Hi... First of all..

Fact - 1 : N9 cannot play HD / High resolution videos.
Fact - 2 : I still love my N9 like anything.

No point in spending 20 pages time for something which is not available for now on your phone.

For YouTube lovers.. Simply use Cute-Tube app (YouTube client for N9). This is simply best & allows to download / play videos.

Since its meant for N9. It will download videos with best possible resolution compatible for N9 (and will play in full screen mode, to be noted)

Case Closed.