TUPM 8.8
`
`COMMUNICATION OF REMOTE CONTROL KEY CODES
`IN THE HOME NETWORK
`
`Mark Eyer
`Technology Standards Office, Sony Electronics
`
`ABSTRACT
`This paper describes CEA-931-A. a standard method for
`communication of Remote Control Unit (RCU) key presses
`across the home audiohideo network. The new standard is
`also applicable where “infrared blaster” techniques were
`previously employed, offering many benefits.
`
`INTRODUCTION
`Technologies such as those built on the IEEE 1394 high-
`speed serial bus protocol are well suited to the delivery of
`high-quality audio and video in the Home Network.
`Methods
`for
`device
`discovery,
`addressing
`and
`encapsulating MPEG-2 Transport Streams within
`isochronous channels on the 1394 bus are well understood.
`Although universal agreement among manufacturers has
`not yet been reached on the methods that would allow the
`user to interact with and control the various devices on the
`network, recent work coordinated through the Consumer
`Electronics Association (CEA) has resulted in a new
`protocol for representation of “basic user intents” such as
`RCU key presses. This paper presents a brief overview of
`the new standard, designated CEA-931-A.
`
`Overview
`In a Home Network, an audiolvideo source device may not
`be located in the same room as the video display device, or
`may be in the same room but not within direct line-of-sight
`of the viewer. To address these concems, a standard
`protocol is needed to allow any device to use the network
`to communicate
`the simple user
`intents commonly
`associated with RCU key presses. This way for example,
`the RCU provided with a digital television could offer a
`PLAY key, and if that key were pressed, the DTV receiver
`would be able to relay that event through the network to
`the currently selected playback device.
`In some scenarios, an “infrared (IR) blaster” approach
`is used to allow one device to control another device. The
`controlling device emulates the IR pulses emitted by the
`target unit’s own RCU. A Personal Video Recorder (PVR),
`for example, can cause the channels on the satellite or
`cable set-top box to change by sending the proper
`sequence of key codes. While usable, IR blasters are
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`0-7803-7721-4/03 $17.00 0 2003 IEEE
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`challenging for a consumer to set up and may be
`unreliable. For a device to use an IR blaster to tune a cable
`set-top box, for example, several numeric keys must be
`sent with proper
`spacing between
`them, possibly
`terminated by an ENTER key. If the keys are sent too
`close together, they may not be properly recognized.
`Further complicating matters, the effects of certain
`RCU keys depend upon the prior state of the device. For
`example, the RECORD command to a VCR or Personal
`Video Recorder will not be accepted if the device is “off’
`(in standby power state). Commands issued using the IR
`blaster method may not always have the desired effect.
`
`THE CEA-931-A STANDARD
`CEA-931-A offers a solution in support of simple IR
`blaster applications, and provides a solution to the general
`problem of communicating RCU commands across the
`Home Network. Figure 1 illustrates a digital television
`receiver connected by a Home Network bus to a PVR. The
`DTV offers a RCU with media control keys
`
`DTV
`
`Room to
`Room
`Interface
`
`Network -
`
`IR pulses
`(proprietary
`format)
`
`“Record
`function’’
`
`PVR
`
`Figure 1. “REC” key example
`
`When the user presses the REC key, the RCU emits
`IR pulses in a proprietary format interpreted by the DTV
`receiver. The DTV recognizes the REC key is intended for
`whatever device the user has currently chosen as the
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`Roku EX1033
`U.S. Patent No. 9,716,853
`
`

`

`source. It packages the key according to the CEA-931-A
`protocol as a “Record function” and addresses it to the
`PVR. The PVR, which also supports CEA-931-A,
`processes
`the “Record function” by unconditionally
`beginning (or continuing) recording.
`
`Summary of CEA-931-A Operations
`Table 1 lists the categories of RCU keys defined in CEA-
`931-A. The standard defines “operation I D codes
`representing all the common RCU keys including the
`arrows and numeric digits, media playback and record
`keys, channel and volume control, as well as keys that
`bring up menu functions. While not reaching the holy grail
`of enabling the “universal” remote, CEA-931-A is a clear
`step in that direction.
`CEA-931-A addresses the shortcomings of typical IR
`blaster
`applications by
`including
`a
`number of
`“deterministic functions” in its repertoire of command
`codes. Whereas certain RCU key presses may toggle the
`target device’s operation between
`two states,
`the
`deterministic functions are specified to be non-toggling,
`,thusLeliminating the need in the controller device to keep
`:track of target device state. These codes include tuning
`functions to allow a controller device such as a PVR to
`directly set the tuner in a source device to a desired
`channel, as well as functions appropriate for control of
`playback and recording. Unattended recording is supported
`oleanly, requiring no special user setup at all.
`A digital cable or terrestrial broadcast set-top box
`supporting the CEA-931-A protocol can be tuned to a
`specified channel number by means of the “Tune
`function.” Other deterministic functions are intended to
`allow devices in the Home Network simple control over
`
`audioivideo source selection and signal routing. Functions
`for selection of AN and audio inputs on compliant AN
`Receivers are provided, as is a function allowing selection
`of a particular disk in a carousel or other multi-disk player.
`For control of device power state, CEA-931-A
`requires compliant devices to respond to the POWER
`control command defined in the AV/C Digital Interface
`General Specification [2].
`
`CONCLUSION
`The new CEA-931-A protocol represents a helpful and
`powerful standard method for representation and delivery
`of RCU keys across the Home Network. It includes
`features specifically designed to support applications such
`the “IR blaster”
`as unattended recording, replacing
`approaches of the past.
`Growing support for the protocol in the industry is
`evident. CEA-931-A was specifically cited in the historic
`in
`digital cable compatibility agreements announced
`December 2002 between
`the cable and consumer
`electronics industries. Cable operators have pledged to
`support it on high-definition digital cable set-top boxes,
`which will also feature an IEEE 1394 port for use by
`consumer digital video recorders.
`
`References
`
`[ l ] CEA-93 I-A Remote Control Command Pass-through
`Standardfor Home Networking, Consumer
`Electronics Association, 2003.
`[2] A V/C Digital Interface Command Set General
`Specification, Version 4.1, 1394 Trade Association.
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