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研究生：	莊峻富 Zhuang, Jun-Fu
論文名稱：	一聯合式物件基礎MPEG-4位元率控制方法 A Joint Object-Based Rate Control Method in MPEG-4
指導教授：	陳進興 Chen, Chin-Hsing
學位類別：	碩士 Master
系所名稱：	電機資訊學院 - 電機工程學系 Department of Electrical Engineering
論文出版年：	2003
畢業學年度：	91
語文別：	英文
論文頁數：	78
中文關鍵詞：	位元率控制
外文關鍵詞：	Rate Control, Bit Allocation, MPEG-4
相關次數：	點閱：61 下載：2
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近年來，網路多媒體的位元率控制成了相當熱門的研究。一般來說，位元率控制包含了兩個部分，一個是位元的分配，另一是使用分配到的位元來求得一個適當的量化參數值，對整張圖像或單一個區塊進行編碼。MPEG編碼器裡的位元控制演算法是基於一二次位元-失真函數，在這個模型下，位元與失真為量化參數的函數，因而，它們的關係為非線性且計算複雜。

此篇論文，基於一線性位元失真模型提出一物件基礎位元率控制架構。我們將線性位元率模型應用於物件導向影像編碼上，並建構一新的α因子來分配適當的位元量給每個物件或圖像。我們提出的架構主要貢獻包括(1)調控量化參數值，(2)新的位元分配決策因子及(3)混合式的位元分配策略。

實驗結果顯示，我們的方法不僅比VM18需要較少的計算量，更能產生較平滑的編碼品質。在較低的位元率下，我們的方法不但能編出較多的圖像，且擁有較好的平均PSNR值。

Video coding rate control has been the interests of research in recent years. General speaking, rate control includes two parts, one is bit allocation and the other is to find an appropriate q value to encode a frame or macroblock using the allocated bits. The rate control algorithm of the MPEG encoder is based on a quadratic formulation of the rate-distortion function. In this model, bit rate and distortion are expressed in terms of the quantization parameter. However, their relation is non-linear and has great computation complexity.

In this thesis, we develop an object-based rate control framework based on the linear -domain R-D model. For coupling with the -domain linear rate model and making it applicable to MPEG-4 object-based video coding, we construct a novel α factor to allocate appropriate bits for each object or frame. The contributions of our proposed framework include (1) regulation of the q value (2) a new decision factor and (3) the hybrid bit allocation strategy.

Experiments show our method not only requires less computation but also generates smoother coding output when compared with the VM18. In lower bit rate, our method codes more frames than VM18, yet still produces much higher average PSNR in most cases.

Abstract……………………………………………………………I
Contents…………………………………………………………III
Figure Captions…………………………………………………VI
Table Captions…………………………………………………VII

Chapter 1 Introduction…………………………………………1
1 Motivation……………………………………………………1
2 Recent Works…………………………………………………2
3 Thesis Organization…………………………………………3

Chapter 2 Overview of the MPEG-4 System and Its Video 
          Encoder…………………………………………………4
1 MPEG-4 System…………………………………………………4
1.1 Compression Layer…………………………………………5
1.2 Synchronization Layer……………………………………7
1.3 Delivery Layer……………………………………………7
2 MPEG-4 Video Encoder………………………………………8
2.1 Intra Frame Coding Techniques…………………………10
2.2 Inter Frame Coding Techniques…………………………15
3 Summary…………………………………………………………18
Chapter 3 Rate Control Methods and Analysis………………20
1 Why Rate Control?……………………………………………20
2 Rate-Distortion Analysis…………………………………21
2.1 R-D Curve……………………………………………………22
2.2 R-q Curve and D-q Curve…………………………………24
3 Frame-Level Rate Control…………………………………25
3.1 Initialization……………………………………………27
3.2 Bit Allocation……………………………………………27
3.3 Determining Quantization Parameter…………………29
3.4 Updating……………………………………………………29
4 Multiple Video Object Rate Control……………………30
4.1 Initialization……………………………………………31
4.2 Bit Allocation……………………………………………32
4.3 Computing VOP-Level q Value……………………………33
5 MB-Level Rate Control………………………………………35
5.1 Distributing Bits for Each Macroblock………………36
5.2 Computing the MB-Level q Value………………………37
6 Summary…………………………………………………………38

Chapter 4 The Proposed Object-Based Rate Control 
          Framework………………………………………………39
1 Drawbacks of the q-Domain Model…………………………39
2 The  -Domain R-D Model……………………………………40
2.1 Linear  -Domain Rate Model……………………………42
3 The Proposed Object-Based Rate Control Framework
    Using the Linear  -Domain Model…………………………43
3.1 The Proposed Object-Based Rate Control……………44
3.2 Analysis of Model Parameters…………………………48
4 Overview of Bit Allocation………………………………51
4.1 Why Bit Allocation?………………………………………51
4.2 Bit Allocation in MPEG…………………………………51
5 The Proposed Hybrid Bit Allocation Method……………53
5.1 The α Factor………………………………………………53
5.2 Frame-Level Bit Allocation Model……………………54
5.3 VOP-Level Bit Allocation Model………………………55
5.4 Buffer Control……………………………………………57
5.5 The Proposed Hybrid Bit Allocation…………………59
6 Summary…………………………………………………………61

Chapter 5 Experiment Results and Conclusion………………63
1 Configuration Setting………………………………………63
2 Experiment Results…………………………………………63
3 Discussions……………………………………………………75
4 Conclusions……………………………………………………75

References…………………………………………………………76

                                    

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[2] ISO/IEC 14496-6, Coding of Audio-Visual Objects: Delivery Multimedia Integration Framework, Final Draft International Standard, ISO/IEC JTC1/SC29/WG11 N2506, October 1998.

[3] Video Group, “MPEG-4 Video Verification Model version 18.0,” ISO/IEC JTC 1/SC 29/WG 11, Coding of Moving Pictures and Associated Audio MPEG 2001/N3908, Pisa, Italy, January 2001.

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[8] Z. He, S. Mitra, “A Unified Rate-Distortion Analysis Framework for Transform Coding,“ IEEE Trans. Circuits Syst. Video Tech., pp. 1221-1236, Vol. 11, No. 12, Dec. 2001.

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[10] L. –J. Lin, A. Ortega, “Bit-Rate Control Using Piecewise Approximated Rate-Distortion Characteristics,” IEEE Trans. Circuits Syst. Video Tech., pp. 446-459, Vol. 8, No. 4, Aug. 1998.

[11] H. Lee, T. Chiang, Y. –Q. Zhang, “Scalable Rate Control for MPEG-4 Video,” IEEE Trans. Circuits Syst. Video Tech., pp. 878-894, Vol. 10, No. 6, Sep. 2000.

[12] Z. Lei, N. –D. Georganas, “Accurate Bit Allocation and Rate Control for DCT Domain Video Transcoding,” Proceedings of the 2002 IEEE Canadian Conference on Electrical & Computer Engineering, pp. 968-973.

[13] J. –R. Corbera, S. Lei, “Rate Control in DCT Video Coding for Low-Delay Communications,” IEEE Trans. Circuits Syst. Video Tech., pp. 172-185, Vol. 9, No. 1, Feb 1999.

[14] B. Tao, W. Dickinson, H. –A. Peterson, “Adaptive Model-Driven Bit Allocation for MPEG Video Coding,” IEEE Trans. Circuits Syst. Video Tech., pp. 147-157, Vol. 10, No.1, Feb. 2000.

[15] A. Vetro, H. Sun, Y. Wang, “MPEG-4 Rate Control for Multiple Video Objects,” IEEE Trans. Circuits Syst. Video Tech., pp. 1243-1258, Vol. 9, No. 8, Dec 1999.

[16] A. Vetro and H. Sun, “An overview of MPEG-4 object-based encoding algorithms,” Proceedings of Information Technology: Coding and Computing, pp. 366-369, 2001.

[17] A. Vetro, Y. Wang, H. Sun, “Rate-Distortion Modeling for Multiscale Binary Shape Coding Based on Markov Random Fields,” IEEE Trans. on Image Processing, Vol. XX, No. Y, Apr. 2001.

[18] J. Wiseman, “An Introduction to MPEG Video Compression,” http://members.aol.com/symbandgrl

[19] D. Wu, Y. –T. Hou, W. Zhu, H. –J. Lee, T. Chiang, Y. –Q. Zhang, H. –J. Chao, “On End-to-End Architecture for Transporting MPEG-4 Video Over the Internet,” IEEE Trans. Circuits Syst. Video Tech., pp. 923-941, Vol. 10, No. 6, Sep 2000.

[20] B. Xie, W. Zeng, “Sequence-Based Rate Control for Constant Quality Video,” IEEE ICIP 2002, pp. 77-80.

[21] 戴顯權, “資料壓縮,” 紳藍出版, 2001

校內：2004-07-31公開
校外：2004-07-31公開

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