Finnish Hacker Isolates Helicopter GPS Coordinates From YouTube Video Sounds

An anonymous reader sends a post by Finnish electronics hacker Oona Räisänen, who heard a mysterious digital signal in the audio accompanying a YouTube video of a police chase. The chase was being filmed by a helicopter. Räisänen wrote: "The signal sits alone on the left audio channel, so I can completely isolate it. Judging from the spectrogram, the modulation scheme seems to be BFSK, switching the carrier between 1200 and 2200 Hz. I demodulated it by filtering it with a lowpass and highpass sinc in SoX and comparing outputs. Now I had a bitstream at 1200 bps. ... The bitstream consists of packets of 47 bytes each, synchronized by start and stop bits and separated by repetitions of the byte 0x80. Most bits stay constant during the video, but three distinct groups of bytes contain varying data." She guessed that the data was location telemetry from the helicopter, so she analyzed it to extract coordinates. When she plotted them and compared the resulting curve to the route taken by the fleeing car in the video, it was a match.

Comments

Brilliant hack!

[HellCatF6]

There was a time, before we all lost our minds to Pong, Asteroids and Zelda (yes, I go way back) where we also spent time taking our world apart and figuring out how to make it better.

Oona rocks! She should be rewarded somehow.

BTW - the end of the article finally explains how a megahertz signal found its way onto the audio track.

Finally!

[ArchieBunker]

A story worthy of slashdot. Please post more of these (not being sarcastic).

Re:Am I missing something?

[Rosco P. Coltrane]

So what? It was still fun, as in "this Youtube video contains more data than meets the eyes. Let's find out what it is."

As a ham radio enthusiast, I get the same pleasure decoding the bits of morse code that can be heard in movies from time to time: usually it's pretend morse code, but once in a while you hear a bit of a real transmission that's been overlaid onto the soundtrack by the sound engineer who didn't have a clue that what he used actually meant something totally unrelated to the movie.

In fact, I heard a CQ call followed by a callsign in a scifi B-movie from the 90s once, and sent a QSL card to the owner of the callsign in question. He answered me saying I was one of only 5 people to have done so over the years. How fun is that?

So yes, the code is known, there's nothing special about it, but she had fun digging out unexpected information, and I had fun reading about it. Stop being so jaded.