A Foreground-Background-Based CTU λ Decision Algorithm for HEVC Rate Control of Surveillance Videos

Although HEVC rate control can achieve high coding efficiency, it still does not fully utilize the special characteristics of surveillance videos, which typically have a moving foreground and relatively static background. For surveillance videos, it is usually necessary to provide a better coding quality of the moving foreground. In this paper, a foreground-background CTU lambda separate decision scheme is proposed. First, low-complexity pixel-based segmentation is presented to obtain the foreground and the background. Second, the rate distortion (RD) characteristics of the foreground and the background are explored. With the rate distortion optimization (RDO) process, the average CTU lambda value of the foreground or the background should be equal to the frame lambda. Then, a separate optimal CTU lambda decision is proposed with a separate lambda clipping method. Finally, a separate updating process is used to obtain reasonable parameters for the foreground and the background. The experimental results show that the quality of the foreground is improved by 0.30 dB in the random access configuration and 0.45 dB in the low delay configuration without degradation of either the rate control accuracy or whole frame quality.