Featuring with more uniform sampling density in the sphere domain and less non-uniform geometric deformations in the planar domain, variants of cubemap projection (CMP) format enable the higher compression ratio in on-going 360-degree video coding standardization. Different from single-view videos, 360-degree CMP videos feature with content discontinuity combined with the abrupt change of motion vectors between some adjacent faces. However, there is few bit allocation scheme designed for rate control of video coding of CMP format. Thus, this paper proposes a region-level bit allocation scheme for rate control of interframe coding of CMP format. The proposed scheme consists of two parts. The first part is machine learning based high HEVC coding cost region detection for individual faces, where the feature descriptor of a CTU consists of the face based texture complexity, motion magnitude, motion density, and temporal coherence of motion vector. The second part is fitting function based region-level bit allocation. Different from previous work, bits are assigned to the high coding cost region and non-high coding cost region in individual faces of CMP format. Experimental results indicate that the proposed scheme achieves higher bitrate accuracy and larger BD-WS-PSNR compared with the original rate control scheme of the reference software of HEVC, HM16.16 with the 360Lib.

立方体贴图投影 (CMP) 格式的变体具有球域中更均匀的采样密度和平面域中更少的非均匀几何变形，可在正在进行的 360 度视频编码标准化中实现更高的压缩比。与单视图视频不同，360 度 CMP 视频具有内容不连续性以及某些相邻人脸之间运动矢量的突然变化的特征。然而，针对CMP格式视频编码的码率控制而设计的比特分配方案很少。因此，本文提出了一种区域级比特分配方案，用于CMP格式的帧间编码的速率控制。提议的方案由两部分组成。第一部分是基于机器学习的个体人脸高 HEVC 编码成本区域检测，其中，CTU 的特征描述符由基于面部的纹理复杂度、运动幅度、运动密度和运动矢量的时间相干性组成。第二部分是基于拟合函数的区域级比特分配。与之前的工作不同，在CMP格式的各个面中，比特被分配到高编码成本区域和非高编码成本区域。实验结果表明，与HEVC参考软件HM16.16和360Lib的原始码率控制方案相比，所提出的方案实现了更高的码率精度和更大的BD-WS-PSNR。位被分配到 CMP 格式的各个面中的高编码成本区域和非高编码成本区域。实验结果表明，与HEVC参考软件HM16.16和360Lib的原始码率控制方案相比，所提出的方案实现了更高的码率精度和更大的BD-WS-PSNR。位被分配到 CMP 格式的各个面中的高编码成本区域和非高编码成本区域。实验结果表明，与HEVC参考软件HM16.16和360Lib的原始码率控制方案相比，所提出的方案实现了更高的码率精度和更大的BD-WS-PSNR。