分布式多媒体数据库中连续媒体的同步

在多媒体数据库系统中,多媒体对象的展示显然必不可少,所要展示的媒体可分为三种类型:静态、动态和混合类型。静态类型是指来自不同(或相同)存贮位置,但无时间变化的静态图像、文本等;动态类型是指时间、空间都变化的视频、音频、动画等媒体;混合类型是静态和动态类型的综合,在展示混合和动态类型的媒体时,必须要考虑媒体间以及媒体内部在时间上的同步关系。例如,在同界面上说话者的口形应与其声音保持同步(lip一,ynchroniza-tion),在同一屏幕的不同窗口显示动画时,应保持各窗口的画面在时间上的同步。     

基于SGI的多媒体创作工具的设计与实现

本文针对SGI图形工作站的特点,论述了基于SGI平台的多媒体创作工具AUTHOR的系统构造及其关键技术的实现。在媒体对象的同步中,采用时间流Petri网（TSPN）模型表示媒体数据流的同步、互斥等关系,用该模型结合“自上而下、逐步求精”的软件设计方法,描述了复杂多媒体表示系统中的媒体表示方案。     

基于DirectX的媒体流再现与同步的实现

通过介绍Direct X的DirectDraw和DirectSound技术，给出了基于DirectX对音视频流进行媒体的再现与同步的具体实现，采用以视频帧的时间戳为基准进行同步的时间戳同步机制。本文在远程监控系统中很好地实现了媒体流的高质量播放再现，解决了多媒体流的同步问题。     

基于MPEG-4的多媒体同步模型设计

文中旨在研究基于MPEG4技术的面向对象多媒体同步。所采用的方法是在分析现有多媒体同步模型的基础上，结合MPEG-4系统同步机制和高级同步模型（FlexTime），设计面向对象的多媒体同步模型，以实现MPEG-4中各媒体对象间同步。由此方法设计的层结构同步模型是一种有效可行的多媒体间同步的实现方法。和其它的多媒体间同步方法相比，这种方法在基于对象的多媒体的传输过程中携带较少的时间信息来完成对象间的同步，并且增强了基于对象内容交互的灵活性。     

基于MPEG-4的多媒体同步模型设计

文中旨在研究基于MPEG-4技术的面向对象多媒体同步。所采用的方法是在分析现有多媒体同步模型的基础上,结合MPEG-4系统同步机制和高级同步模型(FlexTime),设计面向对象的多媒体同步模型,以实现MPEG-4中各媒体对象间同步。由此方法设计的层结构同步模型是一种有效可行的多媒体间同步的实现方法。和其它的多媒体间同步方法相比,这种方法在基于对象的多媒体的传输过程中携带较少的时间信息来完成对象间的同步,并且增强了基于对象内容交互的灵活性。     

远程教学直播系统中媒体同步的研究与实现

对于远程教学直播系统这样包含不同媒体流的分布式多媒体应用而言，媒体同步是一项重要内容。利用RTP（实时传输协议）传输机制中的时间戳和序列号信息，提出同步控制算法，实现了流内同步和流间同步。考虑到分组网络带来的延时抖动，算法可以动态地适应网络延时变化，从而保证了分布式环境中媒体同步的服务质量。     

互动多媒体同步机制设计

研究了基于 MPEG-4的面向对象多媒体同步技术。在分析现有多媒体同步技术的基础上，结合 MPEG-4 系统同步机制和高级同步模型(FlexTime)，设计了层结构同步模型，以实现 MPEG-4 中各媒体对象间同步，是一种有效可行的多媒体间同步的实现方法。     

多媒体同步

多媒体同步是分布多媒体应用的一个重要需求。本文从时间相关媒体入手，就多媒体同步的多样性、同步特性、同步服务质量参数、同步时间概念模型以及同步关系的同象和描述等方面予以较全面的分析和阐述。     

PREMO:多媒体同步的标准模型

本文描述了PREMO的基于事件的同步机制,该机制是多媒体表现标准中媒体间同步的核心,是以活动对象间互操作为基础的。分析表明,PREMO的这种同步机制综合了其它各种同步模型,是多媒体表现中实现复杂同步模式的强大工具。     

多媒体同步技术研究

1 引言 多媒体同步表现是多媒体研究和开发应用的关键技术。在多媒体系统中,各种媒体并存,既有视觉方面的文字、图像,又有语音、音乐等听觉信息。各种媒体如何在空间进行组织、时间上如何安排、媒体之间的相互作用如何描述和解释等,都是在表现信息时必须考虑的问题。我们在设计桂林旅游信息咨询系统中也涉及到各种媒体的同步表现问题。例如,在进行景点介绍时既有景点的风景图片,又有文字说明,还伴有语音解说。如何实现三者之间的同步表现就是一个必须解决的     

A spatio-temporal semantic model for multimedia database systemsand multimedia information systems

As more information sources become available in multimedia systems, the development of abstract semantic models for video, audio, text, and image data is becoming very important. An abstract semantic model has two requirements: it should be rich enough to provide a friendly interface of multimedia presentation synchronization schedules to the users and it should be a good programming data structure for implementation in order to control multimedia playback. An abstract semantic model based on an augmented transition network (ATN) is presented. The inputs for ATNs are modeled by multimedia input strings. Multimedia input strings provide an efficient means for iconic indexing of the temporal/spatial relations of media streams and semantic objects. An ATN and its subnetworks are used to represent the appearing sequence of media streams and semantic objects. The arc label is a substring of a multimedia input string. In this design, a presentation is driven by a multimedia input string. Each subnetwork has its own multimedia input string. Database queries relative to text, image, and video can be answered via substring matching at subnetworks. Multimedia browsing allows users the flexibility to select any part of the presentation they prefer to see. This means that the ATN and its subnetworks can be included in multimedia database systems which are controlled by a database management system (DBMS). User interactions and loops are also provided in an ATN. Therefore, ATNs provide three major capabilities: multimedia presentations, temporal/spatial multimedia database searching, and multimedia browsing     

电子图书馆多媒体信息传输服务质量管理的研究

该文在浏览器/服务器环境下建立了一个数字化图书馆多媒体数据流同步传输的管理方案。定义了多媒体对象、任务、同步化传输约束条件以及相应的QOS评价指标,基于上述方案及评价指标,给出了数字化图书馆多媒体流同步传输的控制算法以及相应的实验结果。     

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.     

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 model-based authorware for the construction of distributed multimedia systems

Distributed multimedia systems typically involve a sophisticated user interaction. Further, objects are allocated on physically distributed computing systems, and multimedia data must be transferred across heterogeneous networks in a timely manner. These systems often have complex requirements on a user interaction, quality of service and temporal order among media streams. The design and implementation of these requirements are inherently complex and present an extraordinary design and programming challenge. Generally, these complex requirements cannot be adequately captured using a single model or a design notation. The challenge amounts to (i) identification of multiple, often orthogonal models, each capturing a specific aspect of the requirements, and (ii) provision of an authorware that supports the composition of these models. In this paper, we propose to capture the multimedia requirements in three different models: configuration, user control and presentation, and demonstrate how the composition of these models can be supported by an authorware using the Java and CORBA technologies. The concepts are illustrated using a real-life example based on a virtual city tour application that features distributed controls, collaborative work and multimedia presentations. Various distributed multimedia applications like video phone, video conferencing and distributed presentation have been successfully constructed using the proposed multiple models and authorware. The results are encouraging and the approach can shorten the development of multimedia applications considerably.     

Buffer model and management in distributed multimedia presentation systems

The delivery of continuous and synchronous multimedia data from a database (or file) server to multiple destinations over a network presents new challenges in the area of buffer management. Many factors that were not considered in conventional buffer management must be examined. In this paper, we investigate the principles of buffer model and management for multimedia data presentations in distributed systems. The primary goal is to minimize the response time of multimedia presentations while ensuring that all continuity and synchronization requirements are satisfied. A framework for buffer model and management is introduced. Minimum buffering requirements at both client and server sides to guarantee the continuity and synchrony of the presentation of multimedia data are examined. A prefetching and replacement strategy which satisfies these requirements is then offered. These principles and techniques provide users with the full range of information required to develop a distributed system for multimedia presentations.     

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.     

Meta-Data and Media Management in a Multimedia Interactive Telelearning System

This paper describes the system design and the components of a web-based multimedia interactive Telelearning system (MITS) with emphasis on metadata and media content management mechanisms. Metadata model is defined and exploited in designing the overall architecture to support courseware creating, management, delivery, and learner performance evaluation. Multimedia document architecture is used to describe the media contents which represent the course material. Metadata and media contents are generated, stored, and utilized to facilitate the search and on-demand presentation of learning objects. Learner preference, performance and progress information is maintained by profile database to make courseware presentation adaptable and more interactive. The system provides a multimedia interactive learning environment with easy-to-search and highly reusable learning objects.