The Design And Realization Of Video Conference Based On SIP

With the rapid development of multimedia and network communication technology,research and application of video conference system have become a hot topic.At present,most of video conference systems are based on H.323 protocol,which is mature but strong dependent on traditional dedicated network and hardware,it is not conducive to the popularity of video conferencing applications.SIP protocol,proposed by IETF,can achieve many functions of H.323 for its concision,flexibility,and easy extension.SIP can process signaling using software instead of hardware.The main content of this paper is designing and implementing video eonferencing system on the hardware environment of ordinary PC and media equipment.The design has two major parts including video conferencing server and video conferencing client.The system completes the multi-point call control with SIP and SDP protocol and multi-point media stream communication with JMF.Specific work of paper is as follows:First of all,SIP and SDP protocols are studied.SIP message structure and process are analyzed.At the same time,Work mechanism of RTP protocol and control protocol RTCP is discussed.In contrast to the traditional model of video conference,this paper makes some improvements.Conference model of signaling focus,media streaming distribution is designed.At the same time,based on the new model, architecture of video conferencing system is designed;interface of JAIN SIP is also realized with the open source protocol stack NIST-SIP.Call-In signaling of video conferencing system is designed.Functions of INVITE,SUBSCRIBE,and NOTIFY are achieved with the JAIN SIP technology.Media stream communication between video conferencing clients is designed with the JMF technology.Capturing,encoding,transmitting,receiving and playing back of audio/video in conference terminals are realized with JMF technique too.In order to reduce the burden of networks and systems,IP multicast technology is used in the transmission.Experimented results of system modules are tested and analyzed.This system is tested in the LAN many times,the experimented results show it can realize the video conference,and video and audio effect is clear.Through SIPFlow protocol analysis software,the analyzed results of the signaling are in accordance with Call-In signaling.Through WireShark protocol analysis software,media stream communication is in line with the form of multicast.The system achieves the desired effect.