Real-time video traffic control based on time-varying channel rate and source complexity

Abstract

The main technical issue of real-time video communication is clearly the quality adaptation method, which is required to provide acceptable level of decoded video quality and the end-to-end delay guarantee. There are two time-varying factors to affect the performance of video transmission systems. The one is the time-varying effective channel rate. The other is the time-varying statistics of source traffic. It is due to the changes in the scene contents over long period of time. Thus, it is needed to consider both time-varying factors in encoding and transmission control process to guarantee the end-to-end delay and acceptable level of perceived quality. In this dissertation, we propose an explicit rate decision algorithm at the bottleneck switch and an adaptive video frame rate control method to adapt to the time-varying channel rate. Also, we propose a source traffic prediction method and a preventive channel rate decision algorithm to consider the time-varying statistics of source traffic in dynamic bandwidth allocation environment. First, a model of video transmission systems over explicit rate networks is presented and analyzed under the end-to-end delay constraint. It is shown that decoder buffer underflow is the major element to be prevented and that it should be done by controlling explicit rate feedback from the bottleneck switch. An upper bound of explicit rate is derived for single feedback connection which guarantees the end-to-end delay. It is obtained by using the state of leaky-buckets of high-priority connections and video service buffer occupancy. The same explicit rate decision mechanism can be applied to multiple feedback connections with different delay constraints by separating each connection according to the service policy. Secondly, an adaptive video frame rate control method, called AFCON, is proposed that video encoders use in conjunction with explicit rate based congestion control in the network. An encoder buffer constraint which...