I have started playing with split screen options in Premiere CS6, and I understand how to split the screen, incorporate a graphical mask to split the two screens (white bar), and animate the clips so they move onto the screen.
What I haven't been able to find online tutorials is how the below video is able to "reveal" the larger clip as the white bar moves across the screen. The clip underneath doesn't scale/resize/move, it is simply already there playing. As the white bar moves across the screen, it wipes what was originally on the top layer, and reveals what is underneath.
Any tutorials or tips you can share to point me in the right direction of learning these techniques?