The filming took place during a typical backup operation from the host to the tape drive. There was nothing in the test that could be considered outside the limits of normal use of a computer and tape drive. The view focuses on the motion of the internal take-up reel that winds the tape from the cartridge. Forward tape direction is clockwise rotation. While the drive writes data, the reel rotates clockwise.
Reverse direction is counter-clockwise rotation.
In the video, the reel repeatedly runs out of data from the host. Each time, it must reverse direction, stop, and then wait for mor data before it can accelerate back to speed and resume writing. The video was shot looking down from above on a device very similar to the one shown in the illustration below. What you see spinning in the video is the internal take-up reel, which is the the reel in the top right hand side of the illustration. The tape is fed from the cartridge on the left and winds around the take-up reel.