While the BBC is touting its Project Canvas as the way to bring together broadband and broadcast services, one might be forgiven for assuming that the technical solution has already been specified. The latest version of the Digital Television Group D Book, which describes the standards for digital terrestrial television in the United Kingdom, includes specifications to enable hybrid services, including interactive services delivered over a broadband network connection. The problem is, it is based on an interactive television standard first developed in the mid-nineties with very little reference to the world of the web.

Strategy & Technology, a company which has specialised in developing middleware to support the Freeview platform, says it has been “instrumental in developing a new technical specification to combine the power of the internet with interactive TV”.

Its managing director, David Cutts, chaired the group developing the latest D-Book specification published by the DTG, an industry association for digital television in the United Kingdom. S&ampT is also a founder member of the IMPALA group that promotes the MHEG standard.

“This development provides a new connection giving viewers a seamless experience when using interactive services sourced both from the internet and broadcast TV,” he said.

“We hope that this technology, developed in co-operation with broadcasters, network operators and equipment manufacturers, can provide a simple base from which to develop a whole new range of services for users on digital TV,” said Richard Lindsay-Davies, who heads the DTG.

It is an extension of the MHEG-5 standard used by Freeview and Freesat receivers. As well as interactive applications broadcast over the air, broadband connected receivers will be able to download applications and programming from compatible online services.

S&T says these could include on-demand television services such as iPlayer. Using a standard broadband link, the receiver connects to TV applications and media using internet communications and presents them using technology from the television world.

Therein lies the issue. MHEG-5 is an open standard that was developed before the worldwide web became a mass market phenomenon and owes little to the standards of the internet or modern programming or presentation languages.

MHEG, which stands for the Multimedia and Hypermedia information coding Expert Group that developed it, was part of the DAVIC standardisation initiative to support interactivity and navigation of multimedia services on various small footprint devices.

It always included support for an interactive return path, but at the time this was envisaged in terms of a primitive dialup modem. When Freeview was launched following the failure of the previous subscription terrestrial television platform, the modem was omitted, partly to simplify the proposition and reduce the cost of boxes, but also to ensure that it could not be used to provide transactional services.

“Freeview makes it very hard for any Government to try and make the BBC a pay-television service,” the then BBC director general later wrote in his autobiography, Greg Dyke: Inside Story. “The more Freeview boxes out there, the harder it will be to switch the BBC to a subscription service since most of the boxes can’t be adapted for pay TV.”

However, the MHEG-5 standard employed to provide interactivity on Freeview was extremely restricted in its capabilities and the rather primitive interactive services it enabled, even in comparison to other platforms at the time, were fundamentally limited.

Some of these limitations have since been reduced, for instance to support full colour images on high-definition displays, but the basic declarative description language remains limited and bears very little relation to the standards or capabilities of contemporary computers or web browsers.

MHP was developed as a successor to MHEG, based on the Java programming language. Java itself was originally conceived by Sun Microsystems to support interactive television. Work began on MHP back in 1997.

The MHP standard became embroiled in intellectual property licensing issues, resulting in limited adoption by broadcasters. Nevertheless, it forms the basis of the OCAP specification, now known as Tru2way, that is being adopted by American cable television companies.

The BBC has since largely ignored MHP, although its Research and Development evaluated ways of migrating from MHEG. The prevailing view was that the memory and processor requirements necessary to support Java were too demanding and would increase the cost of receivers. Believe it or not, 16MB of RAM was then considered excessive.

MHP has been nominally adopted as a standard by many countries, but deployments are limited. Meanwhile, led by companies like S&T, a number of territories have adopted MHEG for their digital television services, notably Freeview in New Zealand. Other territories, like Australia are also looking to the success of the Freeview platform in the United Kingdom, although they may be having second thoughts about adopting MHEG.

The concern must be that in extending MHEG to enable hybrid broadband and broadcast services, broadcasters are building on a specification first conceived over 15 years ago. It is little understood beyond a relatively small circle of developers and bears little relation to the standards that are widely adopted in the world of the web.

Consequently, it will be difficult to exploit the vast pool of capabilities that have been developed based on internet protocols. The risk is that hybrid broadband and broadcast services developed on this standard will be hobbled by the limitations of the platform.

Furthermore, there seems little prospect that standards based on MHEG will ever be interoperable with those used on other television platforms. Although there have been attempts to create a common description language that can work across different technologies they have yet to gain any real traction.

Arguably, all that is required in order to support the delivery of on demand services across multiple platforms is a specification of the media formats to be employed and common agreement on the metadata by which programming can be accessed.

While a client could be created based on MHEG, this should not preclude the possibility of one based on MHP, Open TV, WTVML, Liberate, or indeed the standards and technologies widely deployed on the web.