Transmission And Playback In Streaming Media Based On Advanced Control Theory

The rapid development of the computer and network technology and video compression coding, especially the popularization of broadband and Internet, stimulates the development of streaming media greatly. Because of the inherent "best effort" characteristic of Internet, it cannot guarantee the Quality of Service of the streaming media.So streaming media system should provide adaptive control mechanism of transmission and playback according to the network bandwidth fluctuation. The transmission control of streaming media is full of challenge, it involves network congestion control,meidia synchronization and Quality of Service in realtime. Although there are some achievements of control theory on the research of transmission and playback, it is very difficult to achieve satisfactory result due to the complexity of streaming media model such as difficult modeling, time varying parameters, and integral delay etc. So we use advanced control theory as research tool in the transmission and playback control, including system modeling, stability analysis, optimization under the constraint of bandwidth and transmission delay.The main works and contributions of this dissertation are summarized as follows:A practical system identification approach is adopted to identify the rate control model based on buffer control. UDP is commonly used as the transmission protocol for real time property. The accurate model can’t be analysed by the least squares estimator for the experiment data relevance and dynamic and steady error is very big. We testify, supplement and improve the rate control model based on buffer control by data analysis and theoretic proof.The stable and smooth transmission mechanism is studied. QoS guarantees are mapped into the feedback control framework as index and constraints,in which two main factors bandwidth constraint and minimum network bandwidth fluctuation are added as constraint into the controller design.Combined with the model identified he stable and smooth transmission mechanism is solved by DMC in advanced control,which is a classical algorithm in the predictive control. QoS guarantees are achieved.A framework of realtime streaming media transmission based on TFRC is constructed. We get the playback rate model by doing theory analysis on playback in the framework.. The playback rate is controlled by classic PI controller, which is applied to achieve continuous media playback by controlling the buffer level of the sink under playback rate constraints. The effect of transmission delay on the streaming media system is studied. The inherent problem of existing control method is pointed out. Data transmission in the source and playback in the sink are applied to control the buffer length of the sink simultaneously, on which dual mode control is applied by changing the structure of controller in order to improve the performance of transmission delay. An internal mode feedback control of sending rate in the source is adopted to overcome the adverse effect caused by propagation delay, and a simple PI controller of playback rate in the sink is also adopted, which can deal with transmission delay simultaneously.A transmission algorithm of adaptive buffer setpoint trace in real-time stream media based on MVC (Minimum Variance Control) is proposed in order to get synchronization performance ganrantee under the realtime constraint in the streaming media system and to deal with the conflict between synchronization and playback delay based on buffer maximization. The buffer level is dynamically adjusted and MVC is used to track the buffer setpoint and reduce effect of the overshoot on realtime constraint. Simulation experiments that have been conducted prove that the proposed algorithm is effective.