Quality-adaptive media streaming
In this study, an adaptive method for maximizing network bandwidth utilization for real-time media streaming applications is presented. The proposed method implements a rate control approach over the transport protocol RTP. RTP is coupled with an existing multimedia codec, H.264. A controller that keeps the RTP packet loss fraction at a predefined reference point is implemented. During the course of the stream transmission, the information about the network state is generated by the RTP/RTCP and sent to the server by the clients. Packet loss fraction parameter is fed into the controller. Controlling the multimedia codec bitrate directly affects the packet transmission rate, therefore RTP packet transmission rate is also controlled. Two control approaches are proposed. Firstly, a PID controller is introduced. This PID controller is designed without any self adaptation and manually tuned to maximize all of the available bandwidth. Secondly, a model reference adaptive controller (MRAC) is proposed. This MRAC controller constantly adjusts its parameters according to a reference model. The output of the TCP Friendly Rate Control Algorithm (TFRC) is used as the model to keep the MRAC controller friendly towards other flows flows at a level that the application requires. Simulations are provided to demonstrate the operation of the proposed methods. In the simulations, a content streaming scenario is run against background traffic for the available bandwidth in a bottleneck network configuration.