The world moved a tiny bit closer to a new era of home TV Thursday.

From a studio in Ottawa, signals from a revolutionary system known as high definition television were bounced by satellite to a darkened hearing room in the Rayburn building on Capitol Hill, conveying in disarmingly sharp, wide-screen images and in digital sound the greetings of Canadian officials and clips from a miniseries being produced there in the new medium.

It was the first international broadcast by satellite of HDTV, Public Broadcasting Service Senior Vice President Richard R. Green announced with some pride to legislators, reporters and curious hall wanderers who had stopped in for a peek. PBS sponsored the demonstration with the Canadian Broadcasting Corp.

HDTV is to today's TV what the compact disc is to the phonograph record, an advance so startling that few people exposed to it are likely ever to feel fully satisfied with the set in the family room again. It holds the potential to shake home viewing habits and equipment with every bit as much force as the advent of color almost three decades ago. It is already starting to revolutionize studio production techniques and could eventually challenge 35mm film.

Almost everyone in the television industry today expects HDTV will take hold in this country in a big way, but no one can say when and in what form. Members of the U.S. industry are tussling with each other over broadcast band allocations and a common technical standard. Researchers are devising competing and incompatible systems at labs around the country. With no one sure what system will be adopted, companies in general are nowhere near ready to begin production.

The Japanese, in contrast, have made their decisions. They alone have settled on technical specifications of a national broadcasting system. They alone have electronics companies that are making and selling a full line of production equipment, as well as gearing up to make home sets. They alone have an official timetable for when their country's ordinary citizens will be able to see HDTV in their homes -- late 1990 or early 1991, via a satellite.

HDTV could evolve into a $100 billion industry by the end of the century, many analysts believe. Many American specialists now are wondering how this country has dropped so far behind and whether Japanese world dominance in yet another new and enormous field of technology is already a foregone conclusion. Slowly, ideas are shaping up for how the United States can catch up, but the Japanese lead is big.

Today's television is based on a set of technical standards that has proven remarkably durable. First adopted in 1941, it has taken television from tiny round-screen black-and-white sets through to big-screen color and most recently, stereo sound. But now, many experts feel that the old standards must be abandoned.

TV pictures are composed of tiny horizontal lines, made up of even tinier dots. The lines are stacked one atop the other on the screen. Under electronic command from the broadcast signal, the lines wiggle, expand and contract and shift from color to color at lightening speed. The eye, viewing them from a few feet away, merges them into a single unit. Today's TV system has 525 of the lines. Japanese HDTV more than doubles that to 1,125 and thereby achieves a much higher degree of clarity and detail. It renders colors with far greater fidelity, too.

Industry psychologists also decided that most viewers would prefer a wide screen. The current boxy one has been elongated by the Japanese to proportions roughly those of a movie screen. Sound has also been upgraded, through stereo digital technology, which underlies the crispness of the compact disc.

For viewers, it is usually love at first sight. "They take one look at that machine and they say, 'When can I have that in my home?' " said Mark Blandford, executive producer of "Chasing Rainbows," a 14-hour miniseries being shot by the Canadian Broadcasting Corp. in HDTV.

HDTV opens up myriad new possibilities: end-zone to end-zone football, wide screen 35mm film movies on TV without the annoyance of chopped-off edges, wrap-around digital sound. Equally important is that the picture can be big without degradation. Any long-distance air traveler knows how dissatisfying projection of conventional TV is. But HDTV enlarges with such clarity that wall screens in family rooms might one day be common, along with HDTV systems instead of 35mm film projectors in small theaters.

HDTV tape could eventually replace 35mm film as a production medium, too. Already a few pioneering studios are working in it. Rebo High Definition Studio in New York, for instance, since last November has turned out commercials and rock videos; it is working on a feature length film. HDTV has the advantage of being viewable (eventually) on its own, or transferable with comparable quality to film or conventional video tape. It gives more flexibility in special effects, too. "We were the first in this revolutionary process in the States, but we certainly won't be the last," says studio partner Denis Bieber.

Japanese companies look far into the future, especially when dominance in a new generation of high-volume consumer products is at stake, and often cooperate more than do their U.S. counterparts. The Japanese electronics and TV industries have been laboring on HDTV in earnest since 1970, under the coordination of NHK, the semiofficial national TV network. By some estimates, they have sunk $300 million into research since then. Today, the payoff seems well within sight.

Hitachi, Matsushita, Sony, Toshiba, Sanyo and others among the electronics giants of Japan have laid firm plans to begin turning out consumer sets. A smaller number of companies are already selling HDTV studio equipment. Sony, for instance, has already sold more than 100 studio-quality HDTV recorders and somewhat fewer professional cameras.

NHK is stocking up on HDTV programming, which now is converted to conventional specifications and broadcast over the regular network. Since December last year, it has been conducting experimental broadcasting by satellite in the early morning and preparing for the big leap into commercialization that is scheduled to come with the launching in 1990 of a new satellite.

Japan has no plans now to broadcast HDTV through TV stations on the ground. Rather, the satellite signals will beam down across the archipelago, directly accessible to any Japanese household that has a small receiving dish, a "decoder" to process the signal and a high definition TV set. "It will be very expensive," said a Sony official in Japan -- around $3,500 is the expectation initially for all three components. "Application at first will be limited."

Regular TV sets in Japan will not be able to pick up the new signals unless a costly converter is attached. But high definition sets will be built to pick up both high definition and conventional pictures. The Japanese throw out appliances almost at the first sign of wear or obsolescence. The idea in making the new sets compatible with old signals is to further speed a mass switch-over by bringing HDTV prices down within a few years to the cost of normal TV sets. "Satellite reception will be very popular within 10 years," predicts Yozo Ono, an NHK engineer based in New York.

Eventually, he says, all nationwide broadcasting in Japan is intended to be by satellite and in high definition, with TV stations on the ground concentrating on localized programming in conventional signals. No one knows if the Japanese will pull off such an enormous transformation, but they will try very hard.

There is no substantial technical reason why Home Box Office and other services that use satellites to distribute programming could not use the Japanese broadcast system, known by the acronym MUSE, in the United States, with Americans buying Japanese dishes and receivers. Indeed, many people in the television industry believe that HBO is planning to do something like that around 1991. The company acknowledges intense interest in HDTV but denies it has any definite plans for introduction.

Gritting their teeth right now are the three networks and ground broadcasters in general, represented by the National Association of Broadcasters and the Association of Maximum Service Telecasters.

The grim fact for them is that the world's only functional HDTV broadcast system, dazzling everyone who sees it, is open to their satellite competitors but not to them as their stations on the ground now function. MUSE also presents technical problems for cable operators.

The problem is space on the broadcast band. Conventional TV channels cover about 6 kHz on it. However, the MUSE signal is so packed with electronic data that it won't fit into that space -- it needs about a channel and a half, either on the open air or cable. There is plenty of space in the frequencies that satellites use. That's not the case for ground TV stations as currently allocated by the Federal Communications Commission. Broadcasters have begun a bureaucratic campaign to reserve for themselves those extra half channels they may need to go into HDTV.

This spring they demanded that the FCC reject a proposal that police and ambulance communications and other mobile radios be assigned unused space now reserved for TV. Without that band space, said NAB president Edward O. Fritts, "we are afraid, fearful, concerned that we will be left with a system that would be less than competitive." NAB officials talk somberly of the demise of locally controlled broadcasting in the United States. The FCC has yet to rule on their request but has pronounced itself in favor of leaving HDTV options open.

At the same time, American researchers are working hard to develop an HDTV broadcast system that would address the concerns of ground stations and cable operators. One approach is to compress the signal into one channel. NBC last week announced a system that it says fits this bill without the degradation in picture quality that attempts at a squeeze normally cause.

Other systems, notably separate ones developed by North American Philips and Dr. William Glenn of the New York Institute of Technology, are intended for broadcast on two channels simultaneously.

The FCC and the industry in general are anxious not to antiquate the estimated 140 million conventional sets in use in the United States. This was avoided successfully with the color revolution in the early 1960s -- color sets received color, but old sets got a perfectly good black and white picture, a fact about which the industry is still congratulating itself.

A big draw in NBC's single-channel system is that it would be receivable by present sets, though they would not produce a high definition picture. The two-channel systems are designed to be compatible, too -- old sets would tune in to just one channel and be blind to the second. HDTV sets, however, would receive both and use electronic information from the second to upgrade to HDTV quality the basic picture received on the first.

Further complicating things, companies in Western Europe are at work on systems that would generally be incompatible with the Japanese system and with ones under development here. Many people here see the Europeans' direction as more politically than technically motivated. It is called an attempt to reserve the market there for European manufacturers, rather than accepting the Japanese systems and opening the doors to their products.

Europe maintains a healthy consumer electronics industry and wants to keep it that way. U.S. companies, in contrast, have virtually withdrawn from the television and audio industry. Today, Zenith is the only U.S.-owned company still making TVs and there are no U.S. makers of VCRs. The Japanese are making vast inroads in broadcast equipment, too.

The U.S. industry tends to blame low profits and unfair competition from the Japanese and other Asian countries like South Korea and Taiwan. Its critics point more to alleged faults in the industry itself, including poor planning, high wages and a lack of modern plant and strategic foresight.

Critics see it all happening again with HDTV. The Japanese have a working system and their factories are making the equipment; the Americans are still doing basic research, arguing over standards and are nowhere near producing hardware on any significant scale.

"We're talking about immense markets with billions of dollars in manufacturing and potentially tens of thousands of jobs," says Rep. Don Ritter (R-Pa.), a member of the House subcommittee that sponsored the hearings on Thursday at which the HDTV demonstration took place. "We are talking about the next revolution in television and right now we are just not a player."

There is talk now that HDTV could provide a window for the U.S. industry. In testimony to the subcommittee last week, Association of Maximum Service Telecasters Chairman Fred Paxton suggested that a Japanese-style consortium, perhaps with federal antitrust exemption, might be in order to help the U.S. industry catch up. The American Electronics Association is also depicting this as a big chance to its members.

Because of the cost of equipment, some analysts suggest that MUSE direct satellite broadcasts will be slow in catching on here. This would give U.S. companies breathing space for developing a system usable on open-air broadcast and cable.

To that end, members of the industry and the U.S. Commerce Department are pushing the FCC to approve a U.S. broadcast standard by 1991 so there would be no confusion as to what type of equipment to make. Some U.S. companies, meantime, are already producing peripheral studio equipment to go with Japanese production systems. The National Association of Broadcasters has formed a technical center for HDTV research.

Still, many analysts say there is no evidence the U.S. industry has begun gearing up for the enormous effort it would take to get back into the consumer business with HDTV. Researchers last week complained to the House committee that U.S. companies were not willing to put up the money required to become a serious force.

"We recognize that there's a window of opportunity that may be closing extremely rapidly," says J. Richard Iverson, president of the American Electronics Association. But he suggests that even if U.S. companies don't produce finished sets, there could be big business for them in producing the electronic components they require.

Other analysts just take it for granted that the Japanese will dominate this market, perhaps with the Europeans playing a role too. In Thursday's demonstration, the pieces of equipment in the hearing room bore the names Sony, Hitachi and Panasonic. In a demonstration early this year in which the Washington CBS affiliate WUSA broadcast an HDTV signal on two UHF channels, recalls Fritts of NAB, the only American equipment in sight was the antenna.

Not everyone is convinced, however, that the first American HDTV will originate outside the home. Some see it arriving initially through special VCRs and laser disc players that would use special movies that would appear on the shelves of neighborhood rental shops.

A few people also are wondering about the social costs of the new technology. Will HDTV make America even more of a glued-to-the-tube society? Rep. Ritter asks whether children would be able to develop strong reading and writing skills with such a powerful distraction in the next room.

He worries about himself too: "As a late-night TV viewer, I find it's going to be even harder to turn off the tube.