同儕式網路電視中改善轉台效能及播放品質之研究

Abstract

網路電視在最近幾年已經成為一種很普遍的網際網路多媒體應用，隨著網路速度的提升，傳送的影音畫質也持續的改善。在傳統的用戶伺服器架構下，會因為用戶數的增加而需要更高的硬體成本來提供服務。因此許多網路電視便應用同儕式網路(Peer-to-Peer)的架構來實現服務，藉由每個使用者分享自己的資源以及頻寬，來達到節省成本及容易分享的目的。然而因為每個使用者可以輕易的加入及退出同儕式網路，常常會造成網路電視的品質不穩定，也因為在轉台時，需要重新搜尋其它的影音來源，造成轉台的時間過長，因此降低了一般使用者觀看的意願。在轉台的時候，如何能夠在最短的時間之內找到適合的提供服務的來源，將能夠縮短資料下載的時間，整體的效能及穩定度也能夠明顯的提升。 在本篇論文中，我們針對影音來源的選擇以及每個使用者的資源如何分享給其它使用者，提出了一套改善的機制，以IP位址比對及封包測試的方式來篩選出較佳的資源提供者，並且改用主動推送影音資料的方式，來改善轉台過程中的延遲，並且利用不用的資料緩衝區來提升播放的穩定度。我們利用OMNET++來建構並模擬我們所提出的機制，數據結果顯示我們所提出的方法可以有效的降低轉台延遲及改善影音播放品質。

In recent years, IPTV has become a popular Internet multimedia application. As network bandwidth increases quickly, the media playback quality is also improved continuously. In the traditional client-server structure, the service cost may become too high if the number of clients goes large. Therefore, many IPTV services are deployed based on the P2P structure. The service provider can save a lot of cost on both the server equipment and bandwidth requirement by using each peer's resource and bandwidth. Since the peer may join and leave the P2P system arbitrarily, it may cause the quality of P2P IPTV unstable. The long channel switching delay also reduces the user's willingness of watching. To find the best qualified resource provider will reduce the download time and improve the playback quality and efficiency. In this thesis, we propose approaches to select the partner peers which have the larger available bandwidth by comparing the IP address and using probing packets, and reduce the switching delay by pushing the video chunk. We also use two buffers that store the different channel data to improve the stability of the video playback. We use the OMNET++ simulator to evaluate our proposed P2P system, and the numerical results show that our proposed schemes can significantly reduce the channel switching delay and perform video playback smoothly.