London — A world television news service is under discussion here. In about four years , it could pop up on American as well as European screens, written and produced in London.
''We're looking at it,'' confirmed the managing director of British Broadcasting Corporation television, Aubrey Singer, in a wide-ranging interview that also covered other challenges facing the BBC in the years ahead.
No hard and fast decisions have yet been made, but the idea is to use the second of two channels assigned to the BBC on a brand new British communications satellite to be launched by the European Space Agency in the winter of 1985-86.
A two-hour program would be put together in London from 11:00 p.m. to 1:00 a.m. British time. Since Britain is five hours ahead of the East Coast of the United States, that could catch large early evening audiences on both East and West coasts.
The program would be part of overall BBC plans for the second satellite channel, under the general title of ''Window on the World.'' The channel would also show the best of European culture, including BBC repeats.
Mr. Singer is not unduly worried at possible opposition to a news program from the US networks. He sees US cable companies as a potential market. It is also possible, he thinks, that the networks might subscribe to the new service, which would become a kind of wire service of television.
Not only the US but also other countries could buy the service and use as much or as little of it as they wished.
The idea is one facet of a challenging new period ahead for BBC television as a whole. As in the US, so in Britain, television is bracing for a revolution that is much nearer than many people believe.
The US already has cable and a wide variety of channels. Britain, with just three channels at the moment, and hardly any morning or late-night programming, is just approaching these developments - but with one big difference.
The British tradition is for television to be a public service, accountable to Parliament although free from editorial control, and financed through a viewer license fee.
This has helped make the BBC one of the most famous broadcasting services in the world.
Its reputation for independence was enhanced during the Falklands crisis, when Prime Minister Margaret Thatcher sharply criticized the BBC for too much coverage of Argentine opinion and too little flag-waving patriotism. The BBC stood firm against all pressures and criticized the government for inept handling of TV requirements.
The question now: whether that reputation for independence and excellence can survive the onset of more channels, British breakfast television, satellite broadcasting, and an extraordinarily high penetration of video cassette players and tapes into Britain.
A world TV service, something like the World Service on BBC shortwave radio, might be one way to preserve the BBC image abroad.
The ebullient Mr. Singer, who took over as managing director, television, in April of this year, sees the BBC as the ''center'' of British TV, the heartland of excellence, which sets standards for its competitors.
''The BBC must keep its credibility and its image,'' he said in his office high in the massive BBC television center at White City in London.
''Preserving the BBC as the heartland is at the root of my problem in the face of all the changes ahead in the next five years. . . .''
Among other points, he sounded a note of caution about the wisdom of Britain following the US example of cable television.
''We worry about cable, of course,'' he said. ''If cable bids high for sport and other programs, it could deprive our BBC viewers of those programs. In the US, cable has siphoned off about 10 percent of your viewing audience, and that siphoning effect could happen here.
''But there is a great danger in this country as we look to the US. We might pin too much hope to late 1970s and early 1980s US cable technology when we go ahead in the late 1980s.
''I would not be surprised if the US cable TV boom turns into a quite a bust. Too many channels, too many franchise promises made and not fulfilled.''
Already 2.6 million British households receive the three existing channels here (two BBC and one commercial) by cable, mainly in areas where conventional reception is poor. Another 2 million could be connected without difficulty, but it could cost as much as (STR)2.5 billion ($4.2 billion) to wire the whole country.
A three-man government committee under Lord Hunt was set up in March of this year to advise on regulation and prospects. It reports at the end of September.
Among the other challenges to the ''heartland'' BBC TV:
* Channel 4.
It will begin Nov. 2 of this year. Already a ''4'' test pattern card can be seen when button four is pressed on home TV sets in many parts of the country.
Under its director, Jeremy Isaacs, it aims for 10 million viewers in its first year with about 60 hours of programs a week. It will be a commercial station, licensed by the Independent Broadcasting Authority, except in Wales. Programs are being provided by regional commercial companies and by independent producers.
''I can't see him [Isaacs] - apart from the first few weeks of curiosity value - getting much more than 3 to 6 percent in the first year,'' Mr. Singer said. ''He will have to take viewers away from the three existing channels.''
Channel 4 is said to be aiming particularly for the better-educated viewers of BBC-2, which has risen from 8 to 12 percent of the total audience in the past year.
Mr. Singer hopes, however, that his rival will succeed. ''If he doesn't attract enough advertising revenue,'' he said,''he will start to compete hard, and if we reply in kind, you could get vicious competition on the model of the US networks.''
* Breakfast television.
The BBC plans to jump in with a 6:30 a.m.-to-9:00 a.m. service in January, perhaps as early as Jan. 3.
The idea is to start before its rival, TV-AM, a commercial company headed by former British Ambassador to Washington Peter Jay, begins in February.
''We never really wanted to get into it,'' Mr. Singer admits candidly, ''but we are in it now and we will do it con brio.''
The BBC will have to pay for it out of its existing budget of about (STR)535 million a year ($909 million), and will have to fill 300 new posts. Asked how it would be done, Mr. Singer waved a hand. ''Operating economies,'' he replied.
A plan to combine popular BBC radio breakfast programs with TV has apparently failed. Mr. Singer sees an audience for breakfast TV, but one that will grow slowly.
He expects to have 1 million viewers in the first 12 months, and estimated his commercial rival will have about another 1 million. The BBC has studied US morning programs, though Mr. Singer politely declines to comment on them.
One problem for Britain: Breakfast TV is usually watched on a second set in the kitchen or bedroom, but only 20 percent of British households have more than one set today.
* Television from space.
The first channel on the British satellite will be pay-TV - first-run movies like Home Box Office in the US. The second, Window on the World, is supposed to be free, but in fact the signal decoder on top of the set will have to be rented.
* Video cassettes.
The British habit of renting TV sets and video players by the month means that about 44 percent of households will have a video player by 1985. Only Japan and Sweden approach this figure.For the BBC this means, in part, trying to market its own cassettes - which in turn means solving union problems before dramatic plays and classical music can be used.
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