AFTER just six months on-air in Singapore, MTV Asia, a part of STAR TV's six-channel package of programmes broadcast out of Hongkong, has cut off its feed to the state-run broadcaster, the Singapore Broadcasting Company (SBC). While both sides were reluctant to discuss the matter, a STAR TV spokesman said that MTV had withdrawn re-broadcasting rights from SBC ''due to infringement of the MTV Music Television trademark and other STAR TV rights''. SBC is understood to be keenly trying to renegotiate the deal. Whatever the rights or wrongs of the argument, one thing is clear: MTV Music Television is having as much of an impact on the Asian television and music markets as it did in the United States almost a dozen years ago and in Europe 51/2 years ago. After just 18 months of transmissions, it would seem that the MTV logo is almost as powerful a marketing weapon in Asia as it is in the United States or Europe. ''The pan-Asian music business has grown up by a huge percentage since the advent of MTV,'' said a long-time Asian music industry operative, who now heads a regional concert promotions group in Hongkong. MTV Asia is a joint venture between STAR TV and US firm Viacom Networks. Under the contract, STAR TV pays a basic licence fee, with a revenue share going to Viacom once the channel passes a certain profit threshold. ''That suits us perfectly,'' said Mr Arnie Tucker, a senior vice-president with STAR TV. ''Essentially, Viacom supplies the concept to us for a low cost and we get to take the risks.'' STAR TV is notorious for a tough bargaining stance and has cut ''low cost'' agreements with the programme suppliers for each of its current channels. But the MTV Asia operation is reckoned to be the most expensive as far as STAR TV is concerned. Since STAR TV puts most of its local production resources into packaging the programming and covering not only the marketing but also all the transmission costs, MTV Asia's costs are inevitably higher. But whether advertising revenues and market penetration are what might have been hoped for when the service was launched is another matter. General manager Mr Don Atyeo, formerly chief executive at the Power Station, the now defunct British-based music channel, claimed that MTV Asia was ''well on target'' within its five-year business plan. ''In fact, we are doing far better than expected. Things are picking up so fast that in January this year the sale of advertising exceeded the entire sum for 1992,'' he said. But that is a statement made about all the STAR TV channels. All of them are far from being profitable at this time and some analysts say they will never be profitable. Nobody else in the world has made a profit from a stand-alone, advertising-driven channel. Much of the advertising that MTV Asia screens is believed to be discounted at best, according to advertising industry watchers. ''I suspect quite a lot of the current advertising is barter and is a part of initial deals when the station was launched,'' said Ms Maggie Burden, the media director for Leo Burnett Asia. ''And I think MTV Asia could well not be getting the penetration the MTV network gets elsewhere.'' Even so, said Ms Burden, MTV Asia provided a ''very targeted niche audience'' suitable for the likes of Reebok, Coke and Levis. Mr Mark Ingall, Bozell's executive media director for Asia Pacific, was surprised that MTV Asia was not the most consistently successful channel in the STAR TV stable from the outset. ''You would have expected them to be the most popular from the start because they have such an identifiable audience. But it has taken time for them to pick up speed.'' A recently released STAR-TV-commissioned diary survey conducted late last year shows that in Taipei, Hongkong, Bombay and Delhi, more than 6.6 million viewers aged nine and over watched the station at one time or another over a four-week period. But according to the figures, the average MTV Asia viewer in the four surveyed cities will watch for an average of between two and 21/2 hours per week: that is, half an hour a day, at best. When it is considered that MTV Europe was losing between GBP2 and GBP5 million (about HK$24 to $60 million) per annum three years after launch, MTV Asia must be a long way from overcoming a substantial deficit. Mr Atyeo said the station had begun to test the concept of pan-Asian music only last year. ''We wanted to see if the station, like all the STAR TV channels, would sell across borders,'' he said. ''Now, after a year, we know our market and know that while the pan-Asian service works in a number of out territories, there are very specific tastes. ''We soon concluded that if we wanted to reach audiences locked on local stars we would have to become part of the culture,'' he said. ''MTV has never done this before. In every other region it has been a global approach. We can't afford that.''