The Theoretical Study Of Multi-party Video Conferencing And Video Surveillance System Of Railway

The development of video compression technology promotes the video communication technology, video conference is the typical application of video communication technology and widely considered to be an important measure for enterprises to reduce cost and improve efficiency, video conference is becoming an important network application. This paper will study relationship between the transmission of video stream and node’s upload bandwidth,download bandwidth in video conference. we establish the optimization model to obtain the maximum value of the user’s video quality, and gives the upper bound of user’s video rate.Video surveillance can be regarded as one video conference system whose video source is fixed, the viewer is fixed. It is a specific application of the video conference. Video surveillance system of railway is a video surveillance network which covers the whole railway, there are cameras in various sites, bridges and important railway stations.Monitoring personnel can play a plurality of monitoring video in the system,but the monitoring station even with high configuration can not playback these video pictures smoothly while the video channels is much more. The reason is that the Processing capacity of the the monitoring station is limited,but decoding of H.264video needs consume much CPU resources,in order To solve this problem, we designed a long-term solution and a temporary solution.the Long-term solution sets up the cloud of video transcoding to solve the Processing capacity of monitoring station.Because the construction period of the video transcoding cloud is very long, and it is urgent to solve this problem,the temporary solution can solve the problem,its basic idea is that configuration or full use of idle computers which lie in the same LAN with the monitoring station is adopted to assist in the video transcoding, these computers finish video transcoding of the multi-channel and relay the video stream to the monitoring station for playing.In this paper, the main work is as follows:First,the study of transmission of video stream in single picture and multi-picture video conference, the relations between the theoretical upper bound of user’s video quality and bandwidth resources, the establishment of optimization model of video conference, the upper bound of user’s video rate is given. Second, In order to solve the problem of The Video surveillance system of railway,the paper designs the video transcoding cloud as a long-term solution, in this scheme, the optimization model based on resource scheduling algorithm is designed.Third, a temporary solution is desinged to solve the the problem of The Video surveillance: the computers which lie in the same LAN with the monitoring station is made full use of to assist in the video transcoding,finally these computers finish these video transcoding and relay the video stream to the monitoring station。 In the laboratory’s LAN, a demo system is implemented to verify the idea.