In this paper, we propose a coding tree unit (CTU)-level rate control scheme from the perspective of SSIM-based rate-distortion optimization to improve the coding efficiency. First, we establish the SSIM-based rate-distortion model based on the divisive normalization scheme, which characterizes the relationship between the local visual quality and the coding bits. Then, the established model is applied to the CTU-level rate control and transformed into a global optimization problem solved by convex optimization. Finally, a new model parameter updating strategy for the CTU-level rate control is presented that is robust to scene variations. Our algorithm can achieve optimal CTU-level bit allocation given the bit-rate budget. The experimental results show that our algorithm substantially enhances the coding performance and consistently outperforms both the rate control scheme in the HEVC reference software and existing algorithms in terms of rate-perceptual distortion performance using different test configurations.
Bibliographical noteThis work was supported in part by Hong Kong ITF UICP under Grant 9440174, in part by the Natural Science Foundation of China under Grant 61801303 and Grant 61672443, in part by Hong Kong RGC General Research Fund 9042489 under Grant CityU 11206317, in part by Hong Kong RGC General Research Fund 9042322 under Grant CityU 11200116, in part by the National Natural Science Funds of China under Grant 61502277, in part by the Hong Kong RGC Early Career Scheme under Grant 9048122 (CityU 21211018), in part by the City University of Hong Kong under Grant 7200539/CS, and in part by the startup project of Shenzhen University (2018069).
- global optimization
- Human visual perception
- rate control
- rate-distortion optimization