So there's an effect I've been pursuing for a while, and I'm not having much luck.
Basically I want to use a black & white video as a mask, and then have two additional source videos. One of the sources replaces the white areas of the mask video, and the other source replaces the black parts of the mask video.
I thought what I could do is place the "mask" video on Layer 4, with the "white" video underneath on Layer 3, and set the Multiply blend mode. (This part seems to work).
I then placed a Layer Router on Layer 2, asking it to take Layer 4 as the source. I added an Invert effect to flip black and white. So far so good.
I then placed the "black" video on Layer 1, and set the blend mode on Layer 2 to Multiply. Doesn't seem to be working. Any thoughts on why this might be the case? I've attached a screen shot of the setup.