In a cowshed on the outskirts of Tehran, a heavy metal band jams excitedly before a row of bewildered bovines. The barn is one of the few places where the group can play without risking arrest.

Iranian rockers’ never-ending quest for a safe practice spot is the focus of a movie by director Bahman Ghobadi. “No One Knows About Persian Cats,” which won a special jury prize (out of the official competition) at the Cannes Film Festival in May, has just opened in French cinemas, and the rights have sold in two dozen countries including the United States and Britain.

Ghobadi, 40, shot his fictional account of a real-life situation illegally, after a three-year wait for a government permit that never came. Over lunch in Paris last June, he told me he was emboldened by the bravery of Tehran’s unauthorized basement bands, and decided to make a movie about them.

For 17 days, Ghobadi led a small crew around the city, filming street scenes and band rehearsals in basements, barns, and rooftop sheds, and twice getting arrested, briefly. After dispatching his finished film to Europe, he left Iran.

For an undercover movie shot in less than three weeks, “Persian Cats” holds together well. Its main characters are a girl-and-boy indie-rock duo, Negar and Ashkan (Negar Shaghaghi and Ashkan Koshanejad, playing themselves), whose band carries the perplexing name “Take It Easy Hospital.” The pair was actually en route to London when Ghobadi turned them and a handful of other bands into the focus of his improvised script.

In the film, Negar is a brooding brunette who writes dark songs, reads Kafka, and occasionally goes to jail for performing. She wraps her hair in shawls, and wears rectangular frames. Ashkan, her subdued, bearded companion, plays keyboards, and gives Negar tips on song delivery as she rehearses her English-language lyrics at the wheel of her car.

The pair, who seek musicians to take with them to London, are shown around the underground scene by the stubbly middleman Nader (Hamed Behdad), a film fanatic who makes money selling bootleg DVDs. Nader has a bird called Bellucci — as in actress Monica Bellucci — and parrots named after the characters in “Gone With the Wind.” His shabby home-office is papered with cutouts of Humphrey Bogart and Marlon Brando.

The bands in the movie write mostly solid songs and lyrics. They dream of jamming non-stop with the gods of rock in studios stocked with energy drinks. The biggest talent among them is Hichkas (Nobody), a burly hip-hop artist who packs a powerful punch with lyrics (in Farsi) bemoaning working-class life.

While parts of “Persian Cats” seem hasty and filmed in single takes, the movie has unquestionable energy. Blending rehearsal scenes and on-the-fly shots of Tehran grit, it offers Western viewers a timely taste of life in Iran.