scope:

OVERVIEW AND SCOPE

Machine-to-machine control usually involves modeling the behavior of various elements (sometimes called sub-functions or subunits) within audio/video devices. For this discussion, we use the term "unit" to refer to an audio/video component such as a DVD player or satellite settop receiver. Any given unit may include within it one or more different subunits. For example, an A/V Receiver may include audio processing subunits (such as amplifiers and filters), audio/video switching subunits, as well as a tuner subunit.

A unit may include DVD playback functionality for example. A fully-featured machine-machine interface (MMI) to the DVD playback unit would involve a device control model (DCM) of the DVD disk player subunit. Device control models typically support control of all aspects of the device and monitoring of the status of all aspects of operation. Full DCM-based device control protocols are often very complex because many devices are, themselves, complex.

Although it does involve commands sent from one machine to another in the home network, this standard takes a simpler approach to solve a simpler problem. This standard may be used to build a remote control unit that is capable of operating any device in the home network that is compliant with the standard. Traditionally, a so-called "universal remote" is a device that emulates the IR pulses needed to control various devices. It must be configured to emit the appropriate codes, or learn them by sampling the output of a remote one wishes to emulate. With the present standard, the function of the universal remote is accomplished by translating, in a controller device such as a DTV, IR codes received from that device's native remote into standard commands on the network bus. The operations defined here apply equally well to devices in the same room as to devices in other rooms accessible via the network.

We consider a home network to be made up of various types of interconnected Audio/Video devices. Some are sources of A/V data; others take in A/V data and process it for output or display (visual or audio). Some devices in the network may function only to control different devices in the network.

The current standard specifies certain commands sent from one A/V device to another in the home network that represent the kinds of functions that are so basic they are often associated with dedicated keys on the remote control unit. The kinds of functions considered here include such things as power on/off, channel up/down, volume up/down, direct entry of channel numbers, and media playback and record controls (play, pause, stop, fast forward and rewind, record). Operations considered for inclusion here communicate a simple user intent across the network, ideally in response to a single, simple user action. The operation is one of a set of operations that enable a remote control associated with any device on the network with video display capability to perform basic functions on any device in the network.

In the protocol described in this standard, the controller device (the one issuing the command) can know whether the target device has implemented the particular function, and whether it was able to perform the indicated action. In some situations, it is up to the user to know whether the action that was performed was actually the desired action, for example, by visual or audio feedback.

The functions specified here have an effect on the target device that is defined by the manufacturer of that device. As an example, the "POWER" control function corresponds to the behavior that would occur if the user hit the Power key on the target device's native remote. A particular target device may use the Power key as "enter low-power standby" or it may be a power toggle. These functions are used in conjunction with visual feedback to the user, for example via an on-screen display or front panel. A source device can create on-screen displays by embedding text and graphics into its video output. Or, if EIA-775-A [3] graphics are used, the on-screen display can be created from bitmaps delivered across the bus.

This standard does not specify the method a controller device might use to determine which target device on the network should be the recipient of a given command. Typically for example, controllers would send video playback-related command to the networked device currently selected as the video source and audio-related commands (mute, volume control) to the device designated as the audio subsystem associated with that source device.

As several different a/v devices in the room may receive infrared pulses from a given remote control unit, and a controller device may translate these pulses into a network command, a given device may receive both a network-delivered command and that same command in the form of infrared pulses. This standard does not specify design requirements to avoid command duplication in such cases³.

In summary, this standard

• involves network-communicated remote control unit (RCU) commands that convey a simple user intent, usually in response to a single, simple user action;

• does not specify specific behavior required of the target device in response to any given function, although guidance on expected behavior is provided (exact behavior is at the discretion of the device manufacturer); and

• may be used to build a remote control unit that is capable of operating any compliant device in the home network.

³ It is recommended that in the case a target device determines that the same command has been received both via infrared pulses and via the network, it should reply to the PASS THROUGH command with the ACCEPTED response (even if the infrared pulses arrived first).