The Digital Audio-Visual Council (DAVIC) has issued a draft technical specification to support a wide range of applications using emerging digital technologies, such as broadcasting, video-on-demand, tele-shopping and other interactive services.

This draft specification embodies agreements reached by some 270 experts from all over the world during a 5 day meeting in Melbourne hosted by Telstra (Telecom Australia).

The goal of DAVIC is to promote global standards for broad-band digital services using a variety of delivery media such as the "information super-highway" or satellite broadcasts, ensuring compatibility and inter-operability on a world-wide basis. This will be advantageous to all parties - equipment manufacturers, network operators, content producers, service providers and consumers.

Leonardo Chiariglione, the President of DAVIC, said "This is a major achievement which will accelerate the introduction of advanced multimedia services. It could not have been achieved without an unprecedented degree of co-operation between all parties."

DAVIC is a not-for-profit organisation registered in Geneva, Switzerland. In less than one year, DAVIC has reached a membership of more than 150 organisations from 20 countries throughout the world, representing virtually all interests in emerging digital audio-visual applications and services. DAVIC is working closely with international standards organisations, such as the ITU and the ATM Forum.

The specification (DAVIC 1.0 Rev. 3) consists of almost 500 pages. DAVIC is now soliciting comments on the specification from all interested parties - whether they are members of DAVIC or not. The specification has been "frozen" in the sense that changes will be made only if there are inconsistencies or demonstrated inadequacies. Inter-operability tests will be conducted in at least three locations (North America, Europe and Japan) in the next few months. The next meeting of DAVIC will be held on 11-15 September in Hollywood, USA. The specification will be finalised by DAVIC at its meeting to be held on 11-15 December 1995 in Berlin.

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DAVIC specifications are intended to define unambiguously a complete end-to-end system capable of providing a wide range of services which include broadcasting, video on demand and highly-interactive applications such as home shopping. The specifications are complete in that they define all interfaces between system components, including set-top unit, delivery systems and servers, from the physical level all the way through to the application level. The nature of specifications is such that systems built in accordance will not only provide the required functionality but can also be constructed of elements which are interchangeable on a worldwide basis. Such worldwide inter-operability is essential in stimulating the development of applications which can be offered to the public on a global basis. Additionally the specifications are so constructed that a multi-vendor environment is enabled and individual vendors are empowered to develop their own unique implementations of system components.

Because DAVIC specifications are at the forefront of a rapidly developing field, the need for rapid deployment has to be balanced against the possibility of introducing new technology in the future. Therefore DAVIC specifications define the technical "tools" whose use allows the provision of functionalities required by digital audio-visual systems and the applications that make use of them. Tools are usually associated with grades that determine the level of performance of a given tool, e.g. mono/stereo/multichannel audio, TV/HDTV, or bandwidth of a return channel. As time goes on more grades of tools or brand new tools can be introduced. The toolkit nature of DAVIC specifications would lead to too many incompatible instances of subsystems if not accompanied by the definition of groupings of tools with associated grades - called profiles. Profiles are defined so as to minimise their number yet be able to span a broad range of uses.

Specifications contain a general description of functionalities, the reference model of the entire system and of its functional components, all protocols and modulation schemes used in the different parts of the system, the precise definition of reference points and interfaces, and the adopted profiles.

Among the key agreements documented by the specifications are the modulation schemes needed for delivery of information encoded according to DAVIC specifications on hybrid fiber coax (HFC), fiber to the curb (FTTC), satellite and twisted pairs at both long and short ranges. Protocols adopted by DAVIC include elements of MPEG-2, the DSM-CC (Digital Storage Media Command and Control, part 6 of MPEG-2), the RPC (Remote Procedure Call) defined by OMG (Object Management Group) UNO (Universal Network Object) with IIOP/GIOP, AAL5 (ATM Adaptation Layer) and Q.2931 for ATM signalling.

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