OK, that's amazing.
By seeing how border pixels on an object fluctuated in color, the group’s algorithm can measure and calculate the object's minuscule movements (and even magnify a wine glass’s oscillations when a tone is played or visually reveal a heartbeat under the skin).
According to Davis, previous ways to recover sound remotely require more than just a video camera. By shining a laser on a vibrating object and measuring how the light scatters or how its phase changes, other researchers have been able to pull out detailed data about the sound.
The team’s processing algorithm lets them take a new tack: a completely passive recovery of the sound. By recording objects’ movements on high-frame-rate video, in ambient lighting—no laser needed—they are able to translate the vibrations caused by speech and music back to sound waves, with only a little bit of noise.
Low frame-rate footage from an ordinary digital camera posed a particular challenge because less signal could get through. But because of the way a “rolling-shutter” camera processes inputs, it could be made to exceed its frame rate and gather enough details to recover comprehensible sounds.
The link includes examples. The standard frame rate is not great, but still, one has to wonder how much can be recovered from existing videos... especially all those politicians having "private" conversations... probably not that much, but still. And the medical uses - having a high speed camera to work out what's happening internally with less need for invasive procedures, maybe ?
https://spectrum.ieee.org/tech-talk/consumer-electronics/audiovideo/your-candy-wrappers-are-listening
Well, it'll probably help the politicians that much of archive footage is lossily compressed.
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