臺灣博碩士論文加值系統

在一般的多點視訊會議中，參加人員為眾人焦點所在，而非背景。並且運動量大的參加者會受到較多的注意。因此，我們提出一種基於物件特性將被限制之位元率分配給各物件的方法。我們希望讓複雜度高、運動量大的物件分配到較大的位元率，使之擁有較高的畫質。反之，複雜度較低、運動量較小的物件分配到較少的位元率，使之畫質降低。由於複雜度高、運動量大的物件會受較高的注意力，而複雜度較低、運動量較小的物件受較小注意力，因此整個畫面的視覺效果便能提升。而此方法根據ITU-T TMN8的位元率與失真模型推導出位元率與失真的最佳化之物件位元率分配，其中考慮了物件複雜度。另外，我們引入了物件運動量及物件大小的因素推導出聯合的位元率分配方法。實驗的結果證明了使用此方法之後，較引人興趣之物件的畫質被提昇，同時較不引人興趣之物件的畫質被降低。
本論文中，我們提出兩種基於物件之多點虛擬視訊會議環境以提供更真實的會議，分別為二維虛擬場景會議與三維虛擬環境會議。在二維虛擬場景會議中，物件被改變大小，並放置在預先設計的二維虛擬場景。而在三維虛擬環境會議中，物件根據其相對位置被組合放置在三維虛擬環境。本論文中，我們並提出一物件分割的程序來將物件由視訊影像中分離出來。其中，我們使用背景相減、形態學運算子、行列掃描等方法。

In a general multipoint video conferencing, the participants focus on the other participants rather than the background, and they will pay more attention on the active conferees. Therefore, we propose a bit-allocation method which may distribute the constrained bit-rates to each object based on its characteristics. From the rate and distortion model proposed in ITU-T TMN8, we derive an object-based R-D optimized bit allocation equation, which only considers spatial activity. Then we introduce the factors of temporal activity and object size into the bit allocation equation to derive the joint bit-allocation method. Simulation results show that the image quality of interest is improved while the image quality of less interest is degraded. In this thesis, two multipoint virtual conferencing environments are proposed to provide a more realistic conference, the conferencing with two-dimensional virtual scene and the conferencing with three-dimensional virtual environment. In the conferencing with two-dimensional virtual scene, the objects are resized and composed onto a pre-designed virtual scene. In the conferencing with three-dimensional virtual environment, the objects are manipulated onto a three-dimensional environment based on their specific locations. An object-segmentation procedure is also proposed in this thesis to discriminate the objects from the video sequence based on the background subtraction, morphological operations, and row-column scan method.

Chapter 1 Introduction2
1.1 Multipoint Video Conference2
1.2 Motivation2
1.3 Thesis Organization2
Chapter 2 H.263 Based Video Transcoding for Multipoint Video Conference2
2.1 Overview of H.263 Video Coding Standard2
2.2 Video Transcoding Architectures2
2.3 TMN-8 Rate and Distortion Model2
2.3.1 . Rate Model2
2.3.2 . Distortion Model2
2.3.3 Optimized Quantization Parameter2
Chapter 3 Object-based Video Transcoding with Chroma-Keying2
3.1 Object-based Video Processing Using Chroma-Keying2
3.2 R-D Optimized Bit Allocation for Video Objects2
3.3 Simulation Results2
Chapter 4 Object-based Virtual Video Conferencing Environments2
4.1 Overview of Proposed Object-based Virtual Video Conferencing Environments2
4.1.1 . Virtual video conferencing with two-dimensional scene2
4.1.2 . Virtual video conferencing in three-dimensional environment2
4.2 Object Segmentation Based on Background Subtraction Method2
4.3 Construction of three-dimensional Environment Using Open GL2
Chapter 5 Conclusions2
Bibliography2

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