Edith Piaf, France's version of Billie Holiday or perhaps Judy Garland, was the daughter of a street singer and a circus performer who was brought up in a brothel, discovered by an impresario singing in the street and became one of the most loved of Europe's stars.

She was less than five foot tall - hence her nickname, Little Sparrow - and had affairs with a clutch of notables, including Yves Montand and Marcel Cerdan, the middleweight world boxing champion. She drank gallons, injected morphine - up to 10 times a day - contracted crippling arthritis and died before she was 50, in 1963. She regretted nothing, as her famous song suggests. What a film her life ought to make.

Unfortunately, Olivier Dahan's "emotional journey" through this triumphant but tragic existence leaves us none the wiser about many of the details we'd like to know, or knowing, would like to see on the screen.

What about her marriage? Or the child she had and neglected, just as she was virtually abandoned in her youth? What about her "good war" in Paris under the Nazis? And what about the stream of men who came knocking at her door, generally successfully?

The questions proliferate throughout a long film distinguished not so much by Dahan's dizzying skill at flitting from one period of Piaf 's life to another but by a fabulous performance from Marion Cottilard. She mimes along to the genuine Piaf soundtrack with all the fervour of the singer herself, allowing one to forgive the film's omissions and its overall quality as a fairly ordinary French period piece.

Cottilard, who is probably best recalled here as the girl in the Taxi series (galumphing farces not requiring any great acting zeal), transports us somewhere very near Piaf 's strange, self-destructive soul, whether as an old and raddled invalid or as a young and chirpy songstress.

Not even the dull patches in the film - and there are some when one yearns for an editor to take up the scissors and cut to the chase - can make Cottilard's Piaf seem ordinary.

Around her wheel Gérard Depardieu as Louis Laplee, the man who discovered her, Sylvie Testud as her best friend, Momone, Emmanuelle Seigner as her substitute mother in the brothel, Jean-Pierre Martins as Cerdan, Pascal Greggory as Louis Barrier, her intrepid manager, and many other faces familiar from French cinema.

None of Dahan's formidable cast lets him down. What prevents the film from taking flight is both the constant movement between periods of Piaf 's life and anything more than perfunctory explanations about her art itself.

Perhaps the essence of that art was that it brought the music of the working-class streets into the homes of the middle classes who thought themselves so much more sophisticated than Piaf herself. And that is only briefly sketched in the film, in the tiny scene when Piaf meets Marlene Dietrich, who praises her as if she were a successful little urchin before walking away with the hauteur of a real icon.

But, of course, Piaf was and remains an icon herself, and Cottilard tells us just why.