Rtp-based Video Transmission Control Method

The steady advancement of technology in the field of computer networks and multimedia has become a strong impetus to the development and popularization of the networked multimedia applications. Distributed multimedia applications such as videoconference, video on demand, long-distance education, automatic monitor system etc. are slowly coming into people's life. They also bring much facilities and fun to people's work and life.But on the other hand, the best-effort service based on IP provided by Internet isn't suitable for the transmission of video information. The video information transmission always pauses or appears mosaic because of network congestion. The playback effect of video information is always affected by the fluctuation of network states. QOS is difficult to be guaranteed.Coming from a video transmission need in networked multimedia application, the research project the thesis discusses is to research an RTP-based video transmission control method, which can adapt to the changes of network states. The thesis includes the following four parts:Firstly, fast development of IP network makes transmission of digital video information real. This thesis analyzes stream media technology and video compression coding technology, then points out the key problems in networked multimedia application from many popular video transmission systems.Secondly, this thesis lucubrates the contents and characters of RTP and thinks that RTP is well suitable for the video transmission. The real-time transport protocol (RTP) drawn by IETF is a protocol worked on the top of transport protocol. RTP provides end-to-end real-time multimedia data transmission. RTCP, one of its components, can effectively control and monitor the transmission. Making good use of the control messages providedby RTCP and some control strategies, we can well control video transmission and meet some requires in QOS.Thirdly, about rate control during video transmission, this thesis analyzes several control methods and ideas, puts forward an RTP-based source video transmission control policy. This policy can make video transmission rate of sender automatically adaptive to the changes of network states and efficiently reduces network congestion.Fourthly, in order to realize RTP and transmission control policy, this thesis makes use of the platform of Microsoft DirectShow. Using the wide variety of formats supported by DirectShow and the characters based on COM, this thesis researches the architecture of DirectShow, its basic theory and construction of its basic component-filter, realizes RTP as two filters. With the help of existing capture and encode components, making use of DirectShow architecture, this thesis realizes an integrated video transmission experiment model.The main work of this thesis:The first, this thesis analyzes the contents and characters of RTP. Aiming at the characters of video transmission, it brings forward an RTP-based video transmission control method, which is mainly for rate control.The second, this thesis designs a DirectShow-based video transmission model. This model is flexible and convenient, without need to use video capture card. It can be applied to small or middle scale application.