updated 07:10 am EDT, Fri June 27, 2014
Engineer explains Google Chromecast pairing using unhearable sounds
The Google Chromecast apparently uses ultrasonic sounds to communicate with mobile devices that are not located on the local network. Revealed during a presentation by Chromecast Engineering Manager John Affaki at Google I/O yesterday, the streaming HDMI dongle will apparently play a unique ultrasonic sound via the television's speakers in order to identify itself to an unknown device.
The ultrasonic pulse will be picked up by the mobile device, in order to ensure the smartphone or tablet is in the immediate vicinity, reports GigaOM. Once support for nearby devices is enabled on the Chromecast itself, it will start transmitting the sound, which cannot be heard by humans, while a back-up PIN will also be available if the TV cannot transmit the sound or the host device cannot hear it. It is believed the nearby device will remain off the local network, and will transmit its video or audio programming selections through a different open Wi-Fi or cellular Internet connection to Google, in turn sending the request back to the Chromecast.
Pairing of off-network devices was one of a few features said to be coming to Chromecast in the future. The option to personalize the standby photo feed to include images from multiple sources will be available, as well as support for screen casting from Android devices, allowing for the display of a smartphone to be shown on a nearby television.