Stochastic rate-control of interframe video coders for VBR channels

We propose a new algorithm for the real-time control of an inter-frame video coder operating with a variable rate channel such as wireless channels or the Internet. Using techniques of stochastic dynamic programming we obtain off-line optimal policies from stochastic models of the channel and coder which minimize the average expected distortion. The on-line complexity of our approach is only that required to identify the state of the system (source and channel). The state of the channel is obtained based on the ARQ error-control mechanism, and the source state is computed as complexity measurements on each incoming frame. Simulation results based on this new approach are provided and compared to other proposed rate-control strategies. They show how our model-based optimal policies outperform the other considered approaches keeping a negligible on-line computational cost. This result is very interesting when considering an alternative to traditional costly solutions based on deterministic dynamic programming.