| This paper studies the key technologies of multimedia communication terminal equipment system, with emphasis on system analysis and implementation, video and voice codecs are not studied in detail. Low bit rate multimedia communication terminal systems are studied in the first part of this paper. In the first chapter, a multifunctional communication terminal for PSTN, which can communicate with still image, data and voice, is implemented, the terminal has been transferred to commercial production. The second chapter studies H.324 low bit rate mulimedia communication terminal. The terminal has adopted the latest modem , video codec and voice codec technology. Its way of multiplex is specially suitable for simultaneously transmitting of both real time and non real time traffic, as the multiplex layer assigns different byte positions in a multiplex PDU to data of different media dynamically The market prospect of H.324 terminal depends on its cost. The second part of this paper studies ISDN multimedia communication terminal. An ISDN multimedia communication terminal offering voice and data service is implemented in the third chapter The terminal is composed of a PC computer and an ISDN communication card with CPU on board which is used to access ISDN. User interface and shared board are realized under WINDoWS environment on the PC computer, shared board offers a lull duplex, gr3phical data communication environment to the user. The fourth chapter studies and achieves the function of ISDN terminal to access INTERNET The fifth chapter studies multipoint AV communication based on ISDN, the implementation method of an MCU for multipoint AV communication based on ISDN, whose major functions include voice mixing and video switching, is proposed after a full study on ITU-T H.320 series recommendations. The sixth chapter studies data protocols for multipoint multimedia communication. The implementation of a multipoint multimedia communication system is ready to begin on the basis of the research work of chapter 5 and chapter C. The third part studies ATM multimedia communication terminal. ATM terminal system is analyzed in the 7th chapter, and in the 8th chapter, a design of the hard ware structure of ATM terminal is given and the control plane software is implemented, which has successfully interconnected with its peer one on the switch side. Multimedia communication includes many theoretical problems. The 4th part studies media synchronization and Usage Parameter Control. Available media synchronization models are not fully suitable for distributed environment, in which the length of media display interval and the inter-relationship between intervals are not certain. The 9th chapter studies basic concepts of multimedia, makes clear the problem of media synchronization, classifies available media synchronization models, and proposes a new media synchronization model which is simple, powerful and suitable for distributed environment. ATM features that various user traffic are statistically multiplexed when accessing network, the network have to monitor and control user information flow through UPC operation. ATM network will take proper measure, such as discarding cell, when user information flow violates negotiated usage parameter. UPC should be fast in reaction and sensitive in selectivity. Fast in reaction means the network should take control measure as soon as the user traffic occupies too much network resource in case that the QOS of the whole netw... |
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