A change to CEA-861 takes time, and then you need new products in homes.

Jeffrey KraussThere is a lot of effort underway in the cable and consumer electronics industries to develop methods for conserving energy. Some of this is driven by the Energy Star 3.0 requirements for TVs, DVD players and set-top boxes. But energy conservation could be enhanced if these connected devices could trade status information, so that a cable box could go to “sleep” when the viewer is watching a DVD movie.

The SCTE has created a new standards subcommittee, the Sustainability Management Subcommittee (SMS), to work on energy efficiency requirements for products used in the network, such as computers and servers, transport equipment, and power supplies. Future work might include adaptive power systems, where variable energy consumption needs would be based on network traffic and transactions within the network.

The NCTA and CableLabs have just announced a new initiative toward improving the energy efficiency of consumer STBs and other devices. Some of this effort will focus on capabilities to reduce power consumption when subscribers are not actively watching television. So the concept of adaptive energy consumption limits has worked its way into consumer premises equipment.

The Consumer Electronics Association has had work underway for several years to define methods for measuring energy consumption by TV receivers, DVD players and set-top boxes. This work includes the notion of three energy states: “on,” “off” and “standby.” For a set-top, the standby state might be understood as one where the box is not supplying audio and video output but may be communicating or exchanging data with the headend.

The draft Energy Star 3.0 specification for set-top boxes takes this further, to include “sleep,” “deep sleep” and “automatic power down” modes of operation.

The Energy Star 3.0 specification sets energy usage limits for set-tops. The basic limit for cable set-top boxes is 60 kilowatt hours per year (kWh/yr). But there is an additional allowance of 25 kWh/yr for HD and 15 kWh/yr for a CableCard, for a total of 100 kWh/yr. For a cable box that is “on” all of the time, that works out to 11.4 watts. The fairly new box that I use at home, the one without the DVR, draws 15 watts. It never goes into a low-power “sleep” mode. So its total annual energy consumption is 131 kWh/yr.

The Energy Star specifications were established with a usage model that assumes 14 hours of “on” a day and 10 hours of “sleep.” So if my STB had a sleep mode that drew, say, 5 watts, I calculate that the total annual energy usage would be 95 kWh/yr, meeting the Energy Star requirement.

But cable STBs today don’t typically go into sleep mode. A TV receiver can have a sleep mode – when the display is turned off. A DVD player can have a sleep mode – when there is no disk in the player. A set-top box only goes into sleep mode if the user turns the box “off” … but nobody turns off their STB.

A STB could, in principle, go into sleep mode if the TV display is turned off, or if the user is watching a DVD. But with today’s technology, there is no way for the STB to know when the TV display is off or is displaying the DVD rather than cable programming.

It doesn’t have to be that way. A few months ago, I attended a talk by Bruce Nordman of Lawrence Berkeley National Laboratory, who has been working on energy conservation issues for years. He highlighted the inability of devices in home networks to optimize energy consumption because they do not have knowledge of the activities of other devices in the network.

But he failed to propose a solution. So I’m proposing a solution, at least for the simple case of a digital TV receiver with two HDMI connectors and two devices (a cable STB and a DVD player) connected to them.

CEA-861 is the industry standard that defines the handshaking messages that are passed over the HDMI interface. Today, these messages mainly convey the abilities of the TV receiver to display video and decode audio, and the abilities of the signal sources (STBs and DVD players) to deliver signals compatible with the TV receiver.

CEA-861 is a living standard. It has been extended several times, and it could be extended again. The two-HDMI TV receiver could send a message to the two signal sources that says: “I’m displaying a signal from HDMI-1,” or “I’m displaying a signal from HDMI-2” or “My display is turned off.” Or maybe the message should be: “I’m displaying your signal” or “I’m not displaying your signal.” So the cable STB could go into sleep mode when it learns that the TV display is either turned off or is displaying the DVD signal.

Of course, a change to CEA-861 takes time, and then new products would have to work their way into homes. But we need to start somewhere.