Preventing Movie Piracy

Researchers are developing tools to thwart the copying of films in theaters.

Last month, we ran a story about an experimental device for locating and blocking cameras ("Lights, Camera -- Jamming"). Here we look at another set of technologies aimed at dissuading would-be bootleggers.

Thomson’s prototype anti-piracy system inserts extra frames into a movie that contain text or obscure the scene. The frames flicker at a frequency imperceptible to the human eye, but picked up by camcorders, thereby ruining a bootlegged movie. (Credit: Thomson.)

The movie industry has a problem. According to the Motion Picture Association of America (MPAA), Hollywood loses billions of dollars a year on illegally sold copies of movies. The losses are impossible to calculate accurately, of course, since it's unclear how many of the people who download copies over the Internet or pay a few dollars for a pirated DVD would have paid $9 to $20 for a theatre ticket or legal DVD. Nonetheless, studios and theatre owners are eager to find ways of safeguarding their intellectual property.

Paris-based Thomson, which provides technology to the entertainment and media industry, is exploring methods for thwarting at least one type of bootlegger: the covert camcorder user. The company's technique involves inserting "artifacts" -- extra frames, flashes of light, or pixelated grid patterns -- into a movie during its digital-processing phase, before it's shipped to theatres. The goal is to mar a camcorder recording without degrading the images moviegoers see, says Jian Zhao, chief technology officer of subsidiary Thomson Content Security in Burbank, CA.

The artifacts exploit the differences in the way a human brain and a camcorder receive images. In the technique that's furthest along, extra frames -- with the words "illegal copy," for instance -- are inserted into the film. These warning words flicker by at a frequency too fast for the human brain to process -- yet they appear in a camcorder recording.

This difference is possible because movies are projected as a series of still shots. Film projectors flash 48 images per second (24 frames are collected each second, but each frame is flashed twice) and high-end digital projectors can flash even more, according to Thomson researchers. The limit for human visual processing is around 45 flashes per second; above that, a flickering image appears continuous. Furthermore, camcorders do not average frames, as eyes and brains do. Instead, they're sampling devices that take a series of snapshots -- collecting many more frames per second than our visual systems. Hence, frames that eyes would miss show up in a camcorder recording -- and are reproduced on a video screen when the recording is played.

Using extra frames to obscure a recording isn't as straightforward as it seems, however, since camcorders could theoretically be set to a sampling frequency low enough that they'd miss the hidden message, says Zhao. That possibility requires counter-countermeasures, such as randomly adjusting the frequency at which the extra frames appear. Camcorders can't yet adjust their sampling frequencies quickly enough to keep up and produce a quality recording. But camcorder technology will continue to evolve, says Zhao, "and thus, we've got to evolve."

In addition to the frame-insertion technique, Thomson is working on incorporating additional sabotaging mechanisms into its system, such as projecting ultraviolet or infrared light onto the screen and washing out camcorder pictures. Aware that the easy counter-measure to this is simply to place a filter over a camcorder's lens, Zhao says their system is being designed to combine many different wavelengths, so that finding the perfect filter would be difficult.