Research And Implement Of SIP-Based Multimedia Communication

With the development of technologies in network and multimedia, and the appearance of NGN (Next Generation Network), the business of multimedia communication, especially the VoIP technology, has become a leading element in Internet applications.SIP (Session Initiation Protocol), which was developed and designed by IETF, is a session control protocol on application layer. The protocol is used for creating, modifying, and terminating multimedia sessions with two or more participants over internet. With the improvement and completeness of this protocol, SIP is widely used in various realms, such as Multimedia conference, distance education, Internet telephone calls and multimedia distribution. Because of simple structure and high flexibility, SIP is considered as a key protocol in NGN technologies and SIP related research and development has already become a hotspot in fields of telecommunication and network.In this thesis, we concentrated on the critical issues related to SIP-Based multimedia communication, designed and implemented a SIP multimedia terminal with voice and video chat function on Windows platform, and finally provided a standard multimedia communication system.The basic knowledge and related technologies of SIP were introduced, such as the syntax, architecture, call flows, network entities, authentication, NAT/FW traversal and open source SIP stacks. In addition, SIP-Based multimedia communication technologies were analyzed in detail, such as SIP extensions, SDP negotiation, Audio/Video CODEC and Message compressing. Finally, design idea and implement of the SIP multimedia terminal were elaborated, especially the key technologies related to SIP Engine and Video Engine. These key technologies include video media negotiation, video capture, encoder/decoder, data transmission and video display. The test in local area environment showed that the SIP multimedia terminal has good performance in voice and video chat.