Design And Implementation Of Low-rate Network Shangsheng Figure Conferencing Systems

With the advent of high-speed networking and high-performance computer technologies, distributed multimedia applications are growing rapidly in a variety of fields. As an effective and economic way of collaboration, multimedia conferencing applications are attracting more and more attention from education, research and business.The purpose of this research project has been to develop a multiparty desktop conferencing system that can utilize the current devices and low-speed computer networks in China.Enabling technologies for desktop conferencing are discussed first, including some useful concepts, the compression of audio and video data and networking technologies and protocols, such as the ATM, TCP/IP, XTP and RSVP. Then, the author presents the architecture of multimedia conferencing systems, including the physical and logical architectures. Some popular multimedia conferencing systems are introduced.In this thesis, a multiparty conferencing system named Voice and Graphics Conferencing System is described in detail. The client/server based architecture of the system is flexible and general for a lecture mode conference in which a chairman takes charge the meeting and the users can join the conference at any time without disturbing other participants. In our VGCS system, TCP/IP and RTP protocols are used to implement the communication feature of the system. A special component is the Conference Information Database Manager Module that can use to backup manage the information of lectures and conferences. Since audio is more important and people are more sensible to audio jitters, the goal of our system is to maximize the quality of the audio delivered to the destinations. To achieve this goal, we describe a set of control mechanisms including the receiver's audio buffers and silence detection. All the important implementation of the system are given. A friendly user interface is provided to facilitate user's interaction with the system. We analysis the system performance and the factors which influence it.Recommendations for future work are also made.