The "Virtual" Replay
The EyeVision technology that premiered in Super Bowl XXXV is a system co-developed by CBS, Carnegie Mellon computer vision professor Takeo Kanade, Princeton Video Imaging and Core Digital Technologies.
The EyeVision system is a set number of digital video cameras arranged around the playing surface. In the case of Super Bowl XXXV, there were 30 cameras placed around the top of Raymond James Stadium in Tampa Bay, Fla. The cameras were spaced at seven-degree intervals, giving a 210-degree view around the playing field. A full 360-degree view is possible; however, it was decided to use a smaller setup in EyeVision's first broadcast.
Each camera is mounted on a robotic platform capable of precisely panning and tilting the camera in any direction. The camera's zoom focus, and the platform's pan and tilt capabilities, are computer controlled from the production truck. One camera is designated as the master camera. Using a simulated camera on top of a pan/tilt tripod, the camera operator follows the action with the master camera. By acquiring the zoom, focus, pan and tilt data from that camera, a computer can mathematically calculate what every other camera's variables should be in order to capture the same range of action on the field from different angles. A computer controls these cameras automatically. The result is a set of 30 different video sequences of the same action, covering a 210-degree range of view. These sequences are recorded on digital tape decks and time stamped in order to be collated and played back for the home viewer.
Once the video is stored in the tape decks, it can be replayed to television. The original intent of EyeVision was to produce an effect like that portrayed in the movie "The Matrix," where the camera seemed to pan 360 degrees around the main actor while he floated in midair or dodged a bullet. However, during testing, the developers working with the hardware found a better use of the system: To follow the play with one camera, pause the tape, rotate around the play (perhaps from one sideline to the other) to get a better angle of the action and then restart the replay. The bank of cameras allow the replay technicians to have an alternative to simply cutting from one replay angle to another by using EyeVision's smooth rotation capability.
This method worked extremely well this year in the Super Bowl when a runner dove over the goal line and fumbled the ball (click here to see the play). EyeVision was able to follow the play from behind and, as the player crossed into the end zone, pan around to an angle perpendicular to the goal line to show that the player still had control of the ball as it passed over the goal line, resulting in a touchdown.