Region-of-interest based rate control scheme with flexible quality on demand

Conventional rate control schemes focus on making output bit rate approach a target value and are deficient in ensuring a higher quality of ROI (Region of Interest) than others in a frame. In this paper, we propose a new scheme for H.264/AVC, aiming to allocate more bit resource for the encoding of ROI and still maintain the accuracy of the output bit rate. ROI-based rate control algorithms can find their specific advantages in video telephony and video surveillance applications. Our proposed scheme is based on the one implemented in H.264/AVC JM software, but enhanced with several features: ROI determination with saliency map, tunable quality factor for ROI, two-channel (ROI & non-ROI) rate control, and QP adjustment with constraints from temporal and spatial domains, as well as from ROI/non-ROI adjacency boundaries. Experiment results show both advantages in objective PSNR and subjective evaluations for ROI, while making the output bit rate accurate as before.