The Visual Microphone: Passive recovery of sound from video


Joined Mar 24, 2008
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


Joined Oct 2, 2009
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.