unfocused/blurry background

I need some help. Using gknot and tried a couple of different filters, but can't get the background to look good. The focus of the camera looks sharp and fine. Anyone who can give me a hint on what i can be done/ what filter to use? J

Hi- What resizing filter are you using? Maybe try a sharper one if possible.

Mostly using neutral bicubical, tried others but i cant se much difference. Will try sharp bicubical once on this ep and compare the two .avi ... thanx for taking time to answer my question J