影响VoD服务器I/O性能的关键因素

在讨论了基于网络视频点系统模型和通用服务器体系结构的基础上，主要分析了影响视频点播服务器性能I／O能力的几个关键因素，对存储设备的吞吐量，PCI总线速率，SCSI通道的速率和网卡的传输速度等对服务器I／O性能的影响进行了较全面，深入的分析，最后提高一种利用服务器集群的方式提高VoD系统I／O能力的方法。     

VOD服务器性能及服务方式研究

在视频点播领域的关键性挑战就是以合理经济的成本为成千上万的潜在用户提供交互点播服务。为寻求这个问题的解决方案，对VOD服务器性能及服务方式选择进行了深入的研究。介绍了视频点播系统的几种分类方式，对影响视频点播服务器性能的关键要素和视频点播系统提供点播服务的方式进行了较全面和深入的分析，在此基础上提出和讨论了一些提高服务器性能和服务质量的实用策略和技术。     

VOD服务器设计的支撑技术

本文从连续媒体数据分布、磁盘调度和回取控制、缓存控制、允许控制与内资源分配、带平滑、可扩展性和交互等多方面对视频服务器性能影响很大的支撑技术进行了讨论。     

视频服务器性能测试研究

视频点播是能向用户提供视频信息服务的应用系统,视频服务器是其中最关键的部分。随着技术的发展,用户对视频服务器的性能要求越来越高。但由于其实现方式上的差异,研究者并没有对视频服务器性能评价指标和测试方法形成共识。对此,文章提出并分析了视频服务器的各种评价指标,并据此给出了一个测试软件的实现方案。     

VOD视频服务器中的视频流调度策略

介绍了视频服务器中的几种视频流调度策略，并在此基础上给出了一种新的调度策略。     

一种小区VOD系统方案设计

视频点播系统是多媒体应用的一个重要发展方向，针对这种现状阐述了在一个中等规模的小区内建立一套视频点播系统的设计方案，包括系统总体设计、系统网络设计和系统功能设计、软件设计等，并对系统的可扩展性做了一定的说明。     

一种基于节的视频服务器允许接纳控制算法

提出了一种基于“服务器节”的支持压缩多媒体流的服务器中CPU、磁盘、网络和内存等资源管理的方法和允许接纳控制算法。“服务器节”概念定义了一组客户视频服务特性,如播放、快进、慢进和暂停等,并且确定了视频服务所需资源的分配参。一个“服务器节”包括视频服务器、磁盘设备、网络设备和允许接纳控制。它不但能优化使用单个资源,对于给定系统支持最大数量的客户端,保证其服务质量（QoS),而且其允许接纳控制算法能根据系统所有资源的状况,在不影响原有的视频服务基础上,确定对客户端新提出的视频服务是否接受。     

一种VoD系统视频服务器的设计与实现

论述了一种基于大容量IDE硬盘的分布式VoD系统的视频服务器的存储设计、硬件配置、数据管理模式和实现方法。     

可扩展的VOD服务器系统

提出了分布式可扩展的VOD系统结构，扩展性的研究能够提供更多的并发流服务。从系统结构及工作流程、基于CORBA的通讯、负载均衡及存储技术等方面论述了系统的扩展性。测试结果表明，该系统可以适应不同规模的VOD应用。     

Flexible Strategies for Disk Scheduling in Multimedia Presentation Servers

Multimedia presentations (e.g., lectures, digital libraries) normally include discrete media objects such as text and images along with continuous media objects such as video and audio. Objects composing a multimedia presentation need to be delivered based on the temporal relationships specified by the author(s). Hence, even discrete media objects (that do not normally have any real-time characteristics) have temporal constraints on their presentations. Composition of multimedia presentations may be light (without any accompanying video or large multimedia data) or heavy (accompanied by video for the entire presentation duration). The varying nature of the composition of multimedia presentations provides some flexibility for scheduling their retrieval. In this paper, we present a min-max skip round disk scheduling strategy that can admit multimedia presentations in a flexible manner depending on their composition. We also outline strategies for storage of multimedia presentations on an array of disks as well as on multi-zone recording disks.Emilda Sindhu received the B.Tech degree in Electrical & Electronics from University of Calicut, India, in 1995 and the M.S. degree in Computer Science in 2003 from National University of Singapore. This paper comprises part of her master thesis work. She is presently employed as Senior Research Officer at the A-star Institute of High Performance Computing (IHPC), Singapore. Her current research interests include distributed computing particulary Grid computing. She is involved in the development of tools and components for distributed computing applications.Lillykutty Jacob obtained her B.Sc (Engg.) degree in electronics and communication from the Kerala University, India, in 1983, M.Tech. degree in electrical engineering (communication) from the Indian Institute of Technology at Madras in 1985, and PhD degree in electrical communication engineering from the Indian Institute of Science, in 1993. She was with the department of computer science, Korea Advanced Institute of Science and Technology, S. Korea, during 1996–97, for post doctoral research, and with the department of Computer Science, National University of Singapore, during 1998–2003, as a visiting faculty. Since 1985 she has been with the National Institute of Technology at Calicut, India, where she is currently a professor. Her research interests include wireless networks, QoS issues, and performance analysis.Ovidiu Daescu received the B.S. in computer science and automation from the Technical Military Academy, Bucharest, Romania, in 1991, and the M.S. and Ph.D. degrees from the University of Notre Dame, in 1997 and 2000. He is currently an Assistant Professor in the Department of Computer Science, University of Texas at Dallas. His research interests are in algorithm design, computational geometry and geometric optimization.B. Prabhakaran is currently with the Department of Computer Science, University of Texas at Dallas. Dr. B. Prabhakaran has been working in the area of multimedia systems: multimedia databases, authoring & presentation, resource management, and scalable web-based multimedia presentation servers. He has published several research papers in prestigious conferences and journals in this area.Dr. Prabhakaran received the NSF CAREER Award FY 2003 for his proposal on Animation Databases. Dr. Prabhakaran has served as an Associate Chair of the ACM Multimedia2003 (November 2003, California), ACM MM 2000 (November 2000, Los Angeles), and ACM Multimedia99 conference (Florida, November 1999). He has served as guest-editor (special issue on Multimedia Authoring and Presentation) for ACM Multimedia Systems journal. He is also serving on the editorial board of Multimedia Tools and Applications journal, Kluwer Academic Publishers. He has also served as program committee member on several multimedia conferences and workshops. Dr. Prabhakaran has presented tutorials in several conferences on topics such as network resource management, adaptive multimedia presentations, and scalable multimedia servers.B. Prabhakaran has served as a visiting research faculty with the Department of Computer Science, University of Maryland, College Park. He also served as a faculty in the Department of Computer Science, National University of Singapore as well as in the Indian Institute of Technology, Madras, India.     

媒体服务中流式拷贝性能分析

随着网络带宽的进一步提高,视频点播的瓶颈基本卡在视频服务器端。文章提供的服务器端的流式拷贝,能进一步提高整个系统的服务能力。文章对流式拷贝的过程进行描述,对其中的数学模型进行分析,并与没有流式拷贝的系统进行比较分析。     

Semantic Based Prefetching in News-on-Demand Video Servers

In video databases, a video document has two abstractions. The high level abstraction corresponds to the view in which the contents of that video document are seen by end users, and the low level abstraction corresponds to the physical organization of that video document. Due to the huge size of continuous data, reducing I/O has become a key issue. The latter has been mostly addressed by developing appropriate buffering techniques. In addition, prefetching techniques play a major role to meet the video data requirements. In this paper, we propose a novel prefetching strategy based not only on run-time information (objects access frequencies for example) but also on knowledge about clips structures. The proposed technique merges the two views of a video document to trigger prefetching at the video server level. Simulation experiments for a News-on-Demand application performed on different request scenarios show an improvement of about 18% in the buffer hit-rate with respect, first to the available buffer size and second to the request arrival rate.     

一种基于动态阈值的简化接纳控制策略

在线多媒体业务中,主机和网络瓶颈限制了系统能提供的最大服务量。如何保证用户的服务质量,对不同服务类的请求进行接纳控制,从而使系统获得最大的收益成为关注的焦点。该文分析比较了原有接纳控制机制,提出了一种新的简化的基于动态阈值的策略,能够在保持接纳灵活性的同时保证高级用户的优先性。理论分析和模拟仿真表明,该策略相对于以往几种接纳策略具有一定优势,且这种优势随着高级服务密度的增大及其收益率的提高而越发明显。     

浅析高校多媒体教学的影响因素

随着网络信息技术的飞速发展,多媒体技术已被广泛应用于教育教学中。多媒体是一种集图像、音乐、视频、文字于一体的设备,能够直观地展现课堂内容,将复杂的问题简单化,为学生带来视觉、听觉上的刺激,进而提升教学水平。然而,如何有效地开展高校多媒体教学是当前急需解决的问题。简要分析了高校多媒体教学的影响因素,探讨了提升高校多媒体教学水平的主要途径。     

Web服务器群的QoS确保及其接纳控制研究

WWW访问的爆炸性发展正是Internet成功的重要原因，然而目前的Web服务器却缺乏相应的QoS机制，导致在过载时造成巨大的经济损失。一个提供多类服务的多服务器Web平台的服务质量确保体系被提出来，它以服务响应延迟为核心度量标准，将同一类服务抽象为一台虚拟服务器，并以该度量黏合起系统的各个组件．同时据此提出了一个动态自适应的服务接纳算法(DASAC)．测试表明，即使经历严重的过载与业务突发，也能保证用户感知的服务质量．     

宽带移动多媒体通信的关键技术

移动宽带视频广播,在电信领域的应用就是宽带移动多媒体通信;在广播电视领域的应用就是数字电视的地面广播。该文介绍了宽带移动多媒体通信的关键技术,同时阐述了各种技术的优缺点。     

Efficient Algorithms for Slot-Scheduling and Cycle-Scheduling of Video Streams on Clustered Video Servers

The granularity of scheduling video streams can be categorized as cycle-scheduling and slot-scheduling where a time cycle is further divided into time slots. To avoid resource conflict and thereby increase throughput of clustered video servers, slot-scheduling using conflict-free scheduling and especially cycle-scheduling using full-duplex scheduling and ordered scheduling are presented in the paper. Also, the analysis of the pros and cons of applying slot-scheduling and cycle-scheduling on clustered video servers are discussed.     

Columbia's VoD and Multimedia Research Testbed with Heterogeneous Network Support

This paper reports our progress in developing an advanced video-on-demand (VoD) testbed, which will be used to accommodate various multimedia research and applications such as Electronic News on Demand, Columbia's Video Course Network, and Digital Libraries. The testbed supports delivery of MPEG-2 audio/video stored as transport streams over various types of networks, e.g., ATM, Ethernet, and wireless. Both software and hardware video encoders/decoders are used in the testbed. A real-time video pump and a distributed application control protocol (MPEG-2's DSM-CC) have been incorporated. Hardware decoders and set-tops are being used to test wide-area video interoperability. Our VoD testbed also provides an advanced platform for implementing proof-of-concept prototypes of related research. Our current research focus covers video transmission with heterogeneous quality-of-service (QoS) provision, variable bitrate (VBR) traffic modeling, VBR server scheduling, video over Internet, and video transmission over IP-ATM hybrid networks. An important aim is to enhance interoperability. Accommodation of practical multimedia applications and interoperability testing with external VoD systems has also been undertaken.     

Adaptive QoS Control Based on Benefit Optimization for Video Servers Providing Differentiated Services

We propose and analyze quality of service (QoS) control algorithms for video servers designed to provide differentiated video streaming services. The design concepts are based on resource reservation and benefit optimization so that resources are reserved dynamically and adaptively for different QoS levels in response to the changing workload of the system, with the objective of maximizing the benefit throughput obtainable by the system. We analyze the benefit throughput obtainable by the system for a baseline algorithm for which the QoS levels of admitted users are not changed during the service lifetime and a greedy algorithm that may raise QoS levels of admitted users due to resources being free from departure events. We validate the design of these two QoS control algorithms via a detailed simulation study.