTF和最後選擇GOP mode的程序，實驗證實這樣的方法可以有效的減少AGS的運算複雜度，並且維持一定的視訊品質。

The universal multimedia access service (UMA) is an important application of internet. However, to effectively transmit video contents through networks, we must consider two issues: heterogeneous networks and various access devices. These two issues could affect the bit-rate of transmitted video streams and so the scalable video coding (SVC) is proposed for handling these two issues. Currently, for scalable video coding, H.264 scalable extension is standardized by the Joint Video Team (JVT), which is formed with ISO/IEC MPEG and ITU-T VCEG. In H.264 scalable extension, adaptive GOP structure (AGS) is used to improve coding efficiency for the video content with larger temporal variations. However, the enormous coding complexity is a major drawback of AGS.
In this thesis, we propose a fast GOP mode selection algorithm to effectively reduce the coding complexity of AGS in H.264 scalable extension. AGS needs to consider motion-compensated temporal filtering (MCTF) procedures of all possible GOP sizes. Therefore, the computational complexity will enormously increase with the more of MCTF procedures. In our proposed algorithm for AGS, after executing the first MCTF procedure with a full-sized GOP (a GOP which has the maximum GOP size), we utilize two features to decrease unnecessary MCTF procedures of sub-GOPs (GOPs which have smaller GOP sizes) for reducing the coding complexity. Experimental results show that our proposed algorithm can effectively reduce the coding complexity of AGS, but with slight decrease in PSNR.

Table of Contents
Chapter 1 Introduction………………………………………………………………...1
1.1 Scalable Video Coding.....................................................................................1
1.2 MPEG-21 SVC................................................................................................3
1.3 Organization of this thesis................................................................................4
Chapter 2 Overview on the Related Topics…………………………………………....5
2.1 The Scalable Extension of H.264/AVC............................................................5
2.1.1 Encoder Structure of Scalable Video Coding Standard.........................5
2.1.2 Motion-Compensated Temporal Filtering (MCTF)…………………...6
2.1.3 Temporal Scalability of MCTF............................................................10
2.1.4 Hierarchical B Pictures........................................................................12
2.2 Adaptive GOP Structure for H.264 Scalable Extension.................................13
2.2.1 Motivation...........................................................................................13
2.2.2 Adaptive GOP Structure......................................................................17
2.2.3 Mode Selection Algorithm..................................................................18
Chapter 3 The Proposed Fast Mode Selection Algorithm for AGS in H.264 Scalable Extension......................................................................................................................22
3.1 Feature Selection for Fast Mode Selection of AGS.......................................22
3.2 Proposed Fast Mode Selection Algorithm for AGS.......................................30
Chapter 4 Experimental Results...................................................................................33
Chapter 5 Conclusion...................................................................................................39
Reference.....................................................................................................................40

Reference

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[16]G.H. Park, M.W. Park, S Jeong, K. Kim, and J. Hong, “Improve SVC Coding Efficiency by Adaptive GOP Structure (SVC CE2),” ISO/IEC JTC1/SC29/WG11 and ITU-T SG16 Q.6, JVT-O018, 2005.

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