One of the promises of the digital revolution is to create increasingly intelligent consumer electronics (CE) devices and systems that can automatically configure themselves, correct errors, and free the user from having to manage them. HDMI
provides the framework for delivering on this promise, not only by drastically simplifying cabling, but by establishing a structural basis for system-wide intelligence.
The promise of Consumer Electronic Control
The optional Consumer Electronic Control (CEC) feature of the HDMI specification offers a powerful opportunity for system-level automation and unmatched ease of use when all devices in an entertainment system are equipped to support it. For example, when viewing content on an HDTV, a CEC-enabled HDTV remote could be used to play or rewind movies, manage power-on, input selection, and power-off functions for the TV, set-top box, and audio/video receiver, switch inputs and outputs, or change video and audio modes.
The HDMI standard requires manufacturers to disclose specific HDMI features that are enabled in a product. For each feature, the guidelines specify a minimum level of functionality that must be met by a device in order to use the terminology. The idea is to provide consumers with the necessary descriptive information they need to understand enabled features that take advantage of certain advanced capabilities of HDMI, such as CEC functionality.
While HDMI LLC Authorized Testing Centers (HDMI-ATCs) test for CEC electrical parametric and protocol compliance against the HDMI CEC specification, there is a need to build upon this basic testing with additional performance testing programs designed to simplify consumer purchase decisions and enhance the high-definition entertainment experience. At the HDMI-ATC level there are no Remote Control and User Interface operational performance compliance specifications, testing requirements, or test tools designed to ensure accurate end-to-end CEC performance delivery.
Figure 1: Example of One Touch Play operation
CEC functionality promises the consumer the ability to use a single remote control to operate multiple CEC-enabled HD devices, eliminating the need to juggle separate remotes to control the TV, set-top box, portable HD devices, etc. Manufacturers have a long list of optional CEC commands to choose from, as well as the ability to implement their own vendor-specific commands on top of the more standardized commands. However, all properly executed HDMI devices with the optional CEC feature are required to support a minimum, baseline set of CEC functions. For example, an HDTV device described as supporting CEC must be capable of accepting CEC commands, processing the commands, and taking appropriate functional action.
One Touch Play
One of the most commonly expected applications for CEC is One Touch Play. The consumer pressing the "Play" button on a DVD player issues a command to a downstream A/V Receiver to automatically power on, switch to the active HDMI input, and similarly send the same power on and input switch commands to the HDTV. This type of functionality typically requires a series of buttons to be pressed on three or more remote controls, but with CEC it can be accomplished with a single button press (Figure 1).
Another example is when a set-top box's tuner commands (e.g., channel up, channel down, channel number input) can be issued by any remote of any CEC attached device, such as a HDTV. More specifically, the HDTV's remote control can perform these commands without having to be programmed with the set-top box's specific brand information.
Yet another CEC functional example is the "Remote Control Pass Through" application. Some home theater systems place the HD components in a cabinet with doors that are opaque to IR commands. Existing work-arounds use additional, external devices to retransmit IR commands to areas that do not have line of sight to the remote control. The CEC channel in this case can be used to issue a command, such as "channel up," via the TV's remote control, and route it to the blocked device without the need for a work-around solution.
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