The distracted camera in ''Interscope Presents: The Next Episode'' notices a dark, dangling air freshener and slants of light on heavy bags in a basement gym.

Showtime's stunning series about battle rap is billed as the reality version of ''8 Mile.'' But though the producers of the new show also made that movie, the tag line makes ''The Next Episode'' sound like nothing -- just a sorry cable effort to get the dregs of Eminem. Not true. It's so good.

Shot in a boxing gym with the rapper Xzibit as host, the multipart weekly show promises to visit rap rivalries in Atlanta, Los Angeles, Philadelphia and New York. The winners will compete against one another, rapping three ways: with a live drummer, with a beat box and a cappella. Squaring off on tonight's Detroit excursion are two fast-talking men in their 20's, Quest M.C.O.D.Y. and J-Hill.

An idle, beautiful driving tour introduces Detroit, leading the camera to city partisans, who make it clear that rap wasn't the first music in their hometown. ''If it weren't for Motown,'' one guy says, ''you wouldn't have a Def Jam.''