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Video pirates who use digital camcorders to film movies in the cinema now
have another obstacle to overcome. Current systems try to defeat piracy by
varying the rate at which frames are displayed on the cinema screen, but pirates
have learned to program camcorders to keep in step. So Digital Electronic Cinema
of Los Angeles wants to beam 20-microsecond pulses of infrared into the audience
during public screenings (WO 0074366). The inventors say that audiences will not
notice the pulses, but they will overload the camcorder’s light sensors and
spoil the recording.