1. Introduction
Virtual reality (VR) and the 360° panoramic video format have broken the limit of the conventional rectangular cropped view of our world. We will denote the medium by 360 video for short. Due to popularity, camera devices capable of capturing 360° panoramic videos have gotten accessible over the years. Google [2] and Facebook [6] publicly released professional-grade camera rig design and stitching algorithms to stitch video stream from multiple cameras to create a single 360 video. Numerous consumer-grade camera devices are widely available off the shelf as well.