Window-level rate control for smooth picture quality and smooth buffer occupancy

In rate control, smooth picture quality and smooth buffer occupancy are both important but contrary to each other at a given bit rate. How to get a good tradeoff between them was not devoted much attention previously. To deal with this problem, a theoretical window model is proposed in this paper, in which several adjacent frames grouped as a window are considered together. The smoothness of both picture quality and buffer occupancy can be gracefully achieved by regulating the size of the window. To illustrate the usage of window model, a window-level rate control algorithm cooperated with the traditional ρ-domain rate-distortion model is further introduced. In experiments, we first show how the proposed window model achieves the tradeoff between picture quality smoothness and buffer smoothness, and then demonstrate the significant PSNR improvement, accuracy of bit control and consistency of visual quality of the proposed window-level rate control algorithm.