一个桌式数据会议系统的原型：多媒体技术的一个新应用

本文介绍一个自行设计和开发的桌式数据会议系统。该会议系统实现于ＵＮＩＸ工作站和ＴＣＰ／ＩＰ网络上，并充分利用了多媒体技术，文中指出了桌式数据会议系统的基本要求和其实现中的技术关键。     

在分组交换环境下建立一个多媒体会议系统的研究

本文讨论了在分组交换环境下建立一个桌面多媒体会议系统的可能性,研究了多媒体会议系统的特点、组成、工作方式及实现,并指出了分组交换在支持多媒体传输方面应解决的几个关键问题。     

Why do users like video?

Three studies of collaborative activity were conducted as part of research in developing multimedia technology to support collaboration. One study surveyed users' opinions of their use of video conference rooms. Users indicated that the availability of the video conference rooms was too limited, audio quality needed improvement, and a shared drawing space was needed. A second study analyzed videotapes of a work group when meeting face-to-face, video conferencing, and phone conferencing. The analyses found that the noticeable audio delay in video conferencing made it difficult for the participants to manage turn-taking and coordinate eye glances. In the third study, a distributed team was observed under three conditions: using their existing collaboration tools, adding a desktop conferencing prototype (audio, video, and shared drawing tool), and subtracting the video capability from the prototype. Qualitative and quantitative data were collected by videotaping the team, interviewing the team members individually, and recording their usage of the phone, electronic mail, face-to-face meetings, and desktop conferencing. The team's use of the desktop conferencing prototype dropped significantly when the video capability was removed. Analysis of the videotape data showed how the video channel was used to help mediate their interaction and convey visual information. Desktop conferencing apparently reduced e-mail usage and was perceived to reduce the number of shorter, two-person, face-to-face meetings.     

Conferencing and collaborative computing

As integrated services have become available to the desktop, users have embraced new modes of interaction, such as multimedia conferencing and collaborative computing. In this paper, we provide a survey of past and present research that has influenced this application area, and describe research directions for the future.     

The Personal Presence System: a wide-area network resource for the real-time composition of multipoint multimedia communications

The Personal Presence System (PPS) is an experimental research prototype platform to support advanced broadband applications, including multimedia conferencing and distance learning. It supports the user's presentation control of advanced network elements (multimedia bridges). The multimedia bridge provides for a single contact point per user, who receives only one combined video stream, which minimizes access bandwidth. This architecture solves the -squared transmission problem of multipoint video conferencing and makes customer terminal equipment simpler and cheaper than high-end desktop workstations. The PPS provides each user with flexible presentation control of a feature-rich video bridge. The PPS also supports advanced features such as object extraction and multimedia object associations.     

以太网上的多媒体传输

为了在以太网上有效地传输多媒体信息，本文提出了一种位于传输层的基于动态优先级调度的令牌传递策略，对发向以太网的数据包进行控制，避免碰撞的发生，保证数据的定时发送。     

H.323标准及其在Internet上的应用

Ｈ．３２３ 系列标准是基于信包交换网络的多媒体会议标准,它使用ＴＣＰ／ＩＰ协议,在Ｉｎｔｅｒｎｅｔ／Ｉｎｔｒａｎｅｔ中具有广阔的应用前景。本文对Ｈ．３２３标准的实体及其体系结构进行了概要性的介绍,之后给出了基于Ｉｎｔｅｒｎｅｔ的多媒体会议系统和ＩＰ电话系统的组成及原理     

基于JAIN SIP/JMF的IP组播视频会议系统的设计与实现

针对集中式视频会议系统服务器负载过重的问题,讨论在NIST—SIP协议栈基础上对基于SIP及IP组播的桌面视频会议系统的设计,利用JAIN SIP技术进行SIP信令集中处理,同时利用JMF技术实现音视频媒体流分布传输,改善了太多会议参与者同时接收网络多媒体音视频流时可能带来的过长网络延时和抖动问题,减轻了服务器的负担。     

Desktop video conferencing in the organisation

While the potential advantages of video conferencing are appealing, the technology has not been implemented in more than a handful of organisations. This is likely to change in the future as video conferencing moves to the desktop. This paper examines the issues surrounding the area and, in particular, attempts to determine the impact of video conferencing on organisations. A framework is provided for understanding desktop video conferencing in the organisational context, and the relative benefits of and problems in the use of desktop video conferencing are discussed. Finally, a number of suggestions are made on how organisations may reconcile the implications of utilising desktop video conferencing technology.     

Multimedia conferencing over ISDN and IP networks using ITU-T H-series recommendations: architecture,control and coordination

This article discusses the architecture, control protocols, and coordination mechanisms used in today's multimedia conferencing standards for ISDN (Integrated Services Data Network) and IP (Internet Protocol) networks. Specifically, the ITU-T's (International Telecommunication Union – Telecommunication Standardization Sector) H.320 and H.323 multimedia conferencing standards are discussed and compared with respect to their architecture and position in the market.     

视频会议系统及应用

视频会议是指利用通信网,以电视实况方式召开的会议。通过视频会议系统,位于各地的与会者在开会时即可听到对方的声音,又可看到对方的影像,会议的场景,以及会议中展示的图片表格等。其好处是可以大大节省会议差旅费,提高办事效率,节省时间。     

Integrating Internet telephony services

Cost savings and the ease of developing and adding new services have motivated great interest in Internet telephony, which integrates services provided by the Internet with the public switched telephone network (PSTN). Internet telephony relies on several protocols, including the real-time transport protocol (RTP) for multimedia data transport and the session initiation protocol (SIP) or H.323 for establishing and controlling sessions. SIP can integrate with other Internet services, such as email, the Web, voice mail, instant messaging, conference calling, and multimedia collaboration. We have implemented a SIP-based software suite called the Columbia Internet extensible multimedia architecture (Cinema), which we installed and integrated with the existing private branch exchange (PBX) infrastructure in the computer science department at Columbia University. The Cinema environment provides interoperability with the PSTN, programmable Internet telephony services, and IP-based voice mail. It also integrates Web access and e-mail for unified messaging and supports multiparty multimedia conferencing. The setup lets us extend our PBX capacity and will eventually let us replace it while keeping our existing phone numbers. It also provides an environment in which we can easily add new services and features, including interoperation with existing multimedia tools, e-mail access from standard. telephones, network appliance control, and instant messaging support     

基于COM技术的桌面视频会议系统的实现

简要介绍了视频会议系统的软件体系结构及NetMeeting SDK的编程接口, 详细介绍了利用NetMeeting SDK提供的COM组件构建桌面视频会议系统的过程.系统采用VC 6.0和COM技术开发,大大缩短了系统的开发时间,同时也提高了应用系统的兼容性和强壮性.     

Petri net based formal analysis for multimedia conferencing services orchestration

Development of services that span over the Internet and Telecom networks is driving significant efforts towards the integrated of services offered by Telecom operators. Service-oriented communication (SOC) is a new trend in the industry to enable communication through a service-oriented architecture (SOA) and thereby package communications as services. In this paper, we firstly introduce the design and implementation for business process execution language (BPEL) based multimedia conferencing communication services orchestration, and mainly focus on the issue of guaranteeing the correctness of such applications, we presents a Petri net-based approach to analyzing the BPEL based multimedian conferencing communication services orchestration correctness and also a set of translation rules is proposed to transform BPEL processes into Petri nets. Especially, we define the correctness of multimedia conferencing services orchestration and address the verification method based on Petri nets. The algorithms and corresponding reliable issues have been proposed, such as the coverability tree for detecting flow safeness, the incidence matrix & state equation for finding reachable issues, and a transitive matrix for detecting a deadlock problem. With the Petri Net Markup Language (PNML) are introduced to transform a orchestrated services into a Petri net model, and providing an automated support for the formal analysis of their behavior. Finally, we give the conclusions.     

A Format for a Graphical Communications Protocol

This article describes the requirements for a graphical format on which a graphical on-line communications protocol can be based. It is argued that on-line graphical communications is similar to graphical session capture, and thus we propose an Interactive Graphical Communications Format using the GKSM session metafile. The discussion includes items that complement the GKSM metafile as a format for on-line interactive exchanges. One key application area of such a format is multimedia on-line conferencing. Therefore, we present a conferencing software architecture for processing the proposed format. This format specification is made available to those planning multimedia conferencing systems, as a contribution toward the development of a graphical communication protocol that will permit the interoperation of these systems.     

Very large conferences on the Internet: the Internet multimedia conferencing architecture

In this paper we provide an overview of multimedia conferencing on the Internet. The protocols mentioned are all specified elsewhere as Internet-Drafts or RFCs. Each RFC gives details of the protocol itself, how it works and what it does. This document attempts to provide the reader with an overview of how the components fit together and of some of the assumptions made, as well as some statement of direction for those components still in a nascent stage.     

A proxy architecture for collaborative media streaming

Streaming media from the Internet is a successful application for end-users. With the upcoming success of mobile devices and home networking environments, cooperation among users will become more important in the future. To achieve such cooperation, explicit middleware standards have been defined. On the other hand, Internet conferencing applications do not handle collaborative streaming sessions with individual control for each user. We propose a new concept for cooperation exemplary for collaborative media streaming using IETF multimedia session control protocols together with a proxy architecture. This concept enables both synchronization among clients and flexible control to individual users.     

The effects of multimedia communication technology on non-collocated teams: a case study

Collaborative teams are becoming increasingly important for industry, both within and across companies. There is a need for communication technology to support teams because many teams are non-collocated, or 'virtual'. Two automotive supply chain teams were observed while they were experimenting with multimedia conferencing in order to determine what support non-collocated teams need and the potential effects of introducing technologies on their group processes. The observations included meeting recordings and other sources that show the organizational factors affecting teams. Working in teams requires very close collaboration. Communication technology can help teams if it is used to foster close and relatively informal person-to-person interaction. Organizational constraints on how the technology is introduced favour high-technology, special-purpose installations, but teams can best be supported using relatively modest equipment with desktop access.     

The effects of multimedia communication technology on non-collocated teams: a case study

Collaborative teams are becoming increasingly important for industry, both within and across companies. There is a need for communication technology to support teams because many teams are non-collocated, or ‘virtual’. Two automotive supply chain teams were observed while they were experimenting with multimedia conferencing in order to determine what support non-collocated teams need and the potential effects of introducing technologies on their group processes. The observations included meeting recordings and other sources that show the organizational factors affecting teams. Working in teams requires very close collaboration. Communication technology can help teams if it is used to foster close and relatively informal person-to-person interaction. Organizational constraints on how the technology is introduced favour high-technology, specialpurpose installations, but teams can best be supported using relatively modest equipment with desktop access.