Key Technologies Of Wireless Network Live Streaming System

With the rapid development of Internet and multimedia technologies,streaming media broadcast technology has been applied widely.In recent years,the rapid development of wireless network and the increasing wireless bandwidth make it possible that streaming media technology is used in the wireless network.Currently,the streaming media based on wireless network is a research focus,and it is also a difficulty.But wireless network video broadcast today is plagued by variability in throughput and delay due to network congestion and the heterogeneous infrastructure,which impact the playback quality badly.In addition,network bandwidth becomes more and more limited upon the rapid increasing of Internet user.It is much more important to study the quality of wireless video transmission.This paper researchs technologies about streaming media broadcast,the main work we have done can be summarized as follows:Firstly,this paper research transmission protocols and coding standards.MPEG-4 can conquer bandwidth bottleneck of the network,save the resource of conununication line and realize the low bit rate and high quality of image transportation.RTP/RTCP is a video transportation protocol based on TCP/IP.It is more effective than TCP and more realiable than UDP.As a result,it is worthwhile to choose MPEG-4 as the compression standard and RTP/RTCP as the real time transportation protocol for system.Secondly,about wireless rate control during video transmission,this thesis analyzes several congestion control methods and ideas,based on AIMD congestion control methods,this thesis puts forward a video transmission control policy,simulate it in NS2 and make use of the policy in the streaming media system.This policy can make video transmission rate of sender automatically adaptive to the changes of network states and efficiently reduces network congestion.Thirdly,we study the buffering overflow problem caused by high coding rate,and give out a server buffering method.Because the wireless client is easy to flitter and lose data packet,we propose a client buffering management strategy and use client buffering management module to deal with data packet out of order and flitter.Fourthly,based on the study of wireless streaming media key technologies,this paper proposes a solution for streaming media system,and designs the system,including capture module,encode module,network transport module,decode module and playback module.The function of video capture,video encoding,real-time transmission,video decoding,playback and storage are finished.Based on the development,video transmission rate of sender and packet loss on the QOS are analyzed in the paper.Through experiment,the results indicate that the system archives good perceptual picture quality under varying network conditions and efficiently utilizes network resources.