I'm working on a green screened project and am scaling my foreground video then passing it into a keying node, then alpha over. The problem is, the area outside the scaled video is black not green, so it ends up masking out the background video. Is there a way to make the area outside the foreground video be alpha?
At least in this case, adding a mix node between the scale and keying nodes that mixes the foreground video with the green screen color extended the green color to the original size of the foreground video.
This raises the question of what if your background video is larger than your foreground video to begin with.