Fast CU Partition Algorithm For 360-Degree Videos on VVC

360-degree videos (abbreviated as 360 videos) have gained widespread popularity due to their immersive experience. The massive amount of video data resulting from ultra-high resolution of 360 videos makes the coding process extremely complex and seriously limits their widespread applications. In this paper, we propose a new fast-Coding Unit (CU) partition algorithm for 360 videos based on Versatile Video Coding (VVC). The major novelty is that we establish databases and develop models based on stretching and split mode (SM) distribution for 360 videos on VVC. Specifically, first, we establish stretching-based CU partition databases for 360 videos. Second, we propose a new stretching-based multi-scale convolution kernel network structure and a corresponding synthetical loss function, which further considers both Rate-Distortion cost and imbalance issue. We then develop a unique multi-threshold selection scheme to select candidate SMs. Experimental results demonstrate that the proposed algorithm improves encoding speed by 69.63%, with only a 2.28% increase in Bjøntegaard Delta Bit Rate (BDBR), outperforming the state-of-the-art methods.