Viewport-adaptive 360-Degree Video Coding Using Non-uniform Tiles for Virtual Reality Communication

360 degrees video can provide users with immersive experience by showing the omnidirectional perspective, which is getting more attractive to consumers. However, 360 degrees video tends to have higher resolution, resulting in increased bandwidth requirements for transmission. The characteristic of head-mounted displays (HMD) provides a new approach to reducing the cost of streaming 360 degrees video bandwidth, which can encode 360 degrees video by considering user's orientation. In this paper, we propose a novel 360 degrees video coding method based on the characteristics of Equi-rectangular Projection (ERP) and combined with user-oriented behavior. Specifically, a non-uniform tile method according is designed to the principle of ERP, which also meets the behavioral of users viewing 360 degrees video. Additionally, appropriate coding parameters are set according to the positions of different tiles to reduce the redundancy introduced by oversampling to improve the coding efficiency. Experimental results show the proposed method can reduce the bandwidth requirement of streaming 360 degrees video while ensuring the consistent visual quality, significantly.