Don’t be surprised if, settling into “The Last Five Years” with your popcorn, you hear a large number of people around you singing rather than crunching.

That’s because the stage play it’s based on, a soulful and romantic song cycle by composer Jason Robert Brown, is a cult favorite of musical theater aficionados, not to mention a preferred source of audition songs. Most recently revived off-Broadway in 2013, it’s the charming and ultimately mournful story of a five-year relationship, from its giddy, heady beginnings to its depressing end.

Only here’s the twist: The woman’s journey starts at its somber conclusion — a Dear Jane letter — and moves backward in time to its sunny early days. The man travels forward in time, and the two meet, chronologically speaking, only in the middle, for a marriage proposal amid the majesty of Manhattan’s Central Park.

Alas, that clever structure doesn’t work nearly as well in this screen version, adapted and directed by Richard Lagravanese and starring Anna Kendrick and Jeremy Jordan as lovers on opposing trajectories. That’s because it’s just too darned confusing.

Of course, the main attraction is the score — there’s hardly any dialogue — and Brown’s melodies are truly infectious.

And the film does have one asset the stage production didn’t: a bona fide movie star in the fast-rising Kendrick, who cut her teeth in musical theater and is, not surprisingly, charming and quirky and altogether irresistible as Cathy. As for Jordan, the Tony-nominated star of “Newsies: The Musical” and TV’s “Smash,” he’s drop-dead handsome and has a great singing voice; If he doesn’t match his co-star in the charisma department, it’s not really a fair fight.

Jordan’s character is also far less sympathetic. A young literary prodigy, Jamie has dropped out of Columbia and is having his debut novel published. Such a thing can go to a guy’s head, and it does. He loves Cathy — “Shiksa Goddess” is an amusing ode to her goy loveliness — but he seems to love himself an awful lot, too.

Cathy, meanwhile, spends her days waiting hours in line to audition alongside younger and thinner women.

Marriage comes at the midpoint: “Will you share your life with me for the next 10 minutes?” Jamie asks in a glorious duet. When things fall apart, we should perhaps feel sadder, but remember, at the end, things are falling apart for only one of the lovers. Cathy is flying high, because she’s just met Jamie, and so her lovely “Goodbye Until Tomorrow” is really just a happy reflection on a great beginning. “I will be waiting,” she sings confidently. We will, too — to hear Kendrick sing again. In anything.