Make blurred background lighter on resources

[bjoern-tantau]

When I blur my background the video begins to drastically slow down. Using a background image or green screen has no such problems.
As a workaround I took a photo with the webcam, blurred it in Krita and used that as the background image. The visual effect is the same, but it's much lighter on resources. Maybe fakecam can offer the same and just take a new image to blur about every second or so.