The Visual Microphone: Passive recovery of sound from video

Wendy

Joined Mar 24, 2008
22,146
Little disingenuous, they require a high speed camera. Surveillance companys can use a laser off a pane of glass to hear what is going on inside, as a passive wiretap. Good luck doing that with a NTSC or PAL system.
 

Thread Starter

MrChips

Joined Oct 2, 2009
21,370
According to the article, the researchers used the horizontal line scan of standard video recording to recover the sound:

Conventional cameras, with a frame rate of just 60 frames per second, cannot be used to extract anything more than extremely low-frequency sounds.

But the researchers came up with a second technique, using the “rolling shutter” typical on digital video cameras, to extract enough information from the video to still recreate high-frequency audio.

Because such cameras don’t save the whole image in one go, but rather record the video line-by-line, far more data can be extracted from it. A simple digital SLR camera, shooting video of a crisp packet at 60fps, can then be used to recreate the audio being played to that packet.
 
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