Research On The Core Mechanism And Implementation Technique Of ITU-T T.120-Based Multimedia Cooperative Platform

With the development of society and economy, there is an increasing demand for cooperative work. As an efficient and low-cost way for cooperation, remote cooperation technology has became a hotspot of CSCW(Computer Supported Cooperative Work ) research. Branchs of this technology include cooperative platform, multimedia communication and so on.Current technology of cooperative platform performanced bad when referring to its expansibility, universality and its ability to share data. As for China, there is a long way to go to catch up with the development of this technology. Most Chinese enterprises produce their cooperative software simply by making integration of current products or doing re-development. Therefore, it is quite valuable to do research on the core mechanism of cooperative platfonn and develop our own platfonn software which can be used as core component of CSCW applications.All considered, this paper offered and implemented a cooperative platform model IMCF which was based on T.120 protocol of ITU (International Telecommunication Union). This platform uses a T.120 protocol stack, which was developed independently, as its communication engine, enabling it to provide a universal, multipoint communication. Additionally, this platfonn uses Chinese newest audio and video coding standard, which also named AVS, to support audio and video communication. Based on IMCF, this paper made a detailed research on network transmission arithmetic of AVS video codes.Main contribution the author made in this paper can be concluded as follows:1. According to its own characteristics of cooperative platfonn, this paper provided a multimedia cooperative platform model IMCF, and specified its system structure.2. This paper made a detailed analysis of T.120 protocol, especially the lower protocols of T.120 protocol stack, including T.123, T.122/T.125 and T.124. Based on current research of ICA (Institute of Computer Applications), on which the author works, this paper developed a T.120 protocol stack software named T.120 Engine to offer multipoint communication and system control. Supplementations which the author made included token mechanism and channel mechanism.3. This paper also designed and implemented audio and video communication system of the platform and offered a solution for audio and video communication under NAT. This solution is effective in all NAT devices but symmetric ones.4. Based on IMCF, this paper did research on network transmission arithmetic of AVS video codes, and provided a packing arithmetic for AVS video codes. This arithmetic was based on MTU (Maximum Transfer Unit) and semantic partition, and could enhance error-resistibility of AVS video codes.5. A virtual learning system, SynLearning, was made to testify validity of our platform. SynLearning has been used in some education department of Shanghai and the feedback is good.