Adaptive QP with Tile Partition and Padding to Remove Boundary Artifacts for 360 Video Coding

To adapt to existing high-efficiency video coding standards or technologies, 360 video is represented by different projection formats with one or multiple planes. However, continuous spherical content will have discontinuous boundaries on representation planes, which results in obvious artifacts on viewing viewports rendered from coded projection formats. To solve this subjective issue, a boundary based adaptive QP method together with tile partition and padding is proposed in this paper. Tile partition and padding can effectively reduce obvious seam artifacts. Boundary areas are coded with better quality by using lower QP to further reduce visible artifacts. Experiments are conducted based on hybrid equi-angular cubemap projection (HEC). Experimental results show that the proposed method can significantly improve subjective quality by removing boundary artifacts for 360 video coding.