Chromecast’s secret weapon to take over your TV: HDMI-CEC

Chromecast, Google’s (s GOOG) new TV dongle that is meant to beam online videos straight from your laptop or mobile device to your TV, comes with a nifty feature that was only mentioned briefly during Wednesday’s announcement: Users will be able to turn on their TV, switch inputs and automatically start playback just by pressing a single button on their mobile device. The technology that makes this possible is called HDMI-CEC.

HDMI-CEC is an extension of the HDMI display port interface that makes it possible to send control commands back and forth over an HDMI cable. The idea behind HDMI-CEC is to simplify the use of multiple devices connected to each other via HDMI. It can, for example, be used to control a DVD or Blu-ray player with your TV’s remote control, or even change the volume of your home theater receiver with that same remote.

HDMI-CEC was first introduced with HDMI 1.3, and is now supported by numerous TV sets. However, to make things more complicated, manufacturers have decided to promote the feature under a multitude of names, including Anynet+ (Samsung), Bravia Link and Bravia Sync (Sony), Simplink (LG), Viera Link (Panasonic) and Regza Link (Toshiba).

In most cases, HDMI-CEC is used to send commands from the TV set to other devices, but the data can flow both ways, and Chromecast uses HDMI-CEC to control the TV set from the dongle.

It’s a pretty simple feature, but it solves a problem that manufacturers of connected devices have been struggling with for years: getting the users to switch inputs on their TVs just to access a streaming box is a major show stopper, which is why Google TV, Xbox (s MSFT) One and others have been trying to become the default choice by piggybacking on the TV signal.

At least in the case of Google TV, this approach hasn’t really been all that successful. Giving the device itself the power to switch the input and power on the TV may just be one of those things that seems insignificant at first, but could become a killer feature once it’s in the hand of consumers.