The Design And Implementation Of Multicast Protocol Based Upon The Video Bit Rate Optimization On Broadcast Channels

The rise of services such as webcasting,video conferencing,and live videocasting makes the video multicast as a hot spot of nowadays information technology.The losses of packets are different at different users in a multicast senarios.And the receiving moments of a video at different receivers are barely the same.This leads to the problem of inconsistent delay differences between different receivers.This thesis aims to solve the problem of exsiting non-determined difference of transmission delay among multicast channels.The main work carried out are as follows.First,this thesis introduces and analyzes the characteristics of H.265 video stream data,followed by the introduction of the transmission sequence and the decoding sequence of H.265.Moreover,the basics of fountain codes is presented.Second,this thesis summarizes the dependencies of different types of data packets of video stream data in decoding,and proposes a data classification method based on reliability requirements for H.265 data packet transmission,and also designs a corresponding multicast transport mechanism.Third,under the requirement of limited time delay of video stream transmission,with the time stamp synchronization algorithm,this thesis designs a synchronous multicast protocol for synchronization and video bit rate adjustment according to the transmission delay.This protocol can reduce the video stream playback delay difference between multiple receivers.Fourth,this thesis implements the proposed protocal with C++ language.This thesis reports our experiment with a WIFI router as the central node of the wireless multicast scenario and conducts the experiments on three cases of video stream multicast synchronization protocol,i.e.,the RTP,the FCWM and ours respectively.Under the condition that the number of receivers is 5,10,15,20,25 and 30,the standard deviations of synchronization error and the average values of video decoding success rate under different conditions are recorded.The experimental results show that when there are 30 receivers,the video synchronization error of the video stream multicast synchronization protocol proposed in this thesis is reduced by 64.8% compared with that of RTP,and the video decoding success rate is increased by 50.7%.Although the video decoding success rate in this thesis is reduced by 7.5%,the video synchronization error is reduced by 61.1% compared with FCWM.