THOSE WHO WORRY about the future of opera look to film the way Great Britain viewed the United States during World War I--as a sleeping giant whose enlistment would surely break the stalemate. Harried impresarios hope filmed opera's wider audience will keep money flowing down the gaping drains of the world's international opera houses over the next decades, and end their financial stagnation. The more starry-eyed even suggest film will "restore opera to the masses" in the days of $50 tickets to the Metropolitan Opera.

But until very recently, simple technical problems stood in the way of decent opera films. Movie theater sound systems couldn't deliver the dynamic range of operatic performances without unbearable distortion; directors didn't know how to dub singing voices convincingly; the acting of singers showed embarassing flaws under the close scrutiny of the movie camera. Joseph Losey's Don Giovanni is remarkable not because it records a worthy performance--it's rifled with musical problems of evert sort--but because it solves the worst of the artistic problems that have kept opera off the screen. With any luck future directors will be able to use Losey's film as a manual for capturing better performances and interpretations.

Ingmar Bergman's Magic Flute, always cited as the best-realized opera film prior to Don Giovanni, neatly sidestepped all the conceptual problems of the hybrid genre--it pretended to be a filmed record of a performance in a provincial opera house, with shots of the audience thrown in to be sure you understood the universality of Mozart's message. Losey never wavers from his no-holds-barred outdoors staging, using the Palladio villas near Vicenza as an occasional refuge from the bright sun that over-exposes many of the scenes.

Losey's breakthrough is the meticulous attention he gives to sonic perspective. Many made-for-TV opera films ludicrously maintain the same concert-hall acoustic whether the singer is standing in a bedchamber or a wheatfield. In Don Giovanni, when the camera zooms in on a singer's mouth, the voice becomes more distinct and louder--and you can tell simply by listening whether a singer is indoors or out. Losey's dubbing technique, too, seems more precise and less distracting than most, including Bergman's. Only one singer, Malcolm King as Masetto, suffers from the "disconnected mouth" disease endemic to filmed singers.

The prospect of juggling the schedules of international opera stars, a conductor, and a symphony orchestra on top of the usual scheduling troubles of any film have generally daunted directors; Losey has shown that it can be done. It now remains for someone to do it, better--because this is not a Don Giovanni anyone would be happy with as a standard or even acceptable version.

Despite the musical ambition implicit in the international cast and the Paris Opera name (Bergman used an all-Swedish cast for his Magic Flute), this Don Giovanni is musically undistinguished. Lorin Maazel's conducting sounds muddy and sluggish throughout--which could easily be the fault of the Exeter Street's Rocky Horror-blasted sound system. None of the singers does very much of the ornamentation most music scholars today believe was a critical part of performances in the composer's time. Most of all, there's a surprisingly lackadaisical air about Mozart's music as Losey presents it--as though the added visual verisimilitude could take some of the burden off the music and let the singers take it easy for a change.

Ruggero Raimondi's Don is a middle-aged, thin-lipped, white-faced sadist, a man more easily pictured flogging cats than seducing women. Raimondi fits in well with Losey's class-conscious interpretation of Da Ponte's text--he sees Don Giovanni as the consummate self-indulgent aristocrat. There's nothing wrong with coloring the opera this way, but Raimondi and Losey paint over and obliterate the other half of Don Giovanni's character, the youthful embodiment of unbounded energy who mesmerized the romantics. They do Mozart and Da Ponte an injustice by simplifying the libretto's psychological tangle to a black-and-white social dialetic. Figaro would have better served such an intent.

The other roles run from the accomplished but not overdone leporello of Jose van Dam to Kenneth Riegel's wooden Don Ottavio. Among the women, Kiri Te Knawa's Donna Elvira stands out as the most musically agile and dramatically subtle. Edda Moser afflicts Donna Anna with an unfocused voice and the worst of operatic mannerisms--especially ludicrous with instant translation in English subtitles. She shrieks and sways--the subtitle reads, "I'm fainting." She shrieks once again and staggers to embrace a marble column--"I'm dying."

Those subtitles give this Don Giovanni a great advantage over live opera, but pose a danger as well. By offering an instant, easily consulted libretto, they restore to the recitative sections the cynical bite normally lost on English-speaking audiences. Future directors. though, would do well to find themselves better translators than Losey's. As the spirits of hell clamor for the Don's soul, for example, he shouts, "They agitate my viscera!"

THE SPECIFIC FLAWS of this Don Giovanni will certainly prevent it from bringing opera to a mass audience, and--despite all that film offers opera listeners, financially and technically--it's doubtful the opera movie will ever go over big. Audiences today have trouble sitting through the two-and-a-half hour extravagant spectacle of Apocalypse Now; Losey's three hours of set pieces won't fare any better.

The people who will go see Losey's film are the same people who buy seats for the Metropolitan Opera when it visits Boston each spring, not the great unwashed "masses" who couldn't care less about opera, who would rather see the latest Airport movie than Don Giovanni--or, better yet, go home and turn on the television. To "Mork and Mindy," too, not PBS.