Perception-Based CTU Level Bit Allocation for Intra High Efficiency Video Coding

The conventional rate control algorithm does not fully consider the characteristics of the Human Visual System (HVS). To address this problem, in this paper, a perception based Coding Tree Unit (CTU) level bit allocation algorithm for intra High Efficiency Video Coding (HEVC) is proposed, which aims to minimize the perceptual distortion of each CTU under a given bit rate constraint. Firstly, to better represent perceptual distortion, Perceptually Weighted Mean Squared Error (PWMSE) is adopted instead of Mean Squared Error (MSE). Then, the relationship between Rate ( $R)$ and Perceptually Weighted Distortion ( $D_{p})$ is formulated by the proposed R- $\textit{D}_{p}$ model. Finally, the perceptual weighting factor derived from the R- $\textit{D}_{p}$ model is used to guide CTU level bit allocation. Experimental results show that the proposed algorithm achieves 6.27% bit rate reduction and 0.38 dB Bjontegaard Delta Perceptually Weighted Peak Signal to Noise Ratio (BD-PWPSNR) gain on average. Under other seven quality evaluation metrics, the proposed algorithm achieves from 1.57% to 8.95% average bit rate reduction while maintaining the perceptual quality, which significantly outperforms the benchmark schemes. Moreover, the proposed perception-based CTU level bit allocation algorithm also maintains a high rate control accuracy, which reaches 99.997%.