Cross dissolve (not transition) ie fade two sources into/out of each other

[GME]

Howdy folks and folkettes

I'm wanting to do something similar to this, that is, two video sources (desktop and camera) fading out into each other like you see below, with similar wide feather. NOT talking about transitioning from one video to other, just a static constant split screen feathered into each other:

 

[dodgepong]

Place one source on top of the other and apply an image mask to the top source that has a gradient from white to black in the shape that you want.