Viewers of televised football games can now see footage from video cameras mounted on the players’ helmets and the coaches’ heads ... what else could one ask? Of course, let’s see what things look like from the ball’s point of view! Actually, that’s no longer as far-fetched as it once was. Researchers from Carnegie Mellon University and Japan’s University of Electro-Communications (UEC) recently unveiled their BallCam system, which can provide relatively smooth video from a spinning, airborne football.
Developed mainly by Carnegie Mellon post-doctoral fellow Kris Kitani and visiting UEC grad student Kodai Horita, the BallCam prototype itself is simply a rubber-covered foam football, with a GoPro HERO 2 camcorder wedged into a hole cut in one of its sides.
When that ball is thrown in a spiral, spinning at up to 600 rpm, the video captured by the camera is not surprisingly quite chaotic-looking. By processing that video after the fact using a custom algorithm, however, a steady, consistent shot emerges.
In order to do this, the algorithm looks for the sky in every frame of video – this lets it know whether the camera was facing up or down in each frame. In cases where the camera was just shooting the sky, the frames are discarded. The remaining frames – which all overlap the frames to either side of them to a certain extent, content-wise – are then stitched together to form a panorama. When those panoramic images are run together in quick succession, viewers see a wide-angle view from the side of the spinning ball.
A somewhat similar system is used by Lockheed Martin’s spinning Samarai Flyer micro air vehicle. It’s able to consistently capture a frame of video at the same point in every one of its rotations – when those frames are played back-to-back, the resulting footage looks like video shot from an ordinary, non-spinning aircraft.
The BallCam algorithm is also able to correct some visual distortions caused by the spinning movement. Kitani admits that there’s still work to be done in that area, however, plus he would also like to use a faster camera sensor to reduce blurring, and perhaps even equip the ball with more than one camera.
Additionally, he realizes that such a football would probably never meet approval for actual league use, but thinks that it may have applications for training, or for use in film and video production.
Footage shot using the BallCam can be seen in the video below.
Source: Carnegie Mellon University
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