It's Autotune with very fast retune speed, trust me.
They just used the talkbox in the music video to replicate the 70s-80s era funk music videos.
The talkbox is what Roger Troutman & Daft Punk use (Dafts is computer generated)
This whole song is composed from a Talkbox (Scott Storch)
They sound similar but very different when heard side by side.
You can't hear the singers natural voice with the Talkbox, opposed to Autotune.