An Optimized Rate Control Algorithm in Versatile Video Coding for 360$^\circ$ Videos

Today, 360 $^\circ$ video has become an integral part of people's lives. Despite the fact that the latest generation standard Versatile Video Coding (VVC) demonstrates a significant gain in encoding capacity over High Efficiency Video Coding (HEVC), it still has room for 360 $^\circ$ video encoding improvements. To further enhance the applicability of 360 $^\circ$ video coding, an optimized rate control (RC) algorithm in VVC for 360 $^\circ$ video is proposed in this paper. We present an efficient extraction algorithm for obtaining the video's saliency feature. Furthermore, for the characteristics of 360 $^\circ$ video, a partitioning algorithm is also proposed to divide a frame into demand and non-demand regions. Additionally, to achieve precise and rational RC, a Coding Tree Unit (CTU)-level bit allocation strategy is proposed based on the saliency feature for the above-mentioned regions. The experimental results show that the proposed RC algorithm can achieve 11.77 $\%$ bitrate savings and more accurate allocation compared with the default algorithm of VVC. Also, performance enhancement has been observed in comparison to the most advanced algorithm.