IP组播技术及其在视频监控系统中的应用

IP组播在IP网络中实现了多点通信模型,促进了视频点播、音视频会议和数据分发等多点通信业务在互联网上的发展,是互联网络发展的一个重要方向。采用IP组播技术实现监控视频的多点传输,可以大大节省网络带宽资源,提高数据传送的效率。本文对IP组播技术和其在视频监控系统中的应用作了介绍。给出了组播技术在视频传输系统中的设计思想与实现方法。运行结果表明,方案合理,运行可靠。     

RSVP协议在视频点播中的应用研究

IP网络环境下视频传输技术是很多新型网络应用 (如视频点播、视频会议、视频监控等 )的关键技术之一。研究了资源预留协议RSVP在视频点播系统中视频传输的应用 ,讨论和分析了如何利用资源预留协议解决视频点播系统中视频传输的服务质量问题。     

电信级视频点播系统的设计与实现

视频点播服务是一种新的信息服务。作为信息服务运营商,电信需要构建电信级的视频点播系统以便有效提供电信级视频点播服务。针对电信级视频点播服务的设计需求,本文提出了一个电信级视频点播层次型分布式系统架构,并在该架构下,整合视频服务子系统、容错子系统、节目管理子系统、节目分发子系统、节目采编子系统、用户认证计费系统和网管子系统等七大功能系统,完整地实现了一个电信级视频点播系统,最终实现了城域范围内的视频点播服务。     

动态段阈值机制在P2Cast VoD系统中的应用

本文对一种新型的视频点播系统P2Cast视频点播系统的关键技术进行了研究,针对段阈值在系统的可扩展性方面以及视频服务质量方面所起的重要作用,结合补丁流算法和客户节点的请求速率提出了一种嵌入动态调节段闲值机制的BF改进算法。该算法在一定程度上提高了P2Cast视频点播系统的性能。     

IBM xSerier345 SCSI硬盘磁盘阵列的实现

本文简要介绍了磁盘陈列技术原理和实践运用价值，并详细介绍如何在IBM xSerier345 SCSI硬盘上实现磁盘陈列的过程和方-击。说明利用RAID技术能提高磁盘存取速度、提高系统的客错能力。对那些网络管理员或系统维护员在存储设备的建设和维护过程中有很好的实践参考价值。     

优化的存储模式——VBR视频安置在MS磁盘组上

研究了大量VBR视频在MZ磁盘组上的安置和接纳计算方法，基于视频的VBR特性，视频的流行性及MZ磁盘的特性，提出了一个优化的存储模式及相应的接纳算法，和其它现存算法相比，结果显它能支持更多的流数，在作品流行性变化的情况下更好的适应能力。     

DPVoD:基于P2P的视频点播体系结构

可扩展性和可靠性是视频点播系统大规模应用的关键,提出了一种P2P点播系统结构DPVoD.系统基于应用层组播,用户以订制的缓存为其他节点提供服务,并形成相对独立的共享并发流组播树,组播树之问根据拥有的视频数据的重合程度而建立不同的组邻居关系,以此为基础,采用多种机制来提高系统性能:组协同工作、父亲点选择策略、状态控制协议和失效恢复等.定义并分析了可能对系统性能有严重影响的结尾雪崩问题并提出解决方案.对系统基本性能进行了理论分析.仿真结果表明,在静态和动态环境中,DPVoD系统的并发流占用数和利用率、可靠性等性能均优于类似系统.     

PostgreSQL数据库预取算法研究

减少磁盘的存取时间是提高数据库性能的关键.本文讨论了PostgreSQL数据库顺序存取的特性,提出了一种PostgreSQL中顺序预取数据块的算法,预取的数据块数目可根据当前存取块之前的顺序存取情况作自适应调整.实验结果表明,该算法能有效地提高磁盘块的平均存取速度.     

视频点播系统中基于流行度的MBGC策略

视频节目的调度策略是视频点播系统中有效使用存储资源和网络资源的关键技术,优化的节目调度和管理可以极大的提高视频服务器的性能。根据流行度来划分视频节目的优先级,提出了一种视频节目调度算法——可移动边界保护信道法(MBGC),并设计了一个二维的Markov链对算法的性能进行了理论上的分析,最后的数值分析结果表明,提出的算法提高了系统的性能。     

IBM xSerier345 SCSI硬盘磁盘适阵列的实现

本文简要介绍了磁盘陈列技术原理和实践运用价值,并详细介绍如何在IBM xSerier345 SCSI硬盘上实现磁盘陈列的过程和方法.说明利用RAID技术能提高磁盘存取速度、提高系统的容错能力.对那些网络管理员或系统维护员在存储设备的建设和维护过程中有很好的实践参考价值.     

一种克服磁盘存取受限的视频点播机制

1 引言在视频服务器中,大量的待点播视频流数据以分级存储模式被加以组织,其中点播概率小的节目被存放在低速廉价的光盘库中作为非在线视频(off-line)。为保证视频的播送质量,非在线视频必须先存放到硬盘缓冲区中才能被播放。进一步考虑到网络传输性能因素,将视频服务器按层次化结构进行组织,将待点播的视频数据靠近用户存放,保证缓存的数据     

Dynamic Buffer Management for Near Video-On-Demand Systems

Advances in networking and storage technology have made it possible to deliver on-demand services over networks such as the emerging video-on-demand (VOD) applications. A variety of studies have been focused on designing a video server suitable for VOD applications. However, the number of concurrent on-demand services supported by the server is often limited by the I/O bandwidth of the storage systems. This paper describes a discrete buffer sharing model which uses batching and buffer sharing techniques in video servers to support a large number of VOD services. Two operations, splitting and merging, enable the model to fully utilize system resources such as buffers and disk bandwidths. Moreover, this paper also introduces the concept of imprecise video viewing which assumes that a limited amount of quality loss is acceptable during video playback. Based upon this assumption, three shrinking strategies are explored to reduce buffer requirements. Finally, the results of experiments show that our methods perform better than traditional buffer management techniques for VOD systems.     

视频服务器存储子系统的I/O优化

视频服务器存储子系统的I／O性能决定了视频服务器的总体性能。本文提出的一种新的实时磁盘调度算法（LLF－Window)能有效地服务各种编码格式的视频流，并对传统的SCSI总线不均衡调度机制进行了改造，实验结果表明，新的磁盘调度算法和改造后的SCSI总线调度机制有效地改进了视频服务器存储子系统的I／O性能，保证了视频流的连续播放。     

基于I/O空闲率的硬盘功耗建模与评估方法研究

存储设备的功耗在整个计算机系统尤其是数据中心所占的比例已经越来越大。要进行硬盘功耗优化,在缺少硬件直接测量硬盘功耗的情况下就需要对硬盘功耗进行建模。现代操作系统通过文件系统层进行硬盘I/O操作管理,并提供实时监控数据。通过对EXT2、EXT4和NILFS2等常用文件系统的硬盘I/O过程进行实验分析,发现不同的文件系统对硬盘功耗具有不同的影响,为了刻画这种差异性,提出基于I/O空闲率的硬盘功耗建模与评估方法。同时使用I/O空闲率来指导硬盘进行功耗优化,将视频播放器的I/O空闲率由4.79%提高到96.55%,硬盘的功耗降低45.28%。     

Operating system support for the management of hard real-time disk traffic

Emerging applications like C³I systems, real-time databases, data acquisition systems and multimedia servers require access to secondary storage devices under timing constraints. In this paper, we focus on operating system support needed for managing real-time disk traffic with hard deadlines. We present the design and implementation of a preemptive deadline-driven disk I/O subsystem suitable for real-time disk traffic management. Preemptibility is achieved with a granularity that is automatically controlled by the I/O subsystem according to current workload and filesystem data layout. An admission control test checks the current resource availability for a given workload. We show that contiguous layout is necessary to maintain hard real-time guarantees and a reasonable level of disk throughput. Finally, we show how buffering can be used to obtain utilization factors close to the maximum disk bandwidth possible.     

影响多媒体服务器性能的关键因素研究

在构建大规模视频服务系统时 ,基于层次型多服务器群的体系结构在吞吐率、可扩展性、经济性等方面都有其突出的优势 ,尤其适合于在因特网上的应用 .但是 ,要充分发挥和提高视频服务系统的性能 ,还要针对一些主要的瓶颈(如服务器磁盘 I/ O带宽与网络带宽 ) ,解决好一系列的问题 .本文分析了影响多媒体视频服务器性能的一些主要因素 ,如视频服务器的体系结构、服务器与客户端之间的数据传送方式、媒体数据在视频服务器存储子系统中的分布与放置方式、对磁盘访问请求的调度、单服务器中的缓存及多服务器间协同缓存的管理、接入控制策略、流调度策略等 ,这些因素对视频服务器的性能与吞吐率有着极大的影响 .本文还介绍了一些适用于大规模视频服务系统的性能优化技术 ,如广播、批处理等流调度策略 .在构建视频服务器系统时 ,只有综合考虑这些因素 ,才能真正提高服务器乃至整个视频服务系统的吞吐率 ,并较好地满足客户的 Qo S要求     

Performance analysis of advanced I/O architectures for PC-based video servers

In the personal computing and workstation environments, more and more I/O adapters are becoming complete functional subsystems that are intelligent enough to handle I/O operations on their own without much intervention from the host processor. The IBM subsystem control block (SCB) architecture has been defined to enhance the potential of these intelligent adapters by defining services and conventions that deliver command information and data to and from the adapters. In recent years, a new storage architecture, the redundant array of independent disks (RAID), has been quickly gaining acceptance in the world of computing. In this paper, we discuss and present a performance analysis of the SCB architecture and disk array technology in typical video server environments. In particular, we would like to see whether a disk array can outperform a group of disks (of the same type, the same data capacity, and same cost) operating independently (not in parallel as in a disk array) in a video server environment where most disk I/O operations are large sequential reads.     

I/O issues in a multimedia system

In future computer system design, I/O systems will have to support continuous media such as video and audio, whose system demands are different from those of data such as text. Multimedia computing requires us to focus on designing I/O systems that can handle real-time demands. Video- and audio-stream playback and teleconferencing are real-time applications with different I/O demands. We primarily consider playback applications which require guaranteed real-time I/O throughput. In a multimedia server, different service phases of a real-time request are disk, small computer systems interface (SCSI) bus, and processor scheduling. Additional service might be needed if the request must be satisfied across a local area network. We restrict ourselves to the support provided at the server, with special emphasis on two service phases: disk scheduling and SCSI bus contention. When requests have to be satisfied within deadlines, traditional real-time systems use scheduling algorithms such as earliest deadline first (EDF) and least slack time first. However, EDF makes the assumption that disks are preemptable, and the seek-time overheads of its strict real-time scheduling result in poor disk utilization. We can provide the constant data rate necessary for real-time requests in various ways that require trade-offs. We analyze how trade-offs that involve buffer space affect the performance of scheduling policies. We also show that deferred deadlines, which increase buffer requirements, improve system performance significantly     

Issues in the design of a storage server for video-on-demand

We examine issues related to the design of a storage server for video-on-demand (VOD) applications. The storage medium considered is magnetic disks or arrays of disks. We investigate disk scheduling policies, buffer management policies and I/O bus protocol issues. We derive the number of sessions that can be supported from a single disk or an array of disks and determine the amount of buffering required to support a given number of users. Furthermore, we propose a scheduling mechanism for disk accesses that significantly lowers the buffer-size requirements in the case of disk arrays. The buffer size required under the proposed scheme is independent of the number of disks in the array. This property allows for striping video content over a large number of disks to achieve higher concurrency in access to a particular video object. This enables the server to satisfy hundreds of independent requests to the same video object or to hundreds of different objects while storing only one copy of each video object. The reliability implications of striping content over a large number of disks are addressed and two solutions are proposed. Finally, we examine various policies for dealing with disk thermal calibration and the placement of videos on disks and disk arrays.     

Design and Implementation of the Stony Brook Video Server

The system architecture of the Stony Brook Video Server (SBVS), which guarantees end-to-end real-time video playback in a client-server setting, is presented. SBVS employs a real-time network access protocol, RETHER, to use existing Ethernet hardware as the underlying communications media. The video server tightly integrates the bandwidth guarantee mechanisms for network transport and disk I/O. SBVS's stream-by-stream disk scheduling scheme optimizes the effective disk bandwidth without incurring significant scheduling overhead. To demonstrate the feasibility of the proposed architecture, we have implemented a prototype called SBVS-1, which can support five concurrent MPEG-1 video streams on an Intel 486DX2/EISA PC. To our knowledge, this system is the first video server that provides an end-to-end performance guarantee from the server's disks to the each user's display over standard Ethernet. This paper describes the implementation details of integrating network and I/O bandwidth guarantee mechanisms, and the performance measurements that drive and/or validate our design decisions. © 1997 by John Wiley & Sons, Ltd.