Will Digital Cinema Can Pirates?

By Seán Captain | Also by this reporter

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

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

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.

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