Nikon D3100 grainy video?

I have had my camera for about a year now but I have only just stated making videos with it. When I record I have it on 1080p 24fps, 100 iso and on pal. I know the camera is really good I just don't know how to set it up.

I would like it to look as good as it does in this video:

This is what to does look like its just a close up of my face, i was going to try and do a black eye effect with AE:

If you play it in 1080p you will see that it looks pretty bad:/
Anyone know how I can fix this?

Reshoot with more light on the subject and use some common video techniques.

* mount the camera on a tripod
* use more lighting than just the indoor lighting as found inside homes.
* use a short script.
* make another test outside.

In order for ANY camera to shoot at 30 fps and use an ISO of 100, you must use a fast lens and if there's not enough light, the camera's ISO will have to be raised to compensate for the lack of lighting.

Most video shooters use a number of 500 watt and 750 watt incandescent lamps when shooting indoors.

NOTE: Grain is an attribute of film. What you are calling grain is actually noise generated by the camera when shooting in low light at high ISO's