Image stabilisation scores a ball's-eye view of American football

The researchers from Carnegie Mellon University and the University of Electro-Communications (UEC), Tokyo have shown that a camera embedded in the side of a rubber-sheathed plastic foam football can record video while the ball is in flight.

Because an American football can spin at 600rpm, the raw video is an unwatchable blur. The researchers rectified this with a computer algorithm that converts the raw video into a stable, wide-angle view.

The BallCam system developed by Kris Kitani, a post-doctoral fellow in Carnegie Mellon’s Robotics Institute, and UEC’s Kodai Horita, Hideki Sasaki and Prof Hideki Hoike, uses a single camera with a narrow field of view to generate a dynamic, wide-angle video.

When the ball is thrown in a clean spiral, the camera records a succession of frames as the ball rotates.

When processing these frames, the algorithm uses the sky to determine which frames were made when the camera was looking up and which were made when it was looking down.

The upward frames are discarded and the remaining, overlapping frames are stitched together with software to create a large panorama.

The algorithm also makes corrections for some distortions in the image that twist pitch markings and occur because of the speed of the ball’s rotation.

Further work will be necessary to eliminate all of the distortion, Kitani said in a statement, and a faster camera sensor or other techniques will be needed to reduce blurring. Multiple cameras might also be added to the football to improve the finished video.

Horita will present a paper about BallCam on March 8 at the Augmented Human International Conference in Stuttgart, Germany.