Overlay still image over face video : Adobe After Effects

Hi,

I am fairly new to AE and to this forum, so first of all I want to thank for all the help you guys have given and give to people like me. :)

I have checked a few face replacing/masking tutorials (including the great demon video and the Golden Girls from Adobe) but I don't think that's quite what I am trying to do.

I have a video of a person (it's not a wild shot, the face is pretty steady and doesn't move all too much... just talking). And I have the still image of another person.

Is there any way to overlay the still image over the video face so that the original speaker is not seen and instead the still image "speaks"?

I am quite aware of the fact that this won't look very professional (if it's possible at all) but that wouldn't be a problem. In fact, the intention is to give it a rather unrealistic look so it wouldn't matter much if the (then) "animated" still picture looks odd.

Could you maybe define specific tracking points on both faces and link them together... and then make the overlaying picture... well, sort of move along the underlying face's tracking points? Of course, the mouth part of the still mage should then be a bit more flexible... so that it can be opened and closed depending on the video face's mouth movement.

I'd appreciate any hint in this matter... and it wouldn't matter if a solution is quite complicated. :)

Thanks in advance.

P.S: I have also though about the annoying orange way... but that doesn't seem to be doable in my case since there are quite big differences between the faces, the beard of the video face being the most important one.