Duplicate the footage layer, name the top copy "Stabilized"
Add Mocha AE to the bottom copy of the footage, draw a spline around the cat's mouth, track Transform, Scale, Rotation, and Skew (not perspective), name the layer Stabilize, and save the track
Return to AE and Spin Down "Tracking Data" in Mocha's ECP (Effects Control Panel)
Click Invert in Tracking Data, Create Track Data, and choose Stabilize
Under "Export Options," choose Stabilize, then Choose Transform from the Export Options and apply the tracking data to the Top "Stabilized" layer
Preview the track - The cat's mouth should not move. If it does, repeat the track until you get a good one
Pre-compose the top "Stabilized" layer, moving all attributes, and find a frame where the cat's mouth is open. Apply a mask around the cat's mouth to get something you can animate
Apply Layer/Time/Freeze Frame to capture the cat's open mouth, then Pre-compose again, moving all attributes, and name the layer Mouth
You should now have a layer of the cat's open mouth that does not move and stays in the same position on the screen
If the mouth does not move, pre-compose again and name the layer "Puppet," and use the Layer/Open Layer menu to open the Puppet layer in the layer panel
Use Puppet Pin to animate the mouth
Return to the Main Comp, select the footage layer (with Mocha applied), and turn off Invert in the Tracking Data area
Make sure that the Puppet layer (layer 1) is selected and Transform is selected in the Export Options and hit apply
You should be done
If you already have an animated mouth and the layer is in the right position on frame one, you can apply the Transform tracking data from Mocha directly to the animated mouth layer.
I do this kind of thing all the time. If you get a good track, your animated mouth will stick to the cat's face as the camera and the cat move.
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