VARIABLE BIT-RATE VIDEO TRANSMISSION UNDER USAGE PARAMETER CONTROL

This paper proposes a method of video bit-rate control for the case wh ere the average transmission bit-rate is constrained, considering the usage parameter control in an ATM network. By a simulation, the video quality and the network congestion probability of the variable bit-rat e (VER) transmission system, with the constrained average bit-rate, ar e compared to those of the conventional constant bit-rate (CBR) transm ission system or the VER transmission system without the rate control. The relations among the length of the sliding window (SW) to monitor the average bit-rate, the video quality, and the network congestion pr obability are analyzed. With respect to the video quality, it is shown that the VER transmission with the average bit-rate control exhibits a stable image quality when SW is long and exhibits a better image qua lity than the CBR transmission for the cases of scene change and the p anning scene. When the scene changes, the image quality changes and th e VER transmission with the bit-rate control does not exhibit a stable image quality compared to the VER transmission without the bit-rate c ontrol. With respect to the network congestion probability, it is show n that the probability is decreased greatly by constraining the averag e bit-rate and the probability becomes less when SW is made shorter. F inally, it is shown that SW should desirably be long to stabilize the video quality but the permissible length of SW depends on how many vid eo signals can be multiplexed in the network.