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IN THE EARLY summer of 1889, George Eastman, founder of the Kodak company,
provided Thomas Edison with the first batch of film for his experiments
with a cinema camera and projector. One hundred years later the electronics
industry is gunning for film. It wants to replace film with magnetic tape
that can reproduce more cheaply and more conveniently the same high-definition
pictures, or images of great clarity and detail, on giant TV and cinema
screens. The commercial prospects for the new medium are enormous.

Industry has started modestly by concentrating on the production of
high-definition television (HDTV). Although its achievements have been impressive,
the development seems unlikely to trouble Kodak, the company that still
corners the market for raw film stock, for some time yet. The reason is
that broadcasters and manufacturers cannot agree an international standard
for HDTV. This has caused confusion and a power struggle with three major
contenders: the industries of Japan, Europe and the US. But as Europe squabbles
over standards and the US prepares to evaluate more than 20 competing systems,
Japan is already planning the public transmission of its very own brand
of HDTV.

The idea of replacing the chemistry of film with the electronics of
TV is not new. The British government made the very first move towards HDTV
in 1943 when it appointed a committee under Lord Hankey to consider the
future of television. Hankey recommended the development of a new system
‘to approach the cinema standard’.

Before the war Britain had adopted a TV system that displayed 25 pictures
a second: an electron beam built up these pictures from 405 ‘horizontal
scanning lines’, which it created by sweeping across the back of the screen
from top to bottom. Twenty-five pictures a second is fast enough to create
the illusion of smooth motion (a cinema displays 24 pictures a second),
but too slow to prevent the eye from perceiving a flicker of light between
each display. The answer was to increase the rate of display, which was
done most conveniently by showing every picture twice. In the cinema, a
shutter interrupts light in the projector 48 times a second and flicker
is cut out. TV got round the problem, and still does, by splitting a picture
into halves, made up of alternate scanning lines. These two sets of ‘half-scans’,
or fields, are transmitted alternately and interlace so rapidly on screen,
50 times a second, that viewers never realise they are watching only half
the picture at any one instance.

The British system was very good for its time, but it provided only
black-and-white pictures and 405 lines could not match the definition of
35-millimetre film. ‘We think that television definition should eventually
be of the order of 1000 lines and that the introduction of colour and stereoscopic
effects should be considered,’ advised the Hankey committee.

Britain never followed through, however, and lost its lead in TV technology.
In the 1960s, along with most of Europe, Africa, mainland Asia and Australia,
Britain adopted a colour system called PAL (Phase Alternate Line). This
increased the number of lines a picture to 625, which still interlaced 50
times a second. It was the best system at the time. The US and Japan had
previously adopted the NTSC (National Television Standards Committee) system,
based on 525 lines and 59.94 fields a second. American engineers chose this
bizarre figure, which has been a thorn in the side of the electronics industry
ever since, to forestall interference on colour transmissions caused by
fluctuations of America’s electric mains supply, which is distributed at
a frequency of 60 cycles per second. (For convenience, the NTSC system is
usually said to display 60 fields a second.) By the time of the introduction
of PAL, manufacturers were producing TV sets that were independent of the
electric mains supply.

The number of horizontal scanning lines on a TV screen limits the quality
of the picture it displays. Better pictures demand more lines and wider
screens, but this requires the transmission of higher frequencies because
the signal must change more rapidly to convey the extra information. The
problem is that the higher the frequencies, the wider the spread of frequencies
from low to high, or bandwidth, that must be transmitted. Conventional TV
signals use a 6-megahertz bandwidth, while wide-screen pictures with over
1000 lines will need a bandwidth of 25 or 30 megahertz. But engineers cannot
simply broaden the transmission band: for a start our airwaves are already
overcrowded. Instead, they must invent a new transmission technique.

The Japanese state broadcasting station NHK, Nippon Hoso Kyokai, started
research on HDTV in 1970. NHK saw HDTV both as a replacement for film, which
comes mainly from Kodak in the West and is an inconvenient medium that cannot
be reused, and as an improved transmission system, which would create a
market for new receivers.

NHK’s engineers spent 10 years testing a wide range of systems before
deciding that the best compromise was a picture with 1125 lines, interlacing
60 times a second. NHK also discovered that viewers would prefer a wide
screen, and so it increased the ratio of width to depth of the picture,
known as the aspect ratio, from 4:3 to 5:3. The company subsequently developed
a technique called MUSE (Multiple Sub-nyquist sampling Encoding), which
compresses the 30-megahertz bandwidth of the signal to around 8 megahertz.
Like most compression systems, MUSE transmits only the changing parts of
a picture. The receiver has memory chips that store any stationary picture
information, which it uses to reinforce detail. The penalty is that moving
objects appear less clear on screen than stationary ones because there is
nothing stored to reinforce detail in motion.

Sony was the first Japanese electronics company to back NHK’s work.
Since 1984, it has sold hundreds of high-definition video recorders, cameras
and monitors to production studios around the world to use instead of 35-millimetre
film equipment. All the major electronics companies in Japan have joined
Sony to develop HDTV equipment under the generic name Hi-Vision. By the
early 1990s Japanese satellites will be transmitting HDTV signals directly
into homes. With their domestic market sorted out, Japanese manufacturers
are now eyeing other territories.

Europe’s answer to Hi-Vision is a project under the EEC’s Eureka programme,
which promotes collaboration in the field of advanced technology. The research
project, which began in July 1986, gathers together 30 European electronics
companies, research laboratories and broadcasting authorities. With this
scheme, Europe is trying to do what Japan has been doing for years – get
rival companies to cooperate so that they can compete as a group against
foreign industries.

The plot thickens

Eureka shares a common aim with the Advanced Compatible TV (ACTV) system
that the David Sarnoff Research Center is testing in the US: it wants to
develop an HDTV system that is at least partly compatible with existing
domestic TV systems. (This will save broadcasters having to record and transmit
two signals; one for existing sets and another for HDTV receivers.) The
penalty is that this makes incompatibility between the Eureka and ACTV systems
inevitable, since the standard American TV picture has 525 lines interlacing
60 times a second, while a European picture has 625 lines interlacing 50
times a second.

To complicate the issue, there is another major difference between the
two systems. Whereas the ACTV system builds on the standard American format
NTSC, the Eureka system builds on modified 625/50 technology that has been
developed for satellite broadcasting into European homes.

The Independent Broadcasting Authority in Britain developed a system
called MAC (Multiplexed Analogue Components), which takes advantage of the
wider bandwidth available on satellite channels, up to 12 megahertz, to
give clearer pictures from 625 lines. Satellites can broadcast signals of
a wider bandwidth because they use the uncrowded ‘microwave’ bands of around
10 000 megahertz, instead of the crowded ‘ultra-high frequency’ bands of
below 1000 megahertz, which terrestrial transmitters use. With forethought
worthy of the long-forgotten Hankey committee, the IBA’s engineers began
to design MAC in the late 1970s so that, at some later date, they could
step it up to a true HDTV system by increasing the number of picture lines
without too much difficulty. In 1986 the European Broadcasting Union adopted
MAC as the standard for all direct broadcasting by satellite in Europe.
France’s satellite TDF-1 is now using MAC for test transmissions.

Two features distinguish MAC from existing systems: its sound is digital,
not analogue; and it separates the colour (chroma) and black-and-white (luma)
picture signals in time, not in frequency. The MAC system transmits luma
and chroma in alternate bursts, rather than in different frequency bands,
as PAL and NTSC do. This prevents the anomalous effects, such as moire colour
on check jackets, that occur when a PAL or NTSC receiver mistakes fine detail
information for colour information.

The Eureka system, known as HD-MAC, will double the number of picture
lines from 625 to 1250. It will also make the picture wider, increasing
the aspect ratio from 4:3 to 16:9. The signal bandwidth will be around 25
megahertz, which is of course too wide even for a satellite channel. Consequently,
engineers will compress the signal so that they can broadcast on a 12-megahertz
satellite channel. A computer will transform the 1250-line picture leaving
the HDTV camera in the studio into digital code. It will map the picture,
logging the parts that are changing. The digitised signal will then be converted
into two parts: a conventional analogue image of 625 lines, which any MAC
TV set can receive; and an extra, or control, digital signal that contains
information about the picture content.

This control signal will be transmitted in much the same way as conventional
teletext, that is, in the unused picture lines that form a thin black border
at the top and bottom of the screen. An HD-MAC receiver will use the control
signal to process the accompanying analogue signal. The technique, called
Digitally Assisted TV, or DATV, was originally developed by the BBC.

Around 1 million bits a second of DATV data will tell an HD-MAC receiver
what parts of the picture are stationary, and what parts contain motion.
The receiver will respond by combining the detail of stationary areas from
two full pictures while leaving untouched the moving parts. It will also
double the number of lines to 1250. The effect on screen will be clearer,
sharper pictures, helped by the fact that the human eye cannot detect as
much detail on moving objects as it can on stationary ones. Receivers will
display the images on wide screens with an aspect ratio of 16:9.

Conventional MAC sets will simply ignore the control signal and display
ordinary MAC pictures with an aspect ratio of 4:3, which means some of the
side action will be missing. Because the main MAC signal will transmit images
of 625 lines, even existing PAL TV sets will be able to display the pictures
when they are connected to a MAC decoder box.

These neat and orderly plans for the future of television in Europe
are in jeopardy, however, following disagreements between Britain and the
rest of the Continent over the number of digital sound and data channels
needed for the MAC system. Transmitting more channels will create a better
product, but there is then less chance of the old cable networks, which
serve most continental cities, being able to distribute the signal. Britain,
with only a small cable network, is firmly committed to one variant called
D-MAC, which has eight channels. This will allow multilingual broadcasting
in stereo, which will be particularly useful after the inauguration of Europe’s
single market in 1992. France and West Germany, on the other hand, are equally
committed to another, incompatible, variant called D2-MAC, which has four
channels.

The disagreement has delayed the development of MAC satellite receivers,
and prompted Sky Channel to choose old-fashioned PAL for its broadcasts,
which began in February from Luxembourg’s Astra satellite. This means that
MAC is no longer the real high street standard for satellite TV, at least
in Britain.

Despite the confusion over the broadcasting standards, PAL and MAC,
Europe is committed to a format that displays pictures made up of 625 lines
interlacing 50 times a second. This has forced Japan to give up hope of
selling Europe its Hi-Vision system, which displays pictures made up of
1125 lines interlacing 60 times a second. The Japanese are, however, still
trying to convince recording studios to buy Hi-Vision systems to replace
film equipment.

A technical problem peculiar to Europe makes this highly undesirable
for broadcasters and viewers. It is difficult to convert from one format
to another; from 1125 lines to 625 lines and from 60 fields a second to
50 fields a second, or to film for projection at 24 pictures a second in
cinemas, where there is still no video projector that can match the performance
and price of film projectors. Engineers must simply throw away some of the
picture information, but even then conversion causes blur and judder on
moving objects; particularly disturbing is facial detail in close-ups, which
comes and goes. This may not be noticeable on a small TV set, but it is
obvious on large TV and cinema screens. The effect can be even worse than
the distortion caused when TV broadcasters transmit, after conversion, programmes
designed for the 525-line format of North America to European or Australian
homes where TV sets display 625-line pictures.

There is only one hope now of achieving a world standard: if engineers
record pictures from studio cameras on video tape as digital code, chosen
with compatibility in mind, they can convert the coded signal into any analogue
format – high-definition, or current 625-line or 525-line – without losing
quality. But recording pictures as well as sound in digital code requires
enormous processing power. Conventional TV pictures of 625 and 525 lines
produce digital data at a rate of more than 200 megabits a second, which
is around 100 times the speed of the digital audio signals from domestic
compact discs. Converting wide screen pictures of more than 1000 lines into
digital code produces a data stream of more than 2000 megabits a second.
Engineers can reduce the volume of data by coding only the changing and
moving parts of a picture but this still leaves a data stream of around
1000 megabits a second.

Several Japanese companies, including Sony, have made experimental recorders
that can work at 1000 megabits a second, but there is a world of difference
between building a prototype in the laboratory and producing recorders that
will work reliably in real studios. Electronics companies are a long way
from achieving their aim of replacing 35-millimetre film with high-definition
video.

Film reacts to the challenge

Kodak is capitalising on the video muddle. It has introduced a family
of ‘extended range’ films for the cinema that will let directors record
shots in daylight, without needing to use filters for colour correction,
which has been the standard practice in the motion picture industry. The
new films are also ‘faster’: they can capture clear images in poor light.
Kodak is now demonstrating the new range to the film industry in Europe.
‘There will be more than one high-definition TV display format around the
world,’ says John Croft, technical manager of Kodak’s motion picture and
audiovisual products division. ‘It seems certain that 35-millimetre film
will be the common medium. Our objective was to make film the best choice
for originating high-definition television.’

The silver halide emulsion of Kodak’s extended range film has a tabular,
or T-grain, structure, which captures more detail than the cube-shaped crystals
used before. T-grain crystals create a larger surface area of light sensitive
silver, so the emulsion is more efficient at collecting light.

Kodak describes its latest development as ‘a new beginning’ in its battle
with magnetic tape over the future of HDTV. But its competitors are not
so sure. One of the very few things that the disparate electronics industry
can agree on is that film technology is nearing ‘The End’. The unresolved
question is, when?