FUZZY-BASED RATE CONTROL FOR REAL-TIME MPEG VIDEO

In this paper, we propose a fuzzy logic-based control scheme for real- time motion picture expert group (MPEG) video to avoid long delay or e xcessive loss at the user-network interface (UNI) in an asynchronous t ransfer mode (ATM) network. The system consists of a shaper whose role is to smooth the MPEG output traffic to reduce the burstiness of the video stream. The input and output rates of the shaper buffer are cont rolled by two fuzzy logic-based controllers. To avoid a long: delay at the shaper, the first controller aims to tune the output rate of the shaper in the video frame time scale based on the number of available transmission credits at the UNI and the occupancy of the shaper's buff er. Based on the average occupancy of the shaper's buffer and its vari ance, the second controller tunes the input rate to the shaper over a much larger time scale by applying a closed-loop MPEG encoding scheme. With this approach, the traffic enters the network at an almost const ant bit rate (CBR) (with a very small variation) allowing simple netwo rk management functions such as admission control and bandwidth alloca tion, while guaranteeing a relatively constant video quality since the encoding rate is changed only in critical periods when the shaper buf fer ''threatens'' to overflow. The performance of the proposed scheme is evaluated through numerical tests on real video sequences.