Design And Realization Of VoIP Terminal Based On SIP

With the network equipment continue to improve, audio and video transmiting on the Internet are feasible and then the VoIP come into being. The inter-connetion capability and the media synchronization are the main obstacles in way of the developing for VoIP. This paper mainly deals with SIP signling and media synchronization.Paper introduces the pricinple of VoIP and its key technologies. According to the requirement of desktop application, paper puts forward a solution for VoIP terminal. The solution takes embedded processor PXA270 as its main CPU, and Linux as its operating system. Paper maily discusses the module of SIP signling and the module of media synchroniation. In the design of SIP signaling module.after studying and researching of SIP protocol and by relevant comparison with H.323,paper brings about a solution based on transition state machine,it define a set of api for user applicaition and then simlpe the complicative control for signaling.In the design of media synchronization module.Paper takes all the facts list as followed: the perceive ability, the requirement of Real time transmition,the capability of terminal and the capability of internet. This solution is a integrated solutions based on RTP and SIP.The programme mainly to audio streaming media, use of time-stamp in RTP, audio use of synchronization strategy based on playback time, in the mean while video refer to audio for the time, regulate play rate dynamicly. At the same time, Receiver monitors the congestion condicion and adjust video stream sent of the source dynamicly by the mechanism of SIP re-INVITE .Finally, this paper design testing solution for the VoIP terminal. The test results show that this module of SIP and the module of media synchronization work effectively.