P2P-based Delivery Method for Multi-Object Video and Its Evaluation

最近，互联网上的P2P视频传输变得越来越流行，因为Joost和Zatoo等服务已经启动。P2P视频传输的优势在于它可以减少服务器和网络负载，同时为用户提供出色的服务质量。这些已经开始的服务仅提供一种固定质量的视频的传送，但是存在许多类型的计算终端。因此，我们需要有效的视频传输方法，许多终端具有不同的计算能力，显示尺寸和带宽。已经有几项研究工作同时向具有不同质量要求的多个用户提供视频。在我们的研究项目中，我们提出了一种名为MTcast的视频传输方法，它通过依赖于用户对等点来转码和转发视频，从而实现对多个异构用户的高效视频广播。MTcast有几个优点。(i)它可以向每个用户提供其质量非常接近每个用户的请求的视频;（i i）它可以承受节点故障和突然离开;（iii）传送延迟与节点数目的对数成比例;以及（iv）新加入的节点不需要等待很长时间直到它第一次接收视频流。MTcast构造一棵树，其根是原始视频内容的发送者，作为完美n叉树的变体，其中具有更高质量要求的对等点位于树的根附近。根据物理路径的带宽和拓扑结构来确定节点之间的父子关系，并利用Java语言构建了一个MTcast系统的原型系统，在PlanetLab上运行，验证了MTcast在真实的Internet环境中的实用性和有效性。通过原型系统，我们证实了MTcast实现了短的启动延迟、短的信道切换时间和短的对等点离开/故障恢复时间

Recently, P2P video delivery on the Internet is becoming popular as several services like Joost and Zatoo has been started. The advantage of P2P video delivery is that it can reduce server and network loads while providing excellent service quality to the users. These already started services only provide delivery of one fixed quality of video, but there are many types of computing terminals. Thus, we need efficient video delivery methods for many terminals with different computation powers, display sizes and bandwidths. There are already several research efforts on simultaneously delivering videos to multiple users with different quality requirements. In our research project, we have proposed a video delivery method named MTcast which achieves efficient video broadcast to multiple heterogeneous users by relying on user peers to transcode and forward video. There are several advantages of MTcast. (i) it can provide a video whose quality is very close to the request of each user to each user ; (ii) it can withstand with node failure and abrupt departure ; (iii) the delivery delay is proportional to the logarithm of the number of nodes ; and (iv) newly joined nodes need not to wait long until it first receives the video stream. MTcast constructs a tree whose root is the sender of the original video content as a variation of a perfect n-ary tree, where peers with higher quality requirements are located near the root of the tree. The parent-child relationship between peers is decided according to bandwidth and topology of physical path. We also constructed a prototype system of MTcast system using Java language, which can be used on PlanetLab, and validated practicability and effectiveness of MTcast in the real Internet environment. With the prototype system, we confirmed that MTcast achieves short start-up latency, small channel switching time, and small recovery time from peer leaving/failure