The liabilities of filming staged opera are considerable. But making movies of opera from scratch has yet to be much more satisfactory. Joseph Losey's ''Don Giovanni'' is but one sample of a movie that does not work as an operatic or cinematic totality, no matter how many splendid moments there may have been peppered throughout. The recent airing of ''Willie Stark'' on PBS showed that a satisfactory compromise can be reached when an operatic production is taped without an audience, as if in a studio: Camera angles are more flexible, and the general results, in the case of ''Stark,'' were as impressive as filmed opera has yet seen.
Jean-Pierre Ponnelle, a sometimes too gimmicky director who is in vogue now, has been fascinated by the potentials of cinematic opera. Not many of his films have been very good - either too primitive in execution or too eccentric in ''interpretation.'' His latest project is Mozart's ''La Clemenza di Tito,'' (PBS , Monday, Oct. 19, 8-10:30 p.m., check local listings for premiere and repeats), to be aired in stereo simulcast as part of the Great Performances series.
James Levine conducts the Vienna Philharmonic. He treats Mozart's last opera - written in the difficult opera seria form, full of long arias and static ensembles - as if it were the great masterpiece of the operatic literature. He suffuses it with what he feels are revelatory dollops of life, passion, tenderness, volatility, emotion, and makes it all come throbbingly to life - which is what any great conductor should do to an important score.
The cast features Eric Tappy as Tito, Carol Neblett as Vitellia, Catherine Malfitano as Servilia, Anne Howells as Annio, Kurt Rydl as Publio. They are all very fine in their roles (though Miss Neblett has some very odd ideas about phrasing, about vocal color, and general pronunciation). Tatiana Troyanos's Sesto was in a different category - a totally committed, superbly vocalized performance that elevates this venture into something extraordinary.
Unfortunately, Ponnelle's contributions range from the bizzare to the inexplicable, inspiring laughs where tension should reign. Shot on location in the ruins of Rome, the production has no real sense of period or locale: We follow the story of Romans, filmed against the rubble of that civilization, with the principals dressed in elaborate 18th-century gowns and costumes. The gestures are of an early-Hollywood broadness. Rage is communicated by popped or crossed eyes. Vitellia and Servilia run around in ''Bride of Frankenstein'' fright wigs. Titus is played as if utterly insane.
Some of this high stylization may have worked on the Salzburg stage in the right visual context, and in an attempt to ''sell'' this basically static work as living drama. But Ponnelle puts forth no consistent context - ruins aside. Most of the time, his motions fight rather than help the music.
Thus, musically this is a distinguished, often memorable ''Tito,'' while visually it tends to the ludicrous.