Creating b&w-shape based transitions between two videos
I would like to transition from one video to the next by using an black & white animated video mask. I'm having a very hard time using proper terminology and it's getting in the way of my web searches, so here's a picture that should clarify things:

I know that I can do this in After Affects, but can it be easily accomplished in Premiere? It would be speedier, work-flow wise, if I could do it there.
Thanks for your attention.
