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link: Chromecast Now Lets Your Guests Take Over Your TV Without Needing Your WiFi Password
Back in June, Google announced a rather nifty new feature coming to Chromecast: your friends and house guests would soon be able to connect to your Chromecast without being on your WiFi network, thanks to the clever use of magic ultrasonic sounds.
after a few months of silence, that feature launches.
One bummer of a caveat, though: it’ll only work if your friend’s phone is running Android, for now. Why? It all comes down to that age-old problem: iOS apps aren’t allowed to do certain things required to make it work, so they’re rolling with it on Android until that changes.
Guest mode is off by default. Flip it on, and your Chromecast will start displaying a PIN on its idle screen. Meanwhile, your TV will start emitting ultrasonic sounds, inaudible to the human ear*, which Chromecast-enabled apps on your phone will be listening for. When the two find each other, everything falls into place and the pairing is made.
[* No word yet on if non-human ears (i.e. dogs) can hear it. If your dog starts whining whenever your Chromecast is on, you should probably turn guest mode back off.]
(Score: 0) by Anonymous Coward on Friday December 19 2014, @12:03PM
As I understand it, the TV needs to be built specifically for this system anyway, so I'd expect those TVs also to be built to be able to emit those high-frequency sounds. Probably they are added in after the TV sound passed those filters (after all, you don't want high frequencies in the TV sound to disturb your intentional ultrasound signal), and the speakers are built to handle those. Alternatively, the TV could get a small extra speaker specifically for the ultrasound. Note that due to the high frequency, ultrasound speakers may be quite small.
If the TV has also a microphone built in, I could also imagine that the TV could be hacked to use this ultrasound emission as surveillance device (remember, bats use ultrasound to "see" their surroundings; there's no reason a TV with ultrasound emission capability shouldn't be able to do that, too).
(Score: 2) by cafebabe on Saturday December 20 2014, @07:50PM
Echo-location with a single microphone is a fanciful element of a Batman film (The Dark Knight Rises?). Regardless, a single microphone in a telephone or television is ideal for surveillance, even if it sampled at a low frequency.
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