1. INTRODUCTION
The experience of viewing videos has evolved through the advancement of video recording and viewing devices: from black-and-white videos to color videos, from television to smartphones. Nowadays, egocentric videos and 360° videos are being collected [1],[2] and studied for use in VR/AR technology [3], robotic navigation [4], skill acquisition [5], etc., and are expected to become widespread in the future. Egocentric videos are recorded from a human viewpoint by following the motion of the human body and head, and 360° videos capture a view in every direction using a omnidirectional camera and allow users to control the viewing direction. These videos are close to human vision since humans have a bounded field of view and rotate their heads to obtain information about their surroundings [6].