Research And Realization Of Multimedia Softphone Based On SIP Protocol

With the increasing developments in the multimedia computer technology and the communication technology, the information that the network transports gains more and more rich. Currently the Internet is developing towards multimedia integrate services. Multimedia communication is becoming a key technology in the communication field. Many real time multimedia applications are fast developed, such as VOD, IP telephone and remote teaching and so on. As lots of media appears, a flexible dialog control facility is imperative. The SIP meets such demand. It is a control protocol for creating, modifying and terminating sessions.In the thesis, the objective is to propose an SIP-based system modal of real time multimedia that is easy to be integrated with other application software.Firstly, the paper outline the latest development of VOIP, analyze the architecture, functions and call process of SIP in details, then show the supervisory of SIP by comparing it with another similar protocol H.323. Secondly, we introduce the working principle of real time multimedia communication, put the emphasis on the main technology of implementing SIP stack and put forward a realization frame. We also described briefly the contents, characteristics and principle of RTP/RTCP protocols that are used to transmit real time multimedia data. What is more, a system modal of it is brought forward and the realization of the client with VC++6.0 is illustrated in details by system analyzing. It is proved that the system used to transmit multimedia data over SIP protocol is very easy and effective,and stand out an improved LZW Algorithm which realized the compression of SIP messages to decrease the transmission delay and shorten the session setup-time.Finally the future works which are integrated multimedia services by SIP is addressed. Then give the disadvantage of the system and present some ideas to improve it and make it prefect.