臺灣博碩士論文加值系統

在最近幾年，由於網際網路與行動裝置的快速發展與普及，對於實時影音串流(real time video streaming)的需求日漸增多，例如現場直播、線上會議、遠距教學等，為了確保視訊在傳輸過程中的穩定性與順暢度，必須不斷發展與制定新的視訊串流協議來保證傳輸品質的維持。
在眾多的協議中，本論文選擇分析WebRTC的視訊傳輸效能，因為WebRTC的普及度甚高，在傳輸延遲部分也是到目前為止仍可被接受的協議之ㄧ。影響WebRTC傳輸效能的因素很多，本論文利用自行架設的WebRTC即時通訊系統，並繪製出WebRTC的函式呼叫圖，再藉由此函式呼叫圖進一步分析出WebRTC四個主要模組，分別為SDP、DTLS、ICE、及SRTP的可能效能瓶頸(Possible Performance Bottlenecks)。最後實驗結果顯示SDP的可能效能瓶頸在函式PushdownMediaDescription。DTLS與SRTP兩者可能效能瓶頸在函式OnReadPacket及OnSentPacket。最後ICE的可能效能瓶頸為函式HandleInComing及OnReadPacket。

In recent years, the rapid development and widespread use of the Internet and mobile devices have led to a growing demand for real-time video streaming, for applications such as live broadcasts, online meetings, and distance learning. To ensure stability and fluidity in video transmission, it is necessary to continuously develop and formulate new video streaming protocols to ensure the maintenance of transmission quality.
Among various protocols, thesis chose to analyze the video transmission performance of WebRTC. WebRTC is highly popular, and its transmission latency remains acceptable to date. Several factors influence the performance of WebRTC. In this study, we established a WebRTC real-time communication system and drew a function call graph of WebRTC. Through this graph, we further analyzed the possible performance bottlenecks of the four major modules of WebRTC, namely, SDP, DTLS, ICE, and SRTP. The final results suggest that the potential performance bottleneck in SDP is in the PushdownMediaDescription function. Both DTLS and SRTP appear to have potential performance bottlenecks in the OnReadPacket and OnSentPacket functions. Finally, for ICE, potential performance bottlenecks are seen in the HandleInComing and OnReadPacket functions.

摘要 iii
致謝 vi
目錄 vii
表目錄 ix
圖目錄 x
第一章、 緒論 1
1.1 研究背景與動機 1
1.2 相關研究 2
1.3 方法概述 4
1.4 論文架構 5
第二章、 相關技術介紹 6
2.1 FFmpeg 6
2.2 防火牆簡介(Firewall) 7
2.3 函式呼叫圖(Call Graph) 10
2.4 WebRTC 12
第三章、 研究方法 18
3.1 研究架構及流程圖 18
3.2 WebRTC的建置架設 19
3.3 函式呼叫圖及函式執行時的時間計算 24
3.4 WebRTC溝通模組的架構圖 31
第四章、 實驗結果與討論 37
4.1 實驗環境 37
4.2 測試結果與分析 38
第五章、 結論與未來工作 50
5.1 結論 50
5.2 未來工作 50
參考文獻 51

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