Is Eminem a movie star? Only when he raps.

Playing Jimmy "Rabbit" Smith Jr., a white hip-hopper at odds with everything in his off-kilter trailer-park family and crumbling Detroit environment, he's supposed to ooze bruised sensitivity like a latter-day James Dean. Instead, Eminem holds the screen with hammer-and-tongs determination. He's a galaxy away from the glinting emotionalism of a man born for the camera.

Eminem channels his energy into expressing a single feeling at a time as he berates his beautiful mother Stephanie (Kim Basinger) for sleeping with a jerk who's roughly his own age. Or begs for an extra shift at his metal-stamping job. Or moans a lullaby to his cute-as-a-smudged-button kid sister Lily (Chloe Greenfield). Or jousts off-stage - physically and verbally - with his biggest on-stage rivals.

It's a minor feat for an untrained actor to convey Oedipal rage, working-class desperation, fraternal gentleness and competitive fury as well as Eminem does here. But unless you're invested in seeing a pop idol keep from embarrassing himself, his single-minded intensity becomes boring.

Eminem emanates the galvanic electricity that's made him the focus of adulation and excoriation only in the 15-minute grand finale. It's a rap battle royale that recaps the rest of the movie in gutter rhyme.

The rest of the movie makes you pay for your enjoyment.

No director over the last decade has demonstrated greater growth leaps or delivered more various and deeper pleasures than Curtis Hanson (L.A. Confidential, Wonder Boys). At least he gives 8 Mile a hardscrabble visual integrity. He calmly navigates the audience through a week in the life of Rabbit - an old-fashioned day-in-the-life-story times seven. He makes a sooty soap opera real by anchoring it in scorched-earth locations filled with shuttered stores, gutted buildings and houses begging to be razed.

Tick off the incidents the movie contains and it sounds like a cross between a cliffhanger and a tearjerker.

The movie starts with Rabbit panicking at one rap battle and running off the stage and ends with him triumphing at another. In between, he splits up with a gal who says she's pregnant (Taryn Manning), moves into his mom's trailer just when she receives an eviction notice, and has a fling with a forward young woman (Brittany Murphy) who functions as a floozy muse.

At one point, Rabbit's rap opponents beat him up in plain sight of little Lily. If it weren't for Hanson's assured, low-key realism, you'd be wondering why they didn't go all the way and tie Rabbit and his sister to the nearest railroad tracks. Too much of Hanson's energy must go into making the action believable, moment to moment, despite clanging coincidences, like Rabbit getting extra work shifts on the same night he's due to redeem himself as an up-and-coming rap artist.

Hype aside, the movie is not particularly revealing about the roots of rap: You see how it's a low-maintenance art form growing out of free-form insult games like "playing the dozens." But didn't you know that going in? The movie comes to life during a spontaneous rap around a lunch wagon. Yet even that bit is compromised by how transparently it's designed to rid Eminem of any homophobic taint.

Scott Silver, who wrote and directed the big-screen version of The Mod Squad, delivers a pack of cliches. Most of Rabbit's posse would look at home in a Fat Albert cartoon: They include a bespectacled political philosopher named DJ Iz (De'Angelo Wilson), whom the buddies label Frederick Douglass; a jovial big guy, Sol George (Omar Benson Miller), who dreams the hip-hop fantasy of Bentleys and broads; and a clueless white kid, Cheddar Bob (Evan Jones), who shoots a gun off in his pants in one shocking slapstick moment.

Hanson made an underrated ensemble coming-of-age film 20 years ago called Losin' It (it still has my favorite Tom Cruise performance). In 8 Mile, he achieves some comic traction in the group scenes; the scary-funny high point may be the shenanigans with a paint-splat gun.

Hanson doesn't attempt to imbue this film's mundane dialogue and rough-edged, hand-held camera style with the incantatory rhythms of rap. In trying not to be too MTV, he borders on the ordinary; this movie needs what Saturday Night Fever had - a sense of a new beat breaking out all over. He has muted his own talent to suit that of a star with whom he's not truly in synch.

Hanson usually has a gift for isolating key lines in a poetic aura, like Michael Douglas in Wonder Boys saying he's "taking the long way home"; here, similar lines stick out like fake summations in sitcoms. You feel you're in the hands of a master moviemaker only when Rabbit grabs his last audience and holds them in his sweaty palm.

Otherwise, you're mostly drawn to Rabbit's best friend, a warm, expansive guy called Fortune (Mekhi Phifer), the rap-battle referee who goads Rabbit into being all that he can be. The only whiff of euphoria in the movie comes from an impromptu duet Phifer and Eminem sing (to the tune of "Sweet Home Alabama") about Rabbit's living in his mother's trailer. Phifer brings a melodious lilt even to the most prosaic lines.

A star is born in 8 Mile, all right, but his name is Mekhi Phifer.

8 Mile

Starring Eminem, Kim Basinger, Brittany Murphy, Mekhi Phifer

Directed by Curtis Hanson

Released by Universal

Rated R

Time 111 minutes

Sun Score ** 1/2