ugh, loose loud knocking sound. Loose headset?? *video*

Could be loose headset

or loose bearings

or loose stanchions


The last one is the worst

The first one is the best

Use some scientific method to figure out which, if you can adjust the tire from side to side, then the bearings are loose or maybe your axle is bad (manufactured to low tolerances)

take the wheel off and let the forks sit on somthing solid. slowly and lightly raise/lower/fiddle with the handle bars, not at all like how you did in the vid, make sure the fork lowers remain on the surface. If there is movement, but the fork lowers remain on the surface, then the headset is loose.

Put your hand under the lower crown and lightly bounce the front up and down, you will feel the play if it is a loose headset.

Remove the wheel and reinstall the axle. step on top of the axle, push down and bit then pull up lightly. You will hear and feel the play in the lowers if it is your bushings or a fork problem.

Try the video again without you slamming the tire into the ground, I hear to much of the wheel slamming then I do your problem.

Pull the fork, pop out the headset cups, clean, relube and reinstall. Reinstall your fork and make sure that the crowns are tight to the headtube like they are supposed to be.

Remove the wheel and the axle. Keep the tire on the ground and install the axle in the hub, move the axle around the hub to see if the bearings are loose or there is a problem with your hub.

Back off and then tighten all bolts on your bike to proper torque specs.

There are many things that it could be but it is hard to give you specifics just by listening to it on a youtube vid.

Swing by your LBS and let them do what they get paid to do.