I'm using Blender's video editor to overlay an image on top of my video footage. The problem is, I need to mask (make transparent) certain parts of the image that are currently blocking part of the video at certain frames. I am able to create a single frame mask and apply it to an adjustment layer that works as exactly as intended by showing the underlying video. I was able to create an animated mask in the movie editor, but when I apply it to the adjustment layer the mask doesn't work at all. I compared the strip settings of both the single frame and animated masks and they are identical, both using Alpha Over as a blend mode. I followed this video tutorial (times 7:22 - 9:22) but the animated mask is still not masking at all. I'm not sure what I am doing wrong.