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Nick Cannon just can't get enough of his diss track aimed at Eminem -- playing it back-to-back-to-back (and then some) -- and vibing to it harder than anyone else in the room.

Nick's been busy shooting new episodes of 'Wild 'n Out' in Atlanta this week ... and we got some footage from behind the scenes. Nick took control of the DJ booth one day, and our sources say he played "The Invitation" -- his Eminem diss track -- at least 20 times.

We're told Nick not only played the track on repeat for his VIP guests, staff and cast members, he also played it over the speakers for the audience on the main stage.

Our sources say the 'Wild 'n Out' staff is confident Eminem will eventually take the bait, and come on the show -- and 'Invitation' will become an anthem for their battle.

Important to note ... we're coming up on a week since Nick fired the first shot, and still nothing from Em -- so, the 'WnO' crew better not be holding their breath.

As we reported, Nick dropped not one, but TWO diss tracks this week. "The Invitation" took a homophobic shot at Eminem, saying, "I heard your chauffeur got a video of you suckin' c**k." Another verse, referencing Mariah Carey, "My baby mama killed you off a decade ago, You're still crying about it bitch, now who really the ho?"

Marshall hasn't said much, other than a couple tweets, back at Nick. In one, "U mad bro? Stop lying on my d**k. I never even had a chauffeur, you bougie f**k."