| People put forward the concept of the Internet of things and wisdom earth for the purpose of communication at anytime and anywhere.In the future the networks will consist of real-time multimedia networks with huge amount of things interconnected.With the rapid development of Internet and the mobile communication technology and the popularity of network access to cheap intelligent devices,the network services presents a tendency of multimedia.A variety of multimedia applications especially in real-time streaming media services spring up into all aspects of people's lives,such as VOD,video monitoring,IPTV,network broadcasting,remote education,remote medical treatment and video conference.At the same time,a huge amount of multimedia services has spawned huge amounts of information interaction.The real-time streaming media data can be characterized with mess data volume,high real time character,complex association,rapid data growth and high frequency of exchange and query.As the existence of network bandwidth fluctuation,packet loss,delay and jitter in the process of data transmission and storage,the transmission quality of real time streaming media data can not be guaranteed.Its theory and technology are facing challenges.Therefore,it is very important to study the key technologies of real time streaming media transmission system.This paper studied real time streaming media service overlay network architecture,QoS routing and control strategy,fountain code design and the realization.The main research contents and results are as follows:1.Distributed real-time streaming media service overlay network architecture is proposed.The traditional services in single real-time streaming media system,such as signaling service,forwarding service and streaming media service will be mapped into a number of service nodes in the overlay network.The overlay network consists of media signaling subsystem and media distribution subsystem.The media signaling subsystem realizes the communication between the various signaling server,media server and receiving equipments through the extensions of SIP protocol.Media distribution subsystem implements real-time streaming data distribution,which contains the technologies like fountain codec,load balancing,IP QoS and video quality control.Media signaling subsystem and media distribution subsystem communicate with each other through the Internet Communication Engine middleware technology.2.Based on the real-time streaming media transmission system architecture proposed in 1,this paper studies the QoS routing and proposes a QoS routing algorithm based on bandwidth,delay and node state.Simulation results show that the routing algorithm can effectively expand the system distributed performance and realize the load balance,increase the success probability of user request and improve the network capacity.The control scheme of QoS is presented and practical design of the delay strategy and buffer control,video parameter measurement and bandwidth estimation are given.The transmission capacity of the wireless sensor network is simulated,and the server target bitrate,output bitrate and frame rate control strategy are given.The test results show that the performance of real-time streaming media transmission has been greatly improved after the implementation of QoS control strategy.3 The application of fountain codes in real time streaming media system is studied.This paper puts forward the concept of binary erasure channel model,analyzes and points out that Internet is a typical case.It introduces the basic principle of digital fountain code,and analyzes the performance of LT codes and Raptor codes,based on which analyzes the system code packet loss recovery process,and the designs a fountain codes degree distribution for H.264 real-time video with unequal error protection called I frame distribution to improve the performance of real-time streaming media data transmission in IP network.Compared with the traditional robust degree distribution,I frame degree distribution can give the H.264 I frame high level protection according to channel erasure rate,and the receiver has a high probability to recover I-frame data,which makes the video stream a higher PSNR value.4.This paper achieves a real-time streaming media transmission system with fountain codes based on I frame degree distribution.The fountain codec is implemented on media transmitting equipment,media distribution subsystem and media receiving device to guarantee high quality transmission of I frame.Through the analysis of the delay and network communication performance,it gives the specific the encoding length reference and the implementation process.At the same time,Ice middleware is discussed and Slice interface file is designed and implemented,through which achieves the communication and load balancing between media signaling subsystem and media distribution system. |
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