4 ms·
I'm assuming it would need to be extremely high frame rate video to extreact decipherable voice data. Because even at 60 frames per second, which I understand i
by sopooneo 9y ago
I'm assuming it would need to be extremely high frame rate video to extreact decipherable voice data. Because even at 60 frames per second, which I understand is at the high end for normal video, that gives you a maximum frequency of only 30Hz, which is nearing the low end of human perception.
So it's interesting and a definite risk if an attacker is supplying their own camera, but definitely does NOT mean you can pull voice data from the vibrating tablecloth in a YouTube video, right?
- craigds 9y agoDepends what's on camera and how smart your software is. A full wavelength of audible sound is between a few centimetres and a few tens of metres. If you have a few objects in scene at such known distances, you can calculate how far out of phase they are, interpolate them and piece together a much higher effective sampling rate.
- KnightOfWords 9y agoThey show a technique which exploits the rolling shutter effect to recover frequencies at up to five times the frame rate. On the other hand, they also mention that artifacts in highly compressed video stop their techniques from working, so any secrets in your YouTube vids are probably safe.
- function_seven 9y agoNot from a YouTube video, due to the video compression obliterating the small details needed to get the frequency. But the article notes that a rolling shutter allows even a 60fps camera to capture higher frequencies. Each scan line of the captured video is at a sub-frame time slice. If the object occupies a hundred scan lines, then you have 100 slightly shifted 60 hz samples that you can combine to reconstruct higher frequencies.
- Bitcoin_McPonzi 9y agoDid you read the article? There are tricks you can do that leverage how a rolling shutter works so you can get an effective high framerate across a small area of the image.