Also check the water pump, alternator, and PS pulleys the next time you take the belts off. If they have lateral play or rumble/grind when you spin them by hand you may have a component about to fail. I'm not quite sure why but my first thought on hearing the video was failing water pump. If everything else seems fine just replace the tensioner and idler pulleys and you should be good to go.
04 IR 330i ZHP | ESS TS2+ SC | MagnaFlow "headers" | KMS 3.64 LSD | AST 4100 550/650| APEX ARC-8 18x9 | H&R front sway bar | Vorshlag camber plates, RTAB limiters | TMS subframe & swaybar reinforcements | UUC SSK & DSSR | UUC TM & TME | BW motor mounts | Dinan strut & shock tower bars | vaio 4-bolt oil pump