Here's a sample of how the final product should look. At the end of the video it will "un-split".
(1) You may use these clips a-roll and b-roll (right click, save target as). Look on video drive first, someone else might already have downloaded them.
(2) Follow steps 1, 2 and 3 of Letterbox Mask , except do not add points 3 & 4 on the gradient.
(3) In steps 4 & 5 of Letterbox Mask, use the a-roll and b-roll clips you downloaded in step 1.
(4) Now let's animate the mask. You're going to use four keyframes.
Above you see the first keyframe. Note that gradient points 1 and 2 are in the upper left corner.
Below is the second keyframe. Now gradient points 1 and 2 are nearly in the center.
Keyframes 1 and 2 are very close together so that the screen will be split quickly.
Copy keyframe 2 and paste it in the spot just before the girls hang up the phone. Copy keyframe 1 and paste it just after keyframe 3.