I'd like to know how to get rid of the black borders that are created when I scale down or offset the x or y of a movie overlay on top of another movie. I'm using a chroma keyed video on top of another video but when I use a scale node to make the character in the chroma keyed video smaller it shrinks the whole frame and leaves black borders around the underlay video. Thanks!
The default blend type for a strip is Replace. This will replace the underlying strip with the new one, filling with black any unused area.
Change the Blend mode to Alpha over or Over drop to keep the underlying video visible. This can be set in the Edit Strip panel in the properties sidebar (press N)