分布存储媒体传输的同步算法

分布多媒体数据库（ＤＭＤＢ）和分布多媒体信息系统（ＤＭＩＳ）的一个重要需求是多媒体同步传输．文中先分析了在ＤＭＤＢ和ＤＩＭＳ中多媒体同步传输的特点和要求，然后提出了一个能满足这些要求的同步传输方案．在这个方案中，多媒体同步关系是用动态同步Ｐｅｔｒｉ网（ＤＳＰＮ）来显式描述的；通过文中给出的同步传输算式和同步发送算法，可以在ＤＳＰＮ模型的基础上产生同步传输调度方案；同时接收端能根据实际通信状况和多媒体的同步要求，对来自多个服务器的多媒体对象进行动态同步控制．     

图书馆多媒体信息同步传输管理方案的研究

文章研究了分步式多媒体信息系统同步传输管理方案,给出了传输过程中多媒体对象所必须遵循的时间约束基本要求,有界缓冲区大小的设置方法,延时抖动的估计方法,并在实际中得到了验证。为网络环境中多媒体对象同步传输进行了有益的探索。     

数字化多媒体信息收集系统的分析与设计

针对传统模拟声像信息收集系统存在的缺点 ,本文提出了一种数字化多媒体信息收集系统 ,并且详细地论述了该系统的系统设计、组网方案及相应的应用软件设计等。这种数字化多媒体信息收集系统不但大大提高了原始多媒体素材的保存质量和保存寿命 ,而且使得多媒体信息利于编辑 ,便于网上传输和点播。     

基于WEB航海类特色资源库的建设

随着多媒体技术和网络技术在高校图书馆中的全面应用,数字化的实体馆藏以及网络化的虚拟馆藏等都构成数字图书馆馆藏发展的完整内客,开发高质量多媒体教学资源库已成为高校图书馆数字化建设的迫切需要,图书馆多媒体资源库建设和服务是现代图书馆一种具有代表性的典型内容,因此本文着重描述了我校圈书馆航海类圈书多媒体资源库的实现过程以及它所能达到的功能。     

基于CMMB系统的同步设计与实现

同步实现对于OFDM基带接收系统而言至关重要,对于面向移动多媒体的基带芯片设计,同步的性能和低功耗设计更是很大的挑战。结合中国移动多媒体广播系统(CMMB)帧结构、调制及其传输信道的特征,提出了适用于多径衰落信道、高载波频偏环境下的OFDM系统时间和载波频率同步方案,并在硬件实现中从算法优化、硬件构架设计两个方面进一步降低同步功耗。     

Internet上数字化图书馆的设计及实现

网络上的数字化图书馆是图书馆自动化的高级阶段,是当前图书馆和情报界研究的热点,也是Internet和信息科学研究的热点。数字化图书馆的关键技术是多媒体信息的数字化,图像、声音、文本等多媒体介质的检索技术及超媒体信息的存储、管理及检索技术,数字化文献的版权保护问题及Web服务器与多媒体数据库的接口问题。 网络上的数字化图书馆是以多媒体数据库为基础的,发展的趋势是超媒体。超媒体是在超文本和多媒体发展到一定阶段相互结合的产物。它包括了两者的所有特     

基于分布式系统实现时钟同步的统计平均算法

讨论了分布式系统中时钟同步的系统模型,远端时钟读取方法以及双向通信传输过程,给出了3种不同的时钟同步方案,同时,对基于多次同步消息的冗余传输,提出了新的基于统计平均的时钟同步算法。通过多步时间传输协议,在较短同步周期内对时钟进行同步。     

医院数字化信息系统的安全问题探讨

随着网络信息的迅猛发展,医院的数字化信息系统安全也搭上了这辆快车,它主要体现在便于传输电子信息和数字化以及多媒体存储转换等信息技术的应用。本文是针对目前医院数字化信息系统的安全问题进行了探讨,并提出了解决的办法     

多媒体阅览室

多媒体阅览室是为广大读者提供阅读多媒体电子书刊、检索多媒体信息以及开展其它多媒体娱乐活动的场所。随着多媒体出版物的日益增多以及网上多媒体信息资源的日益丰富,开发面向社会、面向大众的普及型多媒体阅览室已不再遥远。在学校、文化馆或街道等场所创建具有一定规模和水平的多媒体阅览室,可拓宽服务,丰富生活。 多媒体阅览室的发展概述 八十年代,由于CD-ROM技术的成熟,使数字化电子出版物融声频、视频、图形、图象和文本为一体成为现实。国外出现的电子图书馆和数字图书馆,就包含有多媒体阅览室。 1990年,谢菲尔德大学图书馆按照大英图书馆研究和     

Intranet上实时多媒体混播技术研究

针对Intranet底层对组播提供的支持并不明确这一问题,提出了一种混播,即组播和单播相结合的实时多媒体传输方案。该方案通过构造分配树,使用其分支结点转发数据的方法,以实现一对多的分布式多媒体传输。文章还对混播技术在实现时遇到的多媒体数据发送、重传、网络拥塞调整以及安全管理等问题作了具体的讨论。     

QoS Management in Educational Digital Library Environments

Advances in multimedia computing technologies offer new approaches to the support of computer-assisted education and training within many application domains. Novel interactive presentation tools can be built to enhance traditional teaching methods with more active learning. Since a variety of user expectations are possible in such an environment, research must address the incorporation of these factors into presentation tools. During an interactive learning/training process, presentation tools must be able to handle various types of delays. A flexibly adjustable quality of service (QoS) should thus be supported. In this paper, we investigate a framework and systematic strategies for supporting the continuous and synchronized retrieval and presentation of multimedia data streams in a client/server distributed multimedia environment for educational digital libraries. Specifically, we establish a practical framework for specifying multimedia objects, tasks, schedules, and synchronization constraints between media streams. We identify the QoS parameters critical to the support of multimedia presentations for learning and training activities. Based on the proposed framework and QoS specifications, we develop presentation scheduling and buffer management strategies which can enforce the specified QoS requirements in an educational digital library environment.     

A quality-of-service specification for multimedia presentations

The bandwidth limitations of multimedia systems force trade-offs between presentation-data fidelity and real-time performance. For example, digital video is commonly encoded with lossy compression to reduce bandwidth, and frames may be skipped during playback to maintain synchronization. These trade-offs depend on device performance and physical data representations that are hidden by a database system. If a multimedia database is to support digital video and other continuous media data types, we argue that the database should provide a quality-of-service (QOS) interface to allow application control of presentation timing and information-loss trade-offs. This paper proposes a data model for continuous media that preserves device and physical data independence. We show how to define formal QOS constraints from a specification of ideal presentation outputs. Our definition enables meaningful requests for endto-end service guarantees, while leaving the database system free to optimize resource management. We propose one set of QOS parameters that constitute a complete model for presentation error, and we show how this error model extends the opportunities for resource optimization.     

数字图书馆多媒体信息传输服务质量管理方案的研究

本文研究了分步式多媒体信息系统QOS管理方案,给出了该系统QOS管理基本要求 ,并针对数字化图书馆海量分布多媒体信息资源的特点,给出了其QOS管理的基本功能以及 具体实现,并在局域网环境下对该方案进行了测试．     

A CORBA Based QOS Support for Distributed Multimedia Applications

Advance object oriented computing platform such as the Common Object Request Broker Architecture (CORBA) provides a conducive and standardized framework for the development of distributed applications. Most of the off-the-shelf CORBA are implemented over legacy network transports and distributed processing platforms such as TCP/IP and RPC. They are not suitable for real-time applications due to their high processing overheads, and lack of features and mechanisms in supporting quality of service both at the network level and at the end-host level. To overcome this limitation we have designed and implemented a CORBA-based Real Time Stream Service (RTSS) that allows real-time streams to be managed through the CORBA channel but by-passing the heavy CORBA protocol stacks. RTSS aims to achieve an integrated QOS framework that incorporates both host scheduling and end-to-end network-level QOS to better support the processing of distributed multimedia applications over ATM networks. For host scheduling, a novel scheme of frequency-based scheduling mechanism has been proposed to cope with dynamic CPU load condition. The scheme has been implemented for a stand-alone host and will be extended to the networked environment. At the network-level QOS, RTSS provides object-oriented application programming interfaces (APIs) which guarantee end-to-end QOS when operating directly over ATM adaptation layers. The benefits of RTSS for the development of real-time multimedia distributed applications are demonstrated through a number of experiments.     

Dynamic playout scheduling algorithms for continuous multimedia streams

In this paper, we investigate a playout scheduling framework for supporting the continuous and synchronized presentations of multimedia streams in a distributed multimedia presentation system. We assume a situation in which the server and network transmissions provide sufficient support for the delivery of media objects. In this context, major issues regarding the enforcement of the smooth presentation of multimedia streams at client sites must be addressed to deal with rate variance of stream presentations and delay variance of networks. We develop various playout-scheduling algorithms that are adaptable to quality-of-service parameters. The proposed algorithms permit the local adjustment of unsynchronized presentations by gradually accelerating or retarding presentation components, rather than abruptly skipping or pausing the presentation materials. A comprehensive experimental analysis of the proposed algorithms demonstrates that our algorithms can effectively avoid playout gaps (or hiccups) in the presentations. This scheduling framework can be readily used to support customized multimedia presentations.     

Quality-of-service management for multimedia streams with fixed arrival periods and variable frame sizes

Some types of multimedia streams, like compressed video, transmit frames of various sizes at fixed periodic instants. For such variable bit-rate streams, there is a trade-off between the transmission bandwidth reserved (and potentially unused) and the queueing delays observed. Moreover, the calculation of quality-of-service (QOS) guarantees is not trivial. The purpose of this paper is twofold. First, we present a QOS management scheme that maps variable bit-rate streams to a simple, periodic traffic model and thus allows for the estimation of delay bounds. The approach also includes a tuning parameter that explicitly controls the trade-off between reserved bandwidth and delay. Second, the scheme is applied to some real-world scenarios. Its validity is proven and hints for the practical control of the trade-off are derived.     

Receiver-initiated communication with ST-II

As part of its work on the Heidelberg Transport System (HeiTS) for multimedia communication, the IBM European Networking Center (ENC) has implemented the Experimental Internet Stream Protocol, Version 2 (ST-II). ST-II is a connection-oriented internetworking protocol for multiple-destination communication of real-time data such as digital audio and video. Although ST-II fits well into typical multimedia application scenarios, some functions are still missing No mechanisms are provided for receiver-initiated communication, allowing receivers to join streams, specify their quality of service (QOS) requirements, or initiate stream establishment and resource reservation. In this paper, we present some extensions to tile protocol that make it fulfill the receivers' needs move adequately. Our approach allows intermediate nodes to execute stream management functions on behalf of the sender. This way, the protocol scales better with the number of receivers per stream, as the origin does not need to track every target.     

IP Muticast在网络多媒体教学系统中的应用研究

提出了独立于网络系统平台的基于IP组播的多媒体网络教室的纯软件解决方案,设计并实现了一个基于IP组播的纯软件的多媒体网络教学系统,该系统能保证传输流的服务质量,可以有效地拓展会话节点的规模。     

Scheduling multimedia presentations in educational digital libraries

An educational digital library is a specialized digital library containing instructional materials, such as class lectures, seminar presentations, and various training materials. These materials consist of a combination of audio, video, and image data. In such an environment, basic parts of multimedia data are usually stored in databases and sophisticated multimedia presentations may be assembled to generate various presentations. In this paper, we investigate a theory of the scheduling strategies for supporting the synchronized presentations of multimedia streams which is applicable to educational digital libraries. This scheduling theory includes the specification and representation of synchronization on media streams, the realization of appropriate synchronization granularity, and the scheduling principles for the presentations of multimedia streams. This investigation formulates criteria for specifying and scheduling the skipping/pausing of media streams with asynchronous presentations when various delays occur. Adaptability to various quality-of-service requirements is supported in the scheduling strategies. Various synchronization mechanisms at both client and server sides are proposed to implement the scheduling theory. Experimental analysis is conducted using instructional materials.