Consumers could be excused for being skeptical about the rapid succession of innovations that are being launched on the market. Their many new functions undoubtedly have the potential to offer an enriched home audio/video experience. But installing them and connecting them together can be a problem, especially with the increasing move to digital technology.

Recognizing the need to simplify the installation and operation of new digital home devices, eight of the world's leading consumer electronics manufacturers have collaborated to develop the Home Audio Video Interoperability (HAVi) standard. Grundig, Hitachi, Matsushita (Panasonic), Philips, Sharp, Sony, Thomson and Toshiba all plan to license the architecture that they have developed to the electronics and multimedia industries. Philips will handle licensing contacts on behalf of the eight companies.

But what are the benefits for users? Well, they are quite significant in a number of ways. Take installation, for example. Installation for digital devices often involves more than just connecting up the cables. In many cases it is also necessary to adjust settings-such as addresses, for example-so that devices can "find" each other on the network. With HAVi, this is all done automatically; no user intervention is required. A device can be added to or removed from the network at any time, and the appliances will automatically communicate with each other, recognize changes in the network configuration, identify the available functionality and its location, all without interrupting the functioning of the network.

There are also some important benefits where operation is concerned. The main change is that devices will be able to share their resources across the network. All HAVi-compliant devices will automatically register their available functionality and make it accessible to other devices. What will that mean in practice? Users need only indicate the function they want to perform. They will no longer have to worry about where that function is located or input commands to several different devices.

In addition, the user interface of the device they wish to access can be presented remotely-for example, on the screen of a TV set connected to the network. This feature enables users to interact with any HAVi-compliant function using any device on the network that has a display capability. This display device need not be aware of the functionality behind the user interface it is displaying; the device is simply offering its display to another application.

To take a simple example that will be easily recognizable for many people, doing a video recording requires making the settings on the VCR itself. It has to be set to the desired channel and the recording has to be started or a later start time entered. But what if the VCR is in a different room, and the user wants to make a recording immediately of something that is being shown on TV? With HAVi, this is no problem, because all it takes is to enter the "record" command with the remote control. All the necessary actions are taken by the system.

In this situation, the TV can automatically program the VCR using data obtained from the Electronic Program Guide, which is received by the TV. The VCR can automatically set and update its own time based on the clock of the TV, which is set by a satellite receiver or other broadcast source. If the VCR is disconnected the TV will notice this, and will inform the user that programmed recordings are no longer possible. It can also search the network to find another, connected VCR and use that one instead, thereby transparently delivering the functionality that the user originally requested even though changes have taken place in the network configuration.

Clearly this is a relatively simple example, and there are a lot of situations involving more complex interactions between more widely differing devices. What about a TV that has a voice recognition capability? Maybe one that's even connected to a video telephone link, so that the TV is muted and calls are answered automatically by a voice command? Or a video camera that automatically displays a picture on the TV screen when a visitor arrives, or starts a recording if the same thing happens unexpectedly during nighttime hours? Or intelligent audio/video storage devices that auto- matically deliver content of a type requested by the user at a specific time?

It is important to emphasize that HAVi is a consumer electronics technology, aimed primarily at devices with high-quality audio/ video and multimedia capabilities.

For this reason, the IEEE 1394 (Firewire) standard has been chosen as the interconnection medium of choice. The selection of IEEE 1394 is a logical one, because that standard is able to handle high communication bandwidths, which are typically the case with high-quality audio and-especially-video applications.

Real-time streams

This is an essential requirement for HAVi, because of the need to play streams of audio and video material in real-time-in other words, the moment of delivery from a broadcast source or local storage medium. IEEE 1394 also offers other important capabilities for the home network environment. These include full-duplex operation, which means that data-in the form of audio/video signals and control commands-can flow between devices in both directions at the same time. Other relevant features of IEEE 1394 include its hot-plugging and self-configuring capabilities, as well as its ability to transfer both isochronous data streams (streaming audio and video) and asynchronous commands at the same time and over the same interface.

All of these features provide the right basis for a truly interactive network in which users can access more than one function at once, all using the same cabling infrastructure.

And even though HAVi primarily targets consumer electronics appliances, it can be extended to many other classes of devices. In fact, HAVi is independent of any particular operating system or CPU and can be implemented on any platform, ranging from embedded environments to Windows or Unix systems. This means that a PC can also act as a HAVi device, with the ability to participate in a HAVi network, control other connected devices and offer audio/video-related functionality that can be accessed by the other devices on the network.

Under HAVi, the communication between devices is based on platform-independent messaging systems and uses Streams Manager, which can carry several different data streams at the same time. This technology handles the identification of available device functionality-for example, whether a display operates in DV or MPEG format, or whether a speaker system expects to receive AC3 or MP3 data.

Also important is that HAVi is a multibrand standard. This means that HAVi-compliant devices, regardless of brand, can be connected to a home network and will offer all the HAVi benefits together with the other connected equipment. This is achieved by incorporating software elements defined by the HAVi standard that are common to all appliances. A further benefit of this standardized approach is the creation of an open and future-proof concept. New, compliant devices can be added to a system at a later time, which protects the user's initial investment in equipment.

What happens when we want to make a connection with other locations? HAVi also has the answer for situations like these. A bridge is being created to the Jini distributed-network architecture developed by Sun Microsystems Inc. In contrast to HAVi, Jini focuses primarily on computing devices, peripherals and impromptu systems. It allows products to access services across distributed networks. Like HAVi, Jini offers conveniences such as easy plug-and-play connectivity and brand-independent interoperability.

In a move to give users the best of both worlds, Philips, Sony and Sun have developed a bridge between the worlds of HAVi and Jini, linking HAVi-compliant digital appliances in the home to services provided across Jini-based distributed nets.

The HAVi/Jini bridge adds an extra dimension to HAVi's network-interoperability concept by enabling applications, services and content to run seamlessly between Jini and HAVi-enabled products. It will make it possible to send instructions by e-mail to a connected home appliance-whether it's a video recorder, cooker or whatever-from a place of work or any other location where a remote application can be accessed.

Besides accessing digital audio/ video appliances in the home from remote locations, the bridge will also do the opposite: allow those appliances to access distributed services and resources, regardless of location, via the network. Not only can digital data streams be processed from "native" consumer electronics devices like set-top boxes, satellite decoders, cable modems, digital video recorders and DVD-Video players, but HTML-format data and images retrieved from the Internet can be accessed. For this job, HAVi will have a special Web API that allows devices to access the Internet without the need to support the Internet Protocol in every HAVi device.

In the same vein as the HAVi/Jini bridge, work is also being done on bridges to other network architectures, such as HomeAPI. With its focus on devices in the control and automation areas, such as lighting, heating and security, HomAPI is centered on Windows-based applications. The bridge will add benefits through the complementary features of the two networks.

The eight participating manufacturers are confident HAVi will meet a real market need in those applications for which easy and transparent operation is the primary requirement; in other words, those related mainly to audio/video entertainment in the home. At the same time, the standard has enough inherent expandability to future-proof it against new needs and functionalities as they arise.