I have a pre-animated video and would like to change the faces of the characters but keep the mouth movements (at least) as in the original, I am hoping someone might have a possible solution, if not AE then maybe one of the other programs in CS4 or another software.
Tks and all the best
Dave Torno has a great breakdown of how he did a music video with face replacement, in which he replaced the faces of the Golden Girls with the face of the singer of the band. See this page.
Keeping the original moth movements could be done in a number of tedious ways, assuming that you hadn't planned for this from the beginning. You could use one of the Distort effects to reshape the mouth of the replacement face to match the movements of the original face.