I didn't listen to the vid. Mist some water on the belt, if the noise goes away you have belt noise. The pulleys get glazed and make a chirping sound. The occurs more often on flat belt system where the smooth back of belt idler has more surface area.

Sand the pulley with 80 grit paper to make a slightly roughen the V grooves of the pulley.

As for a pulley failing, the only way to tell is remove and look for cracks. On a steel pulley there will generally be a line with powdery brown rust along the crack. This is from fretting of the crack.