Its probably the idler pulley bearing, but it could also be the compressor clutch bearing (the compressor bearings aren't even turning unless the clutch is engaged, which it obviously isn't in that video).
To isolate a bad bearing on a belt driven accessory, you pretty much have to remove the belt and spin each driven pulley by hand until you find the one that feels rough or has obvious play in it. You can also use an engine stethoscope (or a piece of rubber heater hose works fairly well) and touch it to the mounting bracket of each accessory. Problem with that is that the sound conducts through all the brackets and its hard to find the one that's really the loudest.
"You can always tell how long a vehicle is made to last by how many zerks are on the wear points." - SteveSRT8, on the Oil Guy forums
2001 Cherokee Sport automatic (snore) 2wd (yawn) ultra-reliable commuter vehicle
1999 Cherokee 2door 4x4 5-speed (daughter's)
Two big-block Mopars, and a Ram 1500