Though it’s about an overweight white New Jersey girl who wants to be a rapper and is done up in a harsh visual style, Geremy Jasper’s “Patti Cake$” proves, in the end, a surprisingly conventional movie about chasing your dreams—contrived and more than a little unconvincing, but energetic and well-acted. The animated kidflick “Leap!”—which is being released simultaneously—may be tonally very different, but the two pictures carry a similar message, and in neither case is it terribly credible, even when sporadically entertaining as it is here.

The title character is Patricia Dombrowski (Danielle Macdonald), a chubby devotee of the hip-hop world who lives in lower-class squalor with her slatternly mother Barb (Bridget Everett) and frail but supportive grandma Nana (Cathy Moriarty). Dismissed as Dumbo by her street nemesis Slaz (Patrick Brana), a pizza-guy-drug-dealer with rapper pretensions of his own, she works as a bartender in a run-down place where locals perform, among them her mother, who relives her glory days as a singer whenever she can, even teaming up with a cop who’s put together a cover band.

Patti idolizes O-Z (Sahr Ngaujah), a producer-performer she dreams of becoming her promoter, but her only fan is Hareesh (Siddharth Dhananjay), a pharmacy clerk and guitarist. She has a kind of epiphany, though, when she encounters Basterd (Mamoudou Athie), a brooding singer who calls himself Antichrist and performs a cutting-edge act that leaves everyone at the bar but her cold. She follows him back to his hideaway in a cemetery—a shack filled with recording equipment—where, along with Hareesh, they will eventually lay down tracks for a demo CD for their newly-named group PBNJ (and yes, they are aware that it’s an antiquated means of getting your music out there).

That will lead to a gig Hareesh engineers at a nearby strip club, but it doesn’t turn out terribly well. More successful, at least for a while, is the job that Patti secures at a catering service, where her mixologist expertise pays big dividends—until the outfit is hired to staff a bash at O-Z’s palatial crib. PBNJ’s appearance at a contest where he serves as a judge will bring one of those triumphant moments that, in this genre, turn to ash—until the worm turns again. And what of her mother, who until this moment has been dismissive of her daughter’s ambitions? What she does will come as no surprise, either.

“Patti Cake$” has its heart in the right place, and the cast play it for all it’s worth. Macdonald carries the brunt of the film, and gains audience sympathy for the character’s plight, while Dhananjay and Athie give heft to Hareesh and Basterd even though both come across as walking screenwriter’s inventions rather than authentic human beings. The same can be said of Everett, who resembles one of those kitchen-sink types familiar from a certain sort of British drama but has the ability to take charge of a scene.

The actors’ energy owes a good deal to Jasper, whose background in directing music videos surely came in handy here, giving him tools that help to bring the musical sequences to life. But he handles the dramatic elements decently as well, even though the scenario he’s crafted is a matter of putting old wine in new bottles. The picture certainly looks right, with Meredith Lippincott’s production design and Federico Cesca’s kinetic cinematography combining to create a convincingly gritty, pulsating ambience, while Brad Turner’s edgy editing contributes to the overall on-the-move feel.

Jamie Kennedy once played a rich white boy who wanted to be a rapper. Happily Jasper’s picture is no “Malibu’s Most Wanted.” While far more formulaic than it pretends to be, “Patti Cake$” has enough going for it—including Macdonald—to be worth a look, as long as rap doesn’t completely turn you off.