陳少傑臺灣大學：電機工程學研究所彭冠舉Peng, Guan-JuGuan-JuPeng2007-11-262018-07-062007-11-262018-07-062006http://ntur.lib.ntu.edu.tw//handle/246246/53354中文摘要 隨著無線網路的普及，透過無線網路的視訊傳輸變成非常重要的課題。相較於有線網路，無線網路的資料傳輸較不穩定，頻寬較小且更容易隨著使用者所處的環境而變化。所以無線網路對於影像傳輸而言，無疑地是更為嚴苛的傳輸環境。因此，對於期望維持品質的視訊傳輸而言，必須要提供能夠隨著頻寬的波動而改變影像壓縮碼率的方法，以期能夠有效利用頻寬，而達到影像品質最佳化、減少延遲以及增強畫面平滑性的效果。 在本論文中，我們結合了排隊理論、H.264/AVC以及相對應的碼率控制機制，提出無線視訊碼率控制之排隊模型。目的在於針對不同的頻寬，能夠估計出在該頻寬下最適合之碼率。排隊理論用以描述視訊資料在編碼端暫存記憶體中的處裡情形，並據此結合目前頻寬估計出最適碼率。H.264/AVC在編碼效能上相較於之前的視訊壓縮標準有著顯著的進步，而在許多的即時視訊應用中，往往必須在極短的時間內處理龐大的資料。因此，如H.264/AVC一般，高效率的視訊壓縮技術是必須的。除此之外，針對H.264/AVC設計的碼率控制機制，讓實際碼率能夠確實的逼近由排隊理論估計出的最適視訊碼率。藉由這樣的設計，我們讓視訊品質、延遲以及視訊畫面平滑性同時獲得合理的控制，並且能夠符合即時視訊傳輸的標準。ABSTRACT With the prevailing of wireless communication, transmission of video applications through wireless network becomes an important issue. Comparing to wired network, the data transmission is more unstable and the bandwidth is less in wireless network. Thus, video transmission over wireless network becomes more challenging. Since available bandwidth during transmission varies frequently, in order to maintain the video quality and utilize the available bandwidth, a method which modifies video bitrate with varying bandwidth is required. In this Thesis, we combine queuing theory, H.264/AVC standard and corresponding rate control scheme to achieve this purpose. We build a video bit rate control queuing model to describe the buffer behavior of the encoder. Then deduce the appropriate video bitrate form this model. The experimental results show that this method not only reaches the balance between acceptable latency and the video quality, but also utilizes the memory of handheld device.TABLE OF CONTENTS ABSTRACT i LIST OF FIGURES v LIST OF TABLES vii 1. INTRODUCTION 1 1.1 Applications of Video Transmission in Wireless Environment 1 1.2 Proposed System Architecture For Wireless Conversation Services 3 1.3 Thesis Organization 4 2. OVERVIEW OF H.264/AVC IN WIRELESS ENVIRONMENR 6 2.1 H.264/AVC 6 2.1.1 Profiles and Level of H.264/AVC 7 2.1.2 Video Structure in H.264 9 2.1.3 Basic Coding Structure of H.264/AVC 10 2.1.4 Network Abstraction Layer 12 2.2 Transportation of H.264 Video in Wireless Environment 13 2.3 Rate Control 16 2.3.1 Basic Concepts of Rate Control 16 2.3.2 Rate Control of H.264/AVC 17 2.3.2.1 Rate-Quantization Model 17 2.3.2.2 Complexity Estimation 18 2.3.2.3 Bit Allocation 19 2.3.2.4 ΔQP Limiter 19 2.4 Previous Channel Joint Rate Control Algorithm 19 3. WIRELESS VIDEO BITRATE CONTROL QUEUING MODEL 21 3.1 Characteristics of Queuing Processes 21 3.2 Notation of Queuing Systems ……… 24 3.3 Encoder System Queuing Model 26 3.4 M/M/1/K Queuing Model 27 3.5 G/M/1 Queuing Model 31 3.5.1 Analysis of G/M/1 Queuing Model 31 3.5.2 M/M/1 Queuing Model 34 3.5.3 D/M/1 Queuing Model 35 3.6 Analysis of Encoder Queuing System with Computer Simulation 35 4. SIMULATION OF REAL TIME WIRELESS VIDEO APPLICATIONS 39 4.1 Queue Based Video Rate Control 39 4.2 Performance Evaluation of the M/M/1K Model 41 4.3 Performance Evaluation of the D/M/1 Model 46 4.4 Summarization 50 5. CONCLUSION 53 REFERENCE 551115753 bytesapplication/pdfen-US影像壓縮碼率控制video codingrate controlthesishttp://ntur.lib.ntu.edu.tw/bitstream/246246/53354/1/ntu-95-R93921042-1.pdf