THREE months after the launch of digital TV in Britain, viewers are still
waiting for the new and improved text services that were supposed to bring fast
and easy-to-navigate information pages to their TV sets. And broadcasters still
cannot say when the services will finally be available.
Europe鈥檚 teletext technology is 25 years old. Digital data is added to the
unseen borders at the top and bottom of each analogue TV frame鈥攖he
vertical blanking interval (VBI). TVs with a decoder can receive text and crude
graphics, which is mostly used to carry news, sport and weather services. The
same system cannot be used with digital TV because digital pictures have no
VBI.
Sky TV鈥檚 digital satellite service was launched last October with a modified
system. Sky transmits text data alongside the picture data and an encoder in the
set-top box inserts it into the VBI of the picture it sends to the TV. A TV can
decode this just like normal teletext. 鈥淚t was inconceivable to launch a new
digital service which took something away from the viewer,鈥� says Robin Crossley,
Sky鈥檚 head of new technology. Sky says this old-fashioned approach is just a
stopgap until a new Java-based service called Supertext, which will display
Web-like pages, is launched by Sky鈥檚 partner, British Interactive
Broadcasting.
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But the BBC and digital terrestrial broadcaster On Digital will use a
different Web-like system called MediaHighway, which is taking much longer to
develop than planned. The French broadcaster Canal+ is developing the system,
which is based on MHEG-5, a multimedia format developed by Europe鈥檚 Digital
Audio-Visual Council. But MHEG-5 itself was not ready when the British
terrestrial service was launched, hence the delay.
In mid-February, the BBC and commercial teletext operator Teletext UK were
still waiting for their MHEG-5 software from Canal+, so they have not yet been
able to test a receiver and give On Digital the go-ahead. If and when this
happens, viewers鈥� receivers will be upgraded with software downloaded over the
air. Until then, digital terrestrial viewers will see only a blank screen when
they select a text channel.
MHEG-5 will offer the option of full multimedia with video in a window,
Web-like text and high-quality graphics. The managing director of Teletext UK,
Mike Stewart, says: 鈥淧eople are saying it鈥檚 geriatric before it鈥檚 even born.
It鈥檚 not. It鈥檚 a completely new system which can offer much more.鈥�
Sky鈥檚 Supertext has been developed by sister News Corporation company, NDS of
Israel, whose chief executive Abe Peled warned last year: 鈥淢HEG-5 is an
ill-conceived attempt to re-invent the wheel which I expect to fail . . . Why
develop new tools which are like HTML when HTML is already a standard?鈥�