Design And Implementation Of The Network VideoTransmission System Based On TURN Protocol

With the development of computer technology and multimedia technology, thevideo coding technology and real-time transmission technology gradually becomebetter and better, more ways to communication conveniently are desired. Real-timevideo transmission system begin to play a greater role in many fields such as videoconference, distance education, real-time monitoring system and so on. Real-timevideo transmission system which is stable and easy to use is largely demanded.This isthe reason why this paper is researched.The network technology develops rapidly.It is an opportunity for the videotransmission system.However, it also makes the research experience new problems.Internet gains its popularity, and computer has become a necessary thing for familiesand individuals.Billions of computers need to access Internet.Gradually IPv4addressbecomes rare. But the IPv6technology is still under investigation.What is worse, thequantity of work to transform the entire network is very huge. So we can only look forsome other ways to relieve the IPv4address problems. So there comes networkaddress translation technology which is shortly called NAT.Using NAT, lots ofprivate network addresses from one LAN are mapped to a same public IP address, somultiple devices can be connected to Internet with only one public networkaddress.NAT greatly reduces the need for public addresses. NAT device limits theend-to-end communication, so I have to solve the problem of NAT traversal while thevideo transmission system is designed and implemented.In order to complete the video transmission system, this paper researches themain technologies needed. Video4linux2is used for video capture, then I encode thevideo data with the H.264video coding standard. I choose RTP protocol to transfer the video data, and RTCP protocol to control RTP, and RTSP protocol to control thestreaming.I also designed TURN server for symmetric NAT to achieve NAT traversal.The video transmission system is divided into three parts: a video sender,aTURN server and a video player. The video sender achieves the functions of videocapture, video encode and video data transmit. Video capture module can collectvideo information from a camera, and encode the video data with the H.264codingstandard.This makes the transmission of video data easier. The video transmissionmodule uses an open source streaming media server which is called Live555, usingRTSP protocol to control the transmission of video data stream. TURN server is atransfer station between the video sender and video player. Every message or datafrom video sender and video player should be sent to the TURN server, then they willbe forwarded to their destination. The video player is a Android mobile phone APPwhich is based on VLC open source library. The video player achieve the function oflogining, sending request for video, decoding and playing after receiving the videodata. In this paper I have discussed the needs analysis and functional design of thethree parts,and then I wrote the specific design of the video capture module, videoencoding module, video transmission module and the implementation of TURNserver.After testing, the system has basically achieved the design goal. The client,which is in the symmetric NAT can receive and play the video captured bycamera.The result proved that video sender, TURN server and the video player allcan run correctly.