Bullet time using multi-viewpoint robotic camera system

The main purpose of our research was to generate the bullet time of dynamically moving subjects in 3D space or multiple shots of subjects within 3D space. In addition, we wanted to create a practical and generic bullet time system that required less time for advance preparation and generated bullet time in semi-real time after subjects had been captured that enabled sports broadcasting to be replayed. We developed a multi-viewpoint robotic camera system to achieve our purpose. A cameraman controls multi-viewpoint robotic cameras to simultaneously focus on subjects in 3D space in our system, and captures multi-viewpoint videos. Bullet time is generated from these videos in semi-real time by correcting directional control errors due to operating errors by the cameraman or mechanical control errors by robotic cameras using directional control of virtual cameras based on projective transformation. The experimental results revealed our system was able to generate bullet time for a dynamically moving player in 3D space or multiple shots of players within 3D space in volleyball, gymnastics, and basketball in just about a minute. System preparation in calibrating the cameras in advance was finished in just about five minutes. Our system was utilized in the "ISU Grand Prix of Figure Skating 2013/2014, NHK Trophy" live sports program in November 2013. The bullet time of a dynamically moving skater on a large skating rink was generated in semi-real time using our system and broadcast in a replay just after the competition. Thus, we confirmed our bullet time system was more practical and generic.