Research On The Synchronization Question In The Multimedia Communication

The existing Internet is a kind of network that provides the best-effort service, and it adopts the TCP/IP protocols. And such sequential data streams as the video and audio need to be disposed in the multimedia applications real-timely. The existing network not only can't provide the guarantee to the QoS during the communication, but also a series of questions such as network delay, delay jitter, congestion, error, loss and so on will be caused by network medium, ability to endure the load, choice of the router and etc. In the end, some phenomena including image jitter, mosaic, loss of synchronization and etc. will affect the play quality of the receiver end. So it is necessary to take effective measures to dispel the delay jitter or lessen the jitter value, and make the synchronization error of each media after transmitting in the acceptable range by people. This thesis aimed to study the synchronization mechanism that will provide the high quality of service, and alleviate the network load. The main work as follows:Firstly, in order to study the synchronization control tactic in the multimedia communication, the network demands of multimedia communication has been analyzed in this thesis, and the performance parameters has been provided. Then such key technologies as the compression technology, transmission technology, and QoS technology, etc. have been studied systematically. In the end, the merits and demerits of solutions were compared, and such key control mechanisms as the flow controlling, buffer controlling were summarized in the multimedia communication.Secondly, the buffer controlling mechanism is one of the focal points in this thesis. In order to avoid such state as the serious data loss and overweight network load caused by the overflow or underflow of the buffer, the buffer is adjusted dynamically according to the occupation rate of the buffer in this thesis. The loss rate of the receiver end has been regarded as the secondary decision terms because the reason causing the deviant occupation rate isn't single. The state of occupation rate and loss rate determined the corresponding adjustment measure together.Thirdly, the flow control is also one of the focal points in this thesis. The flowcontrol mechanisms play a very important role for adjusting the network state and guaranteeing the broadcasting quality. The sending rate has been adjusted dynamically based on the AIMD arithmetic according to the loss situation of the receiver end in the thesis. The characteristic of design is to adjust the sending rate according to the feedback control function. When the loss rate is relatively greater, the multiplicative decrease arithmetic is adopted, and the control function is designed according to the degree of the current loss rate deviating from the normal range. When the loss rate is relatively less, the additive increase arithmetic is adopted, and the control function is designed according to the thought of using the smoothed number of lost data packets of unit time to compensate the sending rate.Fourthly, the emulation experiment was made about the synchronization control model. In the end, it got the effective result.Fifthly, the end-to-end video transmission subsystem was designed and realized with the synchronization control.