I have two videos, one taken with my iphone which is moving around a building face and one over my shoulder following my iphone. I am trying to put the video taken with my iphone onto the video taken over my shoulder but when i create a mask the area keeps changing when it is following the motion tracker? Please help quick, deadline is tomorrow!
Precompose footage of the phone you need to mask. Then put your mask on the pre- comp . When you stabilize footage you are moving it around so the mask moves with the footage. If this doesn't help then I don't understand your problem.
Advancing to the next problem you will have, making the masked video appear to be nailed to the iPhone. You'll open the AE help system and spend a few hours stydying and experimenting with motion tracking to figure out how to track the corners of the iphone's face and then apply that data to the masked layer so it moves with the iPhone.
Nothing complex about what Rick has told you but there are about 100 pages in the manuals dedicated to motion tracking and its variations. MAybe another 100 pages to the advanced applications. Literally hudnreds of tutorials available in books, sites and vimeo/youtube.. IN fact, peopel have been doing iPHone inserts since the iPHone1 and iOS1 were released; nothing new, plenty of stuff available online.
Might be easier to reshoot the scene with aother iPhone off cmaera runing facetime in realtime.