Will Digital Cinema Can Pirates? By Seán Captain | Also by this reporter http://www.wired.com/news/technology/0,69922-0.html?tw=wn_tophead_2
Switching from film-based to digital projectors in movie houses promises better quality for theatergoers. But it could also help Hollywood studios nab bootleggers. Digital projectors can't stop people from recording movies, but they can allow studios to trace every illegal copy back to the specific time and theater where it was recorded. This capability is a requirement of the Digital Cinema System Specification -- the playbook for digital theaters in the United States and potentially worldwide. This approach isn't entirely new. Studios often embed tracking information in prints. "They don't publicly talk about this," said Brad Hunt of the Motion Picture Association of America, "but it's a well-known fact that forensic watermarking is being used on theatrical release prints because that's how we can determine sources of piracy." Data in prints, however, can only say what reel of film was copied. Because digital projectors add the information as the movie is playing, they can specify when the piracy occurred. "We now can actually extract the data that the content was rendered at 2 a.m.," said Hunt, giving a hypothetical example. The digital projection guidelines, published in July by a consortium of Hollywood studios called the Digital Cinema Initiatives, say every five-minute chunk of video must contain a 35-bit "forensic marker" specifying the date, time and location at which the movie is shown. The guidelines don't say how to get that information into the movie, but they require it to be "visually transparent to the critical viewer" and "inaudible in critical listening" tests. One way is to include tones that are outside the range of human hearing. "That's old tech," said Brian Claypool, spokesman for Christie Digital Systems, a major maker of cinema projectors. "It doesn't give you a lot of information." It's also possible to speed up the image refresh rate and insert extra video frames. Hunt said that method is used to ruin the quality of bootleg copies. Although the frames flash too quickly for viewers to notice, the image sensor in a video camera picks them up. Such a trick could also be used to encode tracking information. But Hunt said several other techniques exist. "We're not trying to describe specifically what is being done, because the effectiveness of these technologies is based on a lack of knowledge." Claypool also declined to say what cues Christie projectors add to the video. But he said they meet the requirement of being able to survive changes to the copy, such as recording it at a low bitrate, altering the resolution or converting it to a different file format. "No matter how low-quality it may be, you can trace it back to the source," said Claypool. Christie will be supplying equipment with the tracking technology for a movie studio- and distributor-funded program to place 4,000 digital projection systems in U.S. theaters by the end of 2007. The effort is a baby step, however. About 30,000 movie theaters show films in the United States and about 100,000 globally -- completing the transition could take decades. You are a subscribed member of the infowarrior list. Visit www.infowarrior.org for list information or to unsubscribe. This message may be redistributed freely in its entirety. Any and all copyrights appearing in list messages are maintained by their respective owners.