Mapping background video over mesh

I am trying to create a talking animal short where I use video of a cat. Create a mesh head of the cat and animate the mouth.

However, I can’t figure out how to re-project the video back over the mesh and then match it to the same video in the background.

This technique was used in the kids movie “Racing Stripes”.

Any ideas please?

You just need to add your animation over the video by using alpha Chanel in compositor.

Thanks for your reply.

But does this map the video over the mesh in exactly the same screen co-ordinates as the background?

Is there a tutorial somewhere for this?

The background image in the 3D view will display stretched to the camera size. The Compositor can do that too. If all sizes match then there will be no problem.