I was trying to do the subject mentioned task by importing a short video into Photoshop. While I can move the gradient layer mask in any direction, I don't seem able to rotate it and have the rotation controlled by keyframes.... so I am trying out After Effects.
The first question I have is: how can I create the same kind of curves gradient layer mask in AE? It is a reflected gradient, so the effect from the downward curve is most prominent at the edges of the frame and brightest in center (sort of like vignetting). I think once I can get this going, I can then go from there.