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[Admin: Made title lower-case
(upper-case is reserved for
acronyms) and moved URLs to 'link'
list] |
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Wouldn't people just be able to use
a video camera with an IR filter on
it? |
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An infrared filter does not filter infrared, but allows only infrared through same principle as Sony nightshot but way stronger |
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An alternative method for preventing the illicit videorecording of projected movies might be to design projectors so that rather than flashing each frame on the screen twice, using two rather long flashes, it instead scanned each frame three times from left to right (for a scan rate of 72fps) using a fairly narrow (but bright) stripe. |
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Viewers in the theater wouldn't be likely to notice anything unusual, but video-recorded copies would have ugly vertical or diagonal stripes (the exact nature would depend upon the device). |
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A 30Hz frame-capture camera would have a vertical stripe which was 2/5 the width of the screen, swept across the screen 12 times/second, and was 50% brighter than the rest of the screen. |
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A 60Hz frame-capture camera would have a vertical stripe that was 1/5 the width of the screen, swept across the screen 12 times/second, and was twice as bright as the rest of the screen. |
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A line-scanning camera would have a diagonal stripe (maybe 30 degrees from horizontal) that was 1/5 the width of the screen. swept across the screen 12x/second, and appeared about 50% brighter than the surrounding screen. |
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In the event that 72Hz flicker was annoying to viewers, 96Hz scanning could be used instead. The video artifacts wouldn't be quite as bad (30Hz frame cameras would have a stripe 1/5 the screen width that was 33% brighter than the rest of the screen that would sweep 6 times/second; 60Hz and line cameras would have a stripe 2/5 the width of the screen that was 33% dimmer than background which swept left 12x/second) but they'd likely still be severe enough to make the resulting videos unsatisfactory for most would-be viewers. |
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There are several emerging projection systems, both for digital and conventional cinema designed to prevent camcorder capture through beat-frequency interference or similar. Some of the schemes add watermarking as well. |
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Kodak has a patent on one of them but Sarnoff is researching them as well. |
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// An infrared filter does not filter infrared, but allows only
infrared through same principle as Sony nightshot but way
stronger // |
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That's an IR-pass filter, but IR-cut filters exist too… and just
about every color digital camera already has one built in,
because the colors would look wrong without it! [-] |
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