研究同儕式視訊串流系統中之封包重要性與封包多樣性之取捨

Abstract

近幾年，同儕式多媒體視訊串流的成功已經有目共睹。儘管如此，如何在這樣的系統架構之下設計一個視覺滿意度導向之區塊排班演算法仍然尚未被解決。不像是傳統客戶與伺服器的架構，在同儕式架構下使用者必須互相交換彼次的視訊區塊以得到完整可撥放的視訊內容。倘若我們優先將系統的頻寬配置給重要的視訊區塊，那麼系統就很容易陷入所謂的內容瓶頸現象。此現象會隨著系統使用者的增加而變得更嚴重。此論文我們將確立這個問題並且了解其背後的原因。之後，我們將提出一個結合資料分散導向以及集中重要區塊導向之動態切換的區塊排班演算法。模擬結果顯示，相較於現存的排班演算法，我們所提出的方式不但可以改善視訊品質同時也可以撐得住大量的使用者。

During recent years, the success of live swarm-based P2P streaming system has been witnessed. Nevertheless, how to design an effective mechanism in mitigating video quality degradation in an error-prone overlay network is still not thoroughly resolved yet. Unlike conventional client-server paradigm, there is data availability problem in swarm-based P2P streaming system. If we directly conduct the importance-first scheduling strategy (i.e. let the chunks with most distortion-rate efficiency get scheduled first) in swarm-based P2P streaming system, the serious content bottleneck for low priority chunks occurs, particularly when the population size is large. In this paper, we first identify the unique problem and understand the rationale behind. After that, a dynamic strategy-switching approach that combines the advantages of random and importance-first scheduling strategy is proposed. Simulation results indicate that compared with existing approaches our approach not only provides better scheduling efficiency, but also is scalable even when population size is large.