【摘要】：當今社會人們對視頻傳輸?shù)囊笤絹碓礁?隨著技術的發(fā)展,基于HTTP(Hypertext Transfer Protocol)的動態(tài)自適應流媒體技術越來越受到人們的關注。基于HTTP的動態(tài)自適應視頻流傳輸(DASH:Dynamic Adaptive Streaming based on HTTP)的技術原理是把相同的視頻編碼為多份不同質量的視頻文件,然后把這些文件分為很多的視頻分段存儲在服務器端,在流媒體傳輸過程中,客戶端可以根據(jù)當前帶寬變化來選擇適應此網(wǎng)絡帶寬的質量分段進行傳輸。但是,DASH標準并沒有規(guī)定客戶端選擇視頻文件分段時所應采取的策略,這使得客戶端可以決定采取什么策略來進行高效的傳輸,特別是針對時變性很強的無線信道而言�？蛻舳巳绾胃鶕�(jù)時變的無線網(wǎng)絡帶寬選擇合適的視頻質量分段成為了當今流媒體傳輸技術的一個研究熱點。本文在前人工作的基礎上,進一步研究了基于馬爾科夫決策過程理論的流媒體傳輸系統(tǒng)模型,基于模型求解得到最優(yōu)傳輸策略。重點討論和分析了在自適應傳輸過程中,分段質量和播放時限是如何影響最佳策略的,并分析了在馬爾科夫決策過程理論模型中,下載時間離散化對系統(tǒng)模型準確度的影響。本文研究的主要內(nèi)容為:1.參考國內(nèi)外已有研究工作,對馬爾科夫決策過程理論(MDP)進行學習與總結,進一步研究了流媒體傳輸中的馬爾科夫決策過程系統(tǒng)建模。2.基于該模型,求解得到無線網(wǎng)絡流媒體傳輸過程中的最優(yōu)傳輸策略,即根據(jù)當前系統(tǒng)狀態(tài)選擇最優(yōu)的視頻分段質量,以期達到最好的用戶觀看體驗。3.基于最優(yōu)策略,設計仿真程序進行仿真,驗證了最優(yōu)策略的有效性,并通過仿真分析了系統(tǒng)模型在計算中存在的誤差因素,即系統(tǒng)狀態(tài)離散化帶來的誤差。
[Abstract]:With the development of technology, the dynamic adaptive streaming media technology based on HTTP (Hypertext Transfer Protocol) has attracted more and more attention. Dynamic Adaptive Video Stream Transmission based on HTTP (the principle of DASH:Dynamic Adaptive Streaming based on HTTP) is to encode the same video into multiple video files of different quality, and then divide these files into many video segments and store them on the server side. In the process of streaming media transmission, the client can select the quality segment which adapts to the network bandwidth according to the current bandwidth change. However, the DASH standard does not specify the strategy to be adopted when the client selects video file segmentation, which enables the client to decide what strategy to adopt for efficient transmission, especially for the time-varying wireless channel. How to select the appropriate video quality segment according to the time-varying wireless network bandwidth has become a hot topic in streaming media transmission technology. In this paper, based on the previous work, the model of streaming media transmission system based on Markov decision process theory is further studied, and the optimal transmission strategy is obtained based on the solution of the model. This paper mainly discusses and analyzes how segment quality and playback time affect the optimal strategy in adaptive transmission, and analyzes the influence of download time discretization on the accuracy of system model in Markov decision process theory model. The main contents of this paper are: 1: 1. Referring to the existing research work at home and abroad, the Markov decision process theory (MDP) is studied and summarized, and the Markov decision process modeling in streaming media transmission is further studied. Based on this model, the optimal transmission strategy in the process of streaming media transmission in wireless network is solved, that is, the optimal video segment quality is selected according to the current system state, in order to achieve the best user viewing experience. 3. Based on the optimal strategy, a simulation program is designed to verify the effectiveness of the optimal strategy, and the error factors in the calculation of the system model are analyzed by simulation, that is, the error caused by the discretization of the system state.
【學位授予單位】：西華師范大學
【學位級別】：碩士
【學位授予年份】：2017
【分類號】：TN919.8

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