一种基于节点可选度的P2P点播流媒体数据调度算法

当前的P2P(Peer-to-Peer)点播流媒体系统中数据调度算法未能充分利用每个用户节点自身的特性.在分析典型数据调度算法基础上提出一种基于节点可选度的数据调度算法(SSP算法).该算法一方面在调度下载数据块时综合考虑了邻居节点带宽能力及其所拥有的数据信息.另一方面对服务节点的请求处理过程进行了优化.SSP算法有利于提高用户节点播放视频的连续性,降低流媒体服务器的负载压力,从而改善P2P点播流媒体系统的整体服务质量.仿真结果和实际应用表明算法性能良好,适用于用户节点能力差异较大的P2P点播流媒体环境.     

基于流媒体服务的视频监控系统设计

本文提出一种基于流媒体服务的视频监控系统方案。采用流媒体服务机制，在现有C／S模式的视频监控系统基础上，通过部署流媒体服务器．在多个用户并发访问同一路视频信号时，始终保证在流媒体和前端编码器链路上，只有一份数据拷贝在网络中传输，最大限度减小冗余数据包．提高数据传输效率．避免大容量的视频数据传输引起的网络拥塞。     

基于嵌入式Linux终端的在线流媒体服务系统

针对现有嵌入式Linux终端设备流媒体服务C/S模式的不足,实现了嵌入式Linux终端流媒体服务由C/S模式到B/S模式的改进。解决方法如下:影片参数添加到表单提交参数中,并通过表单提交进行节目点播;嵌入式Linux终端通过监听浏览器行为,截取用户请求信息,判断符合特定表单形式的request行为,并使用本地代码来完成mplayer播放器启动;mplayer接收影片参数,连接流媒体服务器并播放视频。解决了C/S模式下占用资源多、升级维护复杂及用户操作不方便的问题,实现了基于WEB形式的在线流媒体观看。     

一种高效点播流媒体服务器的设计与实现

流媒体网络传输的数据量大,并且用户访问流媒体服务器具有随机性和不确定性,因此流媒体服务器系统结构的设计必须合理,CPU、内存、I/O总线等各种资源的分配要合理,以便高效地为客户服务。本文通过缓冲区、线程池等技术对这几个方面加以分析、改进,并通过仿真实验Web证明了这些改进完全适合构建一个中等规模的点播流媒体服务器。     

Linux下WMV高性能IPTV流媒体服务器的设计与开发

流媒体点播技术定位于提供实时的文件点播服务,而WMV则是一种IPTV常用的文件格式。为了解决Linux或类Unix环境下对WMV文件格式的支持,设计了一个具有完全自主知识产权的支持WMV格式的Linux环境下的流媒体点播系统。该流媒体服务器采用创新的主从式架构设计,并设计了RTSP连接队列调度等算法,用来完善服务器的功能和提高服务器的性能。     

CDN在IPTV系统中的应用

如何提高用户对流媒体服务器的访问速度，缩短用户点播时延，流媒体服务器及其缓存服务器的部署已成为IPTV系统中的关键性问题。在本文中对IPTV系统和CDN相关技术的结构作简要介绍．并且介绍和分析如何把CDN相关技术应用到IPTV系统中去。     

视频点播服务器中服务策略的研究*

研讨了同时为多个点播用户服务的轮转服务策略和比例服务策略,并提出了VOD(video-on-demand)服务器在不破坏各路点播流实时播放率的前提下,应用这些服务策略的方法.     

基于UPnP技术设计的多媒体云服务最佳播放设备智能选取系统

当前,许多媒体服务供应商利用云技术向使用者提供流媒体云服务。云服务虽然提升了流媒体业务按需访问的便捷性,但用户在使用流媒体云服务的同时操作的智能化程度较低。用户在流媒体文件选择、媒体设备选择及服务器连接方面缺乏智能手段。此外,系统不具有媒体流播放的断点支持功能。本文利用即插即用网络通信协议UPnP,设计了一套最佳播放设备的智能选取模型。本模型通过分析比较媒体文件元数据与播放设备元数据,自动选取最佳的播放设备。同时,本模型通过断点信息的保存来实现媒体文件二次播放的连续性。本模型为流媒体云服务的断点播放和播放设备智能优化选取,提供了一种有效的技术模型。     

基于MMS的流媒体服务器系统性能的研究

随着计算机技术的发展,流媒体越来越广泛地应用于视频点播(VOD)系统中.介绍了基于MMS的流媒体服务器结构,对流媒体服务器点播、广播方式的性能进行了研究,重点研究了连接建立时间、节目响应时间与用户数量的关系,同时还研究了流媒体服务器物理内存容量对服务性能的影响,获得了定量的性能参数.     

一种可扩展的集群流媒体服务器

提出了一种可扩展的适合集群系统的流媒体服务器架构。在这个架构中,整个后台单机服务器是基于Apple公司的DarwinStreamingServer,而在前端开发了一个门户结点和多个中继结点,使整个后台服务器群基本能保持负载平衡、提供给用户高性能的流媒体服务。在外面用户看来整个系统就是一个高性能流媒体服务器。     

P2P流媒体技术飞速发展

P2P流媒体技术,也称为对等网络(peer-to-peer)技术,简单地说,就是一种用户不经过中继设备直接交换数据或服务的技术。它将目前互联网的"内容位于中心"模式改变为"内容位于边缘"模式,将权利交还给用户。在这种架构中,每个节点的地位都相同,具备客户端和服务器的双重特性,可以同时作为服务使用者和服务提供者。该文将为读者讲述在P2P流媒体技术的原理以及应用,希望能使大家对这种现阶段应用广泛,发展迅速的流媒体技术有一定的了解。     

XML语言在流媒体业务中的应用

宽带网络中最重要的增值业务是流媒体业务，传统的HTML浏览器已不适用于浏览流媒体信息。本文介绍了一种基于XML的流媒体信息描述和组织方案，基于该方案的客户端浏览器可以综合多种流式或非流式媒体信息，使用户能够非常便利的欣赏到交互流媒体服务。     

利用网格技术实现流媒体服务迁移

流媒体服务正在成为当今网络服务的代表性应用。为了提高流媒体服务的可用性,保证服务质量,快速高效的流迁移是研究中的重点和难点。本文探讨了流媒体服务迁移面临的关键问题,利用网格技术在实现流媒体服务迁移方面的优势。结合RTSP会话和流媒体传输监控技术,丈中在自发研制的流媒体服务网格NDSSG中实现了一个流媒体服务迁移系统,解决了因服务器故障造成的服务不可用问题以及可能的负载不平衡问题。在NDSSG中的实践证明：利用先进的网格技术可以实现高性能的流媒体服务迁移,可以有效提高流媒体服务的性能和质量。     

Quality-of-service oriented web service composition algorithm and planning architecture

In the next few decades, it is expected that web services will proliferate, many web services will offer the same services, and the clients will demand more value added and informative services rather than those offered by single, isolated web services. As the result, the problem of synthesizing web services of high quality will be raised as a prominent issue. The clients will face the trouble of choosing or creating composition plans, among numerous possible plans, that satisfy their quality-of-service (QoS) requirements. Typical QoS properties associated with a web service are the execution cost and time, availability, successful execution rate, reputation, and usage frequency. In engineering perspective, generating the composition plan that fulfills a client’s QoS requirement is a time-consuming optimization problem. To resolve the problem in a timely manner, we propose a constraint satisfaction based web service composition algorithm that combines tabu search and simulated annealing meta-heuristics. As an implementation framework of the algorithm, we suggest a QoS-oriented web service composition planning architecture. The architecture maintains expert made composition schemas in a service category and assists the client as pure user to choose the one he/she wants to use. The main modules of the architecture are composition broker and execution plan optimizer. With the aid of the UDDI server, the composition broker discovers candidate outsourced web services for each atomic process of the selected schema and gathers QoS information on the web services. After that, the execution plan optimizer runs the web service composition algorithm in order to generate a QoS-oriented composition plan. The performance of the algorithm was tested in a simulated environment.     

一个基于服务层叠网的分层服务组合框架

随着Internet上Web服务数量的不断增长,这些服务能够互联形成一个应用层的逻辑网络--服务层叠网(service overlay network,简称SON).基于SON,通过服务的组合提供增值服务,是满足用户动态、多变的功能及非功能需求的一种有效的方法.但是,已有基于SON的QoS感知的服务组合研究主要是面向服务间具有简单交互行为的应用领域,难以支持电子商务等具有复杂业务协作特征的应用场景.为此,通过使用业务协议刻画服务间的组合关系,从而构建更具普适性的SON;建立主动服务层叠网(active service overlay network,简称ASON)以实现可编程的服务层叠网,支持按需的服务组合;提出了一个基于主动服务层叠网的分层服务组合框架(hierachical service composition framework based on service overlay networks,简称HOSS),通过将业务协议(而不是消息)作为需求描述的基本单元,提升软件开发效率,并将服务组合需求映射为SON的动态用户视图以实现按需的组合.     

浅谈LoadRunner在网络流媒体中的应用

随着互联网的迅猛发展和普及为网络流媒体业务发展提供了强大市场动力,网络流媒体技术也得到了广泛的应用,用户对流媒体业务的质量需求也日益高涨。本文首先简单介绍什么是LoadRunner和它的工作原理以及什么是网络流媒体和网络流媒体的工作原理,然后介绍如何运用LoadRunner对网络流媒体的播放操作进行压力测试,研究分析测试结果,提出相应的解决方案。     

A unified benchmarking and model-based framework for building QoS-aware streaming media services

A number of technology and workload trends motivate us to consider the appropriate resource allocation mechanisms and policies for streaming media services in shared cluster environments. We present MediaGuard – a model-based infrastructure for building streaming media services – that can efficiently determine the fraction of server resources required to support a particular client request over its expected lifetime. The proposed solution is based on a unified cost function that uses a single value to reflect overall resource requirements such as the CPU, disk, memory, and bandwidth necessary to support a particular media stream based on its bit rate and whether it is likely to be served from memory or disk. We design a novel, time-segment-based memory model of a media server to efficiently determine in linear time whether a request will incur memory or disk access when given the history of previous accesses and the behavior of the server's main memory file buffer cache. Using the MediaGuard framework, we design two media services: (1) an efficient and accurate admission control service for streaming media servers that accounts for the impact of the server's main memory file buffer cache, and (2) a shared streaming media hosting service that can efficiently allocate the predefined shares of server resources to the hosted media services, while providing performance isolation and QoS guarantees among the hosted services. Our evaluation shows that, relative to a pessimistic admission control policy that assumes that all content must be served from disk, MediaGuard (as well as services that are built using it) deliver a factor of two improvement in server throughput.     

IMS 重叠网络多路径传输内容分发机制

基于IMS的流媒体业务通常以集中方式为终端客户提供直播、点播等内容服务.然而集中式的服务模式并不能充分利用资源,还会因为流量过于集中而拒绝为更多终端提供服务,甚至会因为媒体服务器的失效而影响业务.提出了一种基于IMS重叠网络支持多路径传输的内容分发机制,在传统IMS网络中通过引入重叠网络实现资源的共享与分发,提高了网络资源利用率、降低了中心媒体服务器负载.实验表明与传统媒体服务器为中心的内容分发机制相比基于IMS重叠网络的内容分发机制具有显著优势.     

A target advertisement system based on TV viewer’s profile reasoning

The traditional broadcasting services such as terrestrial, satellite and cable broadcasting have been unidirectional mass media regardless of TV viewer’s preferences. Recently rich media streaming has become possible via the broadband networks. Furthermore, since bidirectional communication is possible, personalcasting such as personalized streaming service has been emerging by taking into account the user’s preference on content genres, viewing times and actors/actresses etc. Accordingly personal media becomes an important means for content provision service in addition to the traditional broadcasting service as mass media. In this paper, we introduce a user profile reasoning method for TV viewers. The user profile reasoning is made in terms of genre preference and TV viewing times for TV viewer’s groups in different genders and ages. For user profiling reasoning, the TV viewing history data is used to train the proposed user profiling reasoning algorithm which allows for target advertisement for different age/gender groups. To show the effectiveness of our proposed user profile reasoning method, we present plenty of the experimental results by using real TV usage history.     

Admission control for media on demand services

Admission control software is used to make accept or deny decisions about incoming service requests to avoid overload. Existing media streaming software includes only limited support for admission control by allowing for predefined static rules. Such rules limit for example the number of requests that are allowed to enter the system during a certain time or define thresholds concerning the utilization level of a single resource such as network bandwidth. In media streaming applications, however, the bottleneck resource (CPU, Disk I/O, network bandwidth, etc.) might change over time depending on the current demand for different types of audio or video files. This paper proposes a model for adaptive admission control in the presence of multiple scarce resources. Opportunity costs for a service request are determined at the moment of an incoming request and compared to the revenue of a request in order to make an accept/deny decision. Opportunity costs are based on resource utilization, service resource requirements, expected future demand for services, and the revenue per accepted service. The model allows rejection of service requests early to reserve capacity required to perform future service requests with higher revenues. We describe a number of experiments to illustrate the benefits of adaptive admission control models over static admission control rules.