Chromecast will use ultrasonic sounds to pair your TV with your friend’s phones

Now this is cool: Google’s (S GOOG) Chromecast team has found an interesting way to pair Chromecast streaming sticks with mobile devices that are not on the same Wi-Fi network. Pairing is done through inaudible, ultrasonic sounds, which should make sure that your neighbor won’t suddenly rickroll your TV screen.

Google first announced support for off-network casting at its Google I/O 2014 developer conference in San Francisco Wednesday, and Chromecast Engineering Manager John Affaki said during a presentation at the conference Thursday that the goal was to make the social use of Chromecast in the living room easier.

Google’s YouTube app already allows users to build collaborative queues for on-the-fly YouTube parties, and Affaki said Thursday that the support for these kinds of queues will be added to the Chromecast software developer’s kit to bring it to other apps as well. However, the challenge is that users need to be on the same Wi-Fi network, and sharing Wi-Fi passwords can be cumbersome. “The initial step of getting on the same Wi-Fi network can be really complicated,” said Affaki.

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The new pairing feature will enable users to cast their content even if their phone is connected to a mobile network. To enable this, Chromecast owners have to first allow support for nearby devices. After that, any user in the vicinity of a Chromecast can request from within any cast-enabled app. The Chromecast streaming stick then plays a unique ultrasonic sound through the TV’s loudspeakers. That sound won’t be audible by human ears, but a mobile device in the same room will be able to pick it up and pair with the TV. Alternatively there will also be a four-digit pin displayed on the TV screen, making it possible to manually pair both devices.

The idea of ultrasonic networking was originally conceived by Google engineer Boris Smus, who published an experimental web app using ultrasound for messaging and pairing on his website last year.

Google also announced support for customization of the Chromecast home screen, including personal photos, weather and news content. All of this will come to Chromecast in the coming weeks.

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