使用視訊編碼技術提升雙模行動裝置視訊品質之研究

近年來，由於無線網路技術的蓬勃發展，新一代掌上型行動裝置均配有多模無線介面來使用各種網路應用，其中透過視訊串流來收看各種影音節目更是一重要的應用。針對傳統無線網路的缺失，已有許多研究提出以多個無線網路來提升網路效能，進而提升視訊畫質。然而目前這些多模網路的研究，大多著重於使用如封包排程等各層網路協定技術，以期達到提升視訊品質與傳統多模網路研究不同，本論文針對雙模 (WiFi及3G) 行動裝置，研究不同的視訊編碼技術，比較並討論其如何利用雙網以提升效能。本論文使用三種不同的視訊編碼標準技術包含有MPEG-4 Simple Profile，FGS及H.264並討論其技術之差異，了解各種編碼技術在WiFi網路所得的效能，接著在探討如何利用各種技術之特性使其能有效率的使用3G網路使得視訊品質在雙網中得以大幅提升。針對MPEG-4，由於I畫面較P畫面重要，便於3G及WiFi網路各傳送一份I畫面來提升對於I畫面的保護，由模擬結果顯示可提升10% I畫面的接收率及視訊品質1~2 dB。其次，FGS可依重要性將資料分成基礎層以及增強層，便可將較重要的基礎層傳送至QoS的網路。模擬顯示，畫面接收率可由12.8%降至5%，而視訊品質提升3至5 dB。最後H.264除了傳統壓縮方式之餘，亦使用了不同的錯誤防護工具來降低網路的不可靠因素對其產生的影響。其中FMO可將一個畫面分成幾個更小但相互獨立的片段，將經過FMO處理過的I畫面傳送到兩個網路上便可更加提升I畫面的接收成功率。由模擬結果可發現I畫面遺失率由15%降至7%而視訊品質提升3至4dB。由上述結果顯示，使用雙網可有效改善視訊品質。

關鍵字

雙網；視訊串流；視訊編碼

並列摘要

Multi-path video streaming is a solution for overcoming the limit of error-prone networks. Traditional multi-path researches focus on di®erent networking technologies such as packet scheduling. This thesis, however, compares different video coding standards such as MPEG-4 Simple Pro‾le, FGS, and H.264 with the goals of enhancing the video quality on dual mode mobile devices. We ‾rst evaluate the performance in the WiFi network. Then we discuss how to use the 3G bandwidth e±ciently to enhance the video quality on dual mode mobile devices. Because the I frame is more important than P frame in MPEG-4. The I frame is transmitted to WiFi and 3G to increase its protection. The reception of the I frame is increasing 10% and there is an enhancement of 1 ~ 2 dB. As for FGS, it can separate a frame into the base layer and the enhancement layer. Because the base layer is much important than the enhancement layer, the base layer is transmitted into WiFi and 3G to increase the reception of the I frame. The reception of the I frame has been enhanced from 12.8% to 5%. H.264 has several error resilience tools to utilize such as FMO and data partition. FMO is one of these tools and it can separate a frame into several smaller independent slices. The I frame that is enhanced robustness by FMO is transmitted to 3G and WiFi, so the I frame loss is decreased from 15% ~ 7%.

並列關鍵字

dual networks ； video streaming ； video coding

參考文獻

[22]

[3] Nlanr/dast : Iperf - the tcp/udp bandwidth measurement tool. Online available

meeting, January 2007.

diversity for multiple description video communication," IEEE Inter. Conf. on

[8] L. Cai, X. Liu, and W. Badawy, Hierarchical adaptive control scheme for video

國際替代計量

使用視訊編碼技術提升雙模行動裝置視訊品質之研究

全文下載

主題瀏覽