本文選題：實時視頻傳輸 + 碼率動態(tài)調整��； 參考：《重慶大學》2014年碩士論文

【摘要】：在3G網絡中傳輸實時視頻是一種典型的應用。相比于其他業(yè)務，視頻信息的數據量大，傳輸之前必須經過壓縮。目前最常用的壓縮標準為H.264，經過H.264壓縮后的視頻流可以在3G網絡信道上獲得較好的傳輸效果。但是由于3G網絡帶寬不穩(wěn)定，且抖動明顯，因此，如何根據3G網絡帶寬變化情況，動態(tài)調整H.264碼率控制策略，以取得更佳的視頻傳輸效果，獲得更好的用戶體驗，是移動網絡視頻傳輸技術中值得研究的一個問題。 論文工作圍繞實時視頻通信中發(fā)送端可能獲取的網絡狀態(tài)信息，從網絡帶寬預測的角度來動態(tài)調節(jié)視頻碼率，并根據幀的重要程度不同，實施有選擇的丟幀策略，以期取得更好的視頻傳輸體驗。論文主要開展了以下一些工作： ①分析了實時視頻通信中視頻發(fā)送端可能感知的網絡帶寬參數，建立一種視頻編碼碼率控制的模型。該模型根據發(fā)送端緩沖區(qū)比特流的大小，預期的網絡帶寬和變化趨勢，來調整和控制相應的H.264碼率控制指標。 ②在以上模型基礎上，提出了針對模型中不同處理階段的優(yōu)化策略。針對編碼碼率頻繁切換對移動終端帶來的處理開銷問題，實施碼率分等級變換方式；通過設定和監(jiān)測相關參數閾值，實施發(fā)送緩沖區(qū)管理策略；根據H.264編碼后的幀重要性不同，在3G網絡出現擁塞情況時，根據幀的重要性不同而采取優(yōu)先丟棄非關鍵幀的幀丟棄策略。 ③采用JM平臺和VCEG-N80離線環(huán)境，開展了仿真實驗，以檢驗所提出方法在網絡帶寬預測方面的有效性。通過測量丟包率計算PSNR值的實驗，，比較了傳統(tǒng)傳輸模式與論文改進模式下實時視頻傳輸效果的不同，驗證了論文所提出改進方法的有效性。
[Abstract]:It is a typical application to transmit real-time video in 3G network. Compared with other services, video information has a large amount of data and must be compressed before it is transmitted. The most commonly used compression standard is H.264. The video stream compressed by H.264 can achieve better transmission effect in 3G network channel. However, because the bandwidth of 3G network is unstable and jitter is obvious, how to dynamically adjust H.264 rate control strategy according to the change of 3G network bandwidth, in order to obtain better video transmission effect and better user experience, It is a problem worth studying in the video transmission technology of mobile network. This paper focuses on the network state information that may be acquired by the sender in real-time video communication, dynamically adjusts the video bit rate from the point of network bandwidth prediction, and implements a selective frame dropping strategy according to the importance of the frame. In order to achieve a better video transmission experience. The main work of this paper is as follows: 1 the network bandwidth parameters that the video sender may perceive in real-time video communication are analyzed and a video coding rate control model is established. The model adjusts and controls the corresponding H.264 rate control index according to the size of the buffer bit stream, the expected network bandwidth and the changing trend. An optimization strategy for different processing stages of the model is proposed. In order to solve the problem of processing overhead brought by frequent code rate switching to mobile terminal, the rate hierarchical transformation is implemented, and the transmission buffer management strategy is implemented by setting and monitoring the threshold of relevant parameters. According to the different importance of H. 264 encoded frame, When there is congestion in 3G network, according to the importance of frame, the strategy of dropping non-key frame first is adopted. 3 the simulation experiment is carried out using JM platform and VCEG-N80 off-line environment. The effectiveness of the proposed method in network bandwidth prediction is verified. Through the experiment of calculating PSNR value by measuring the packet loss rate, the differences between the traditional transmission mode and the improved mode of real-time video transmission are compared, and the effectiveness of the improved method proposed in this paper is verified.
【學位授予單位】：重慶大學
【學位級別】：碩士
【學位授予年份】：2014
【分類號】：TN919.8

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