That sounds like what I was thinking of. The recovery of hidden pixels
sounds like the biggest problem. I'm starting to think that maybe this
could be overcome by taking a sequence of shots where the whole object(s)
is in view at some point then all the objects can be whole morphs and then
composed. Or perhaps where there is motion like someone walking through
water it would be a composite. 

Thanks
Gary


>Gary,
>
>what you are after happend to be the most dramatic change in MPEG-4 
>compared to previous standards. Those considered a movie to be a 
>sequence of rectangular images, all the same size. In contrast, MPEG-4 
>thinks of a movie as a composition of objects (using a VRML inspired 
>scene discription "language"), each of which is a sequence of irregular 
>images.
>
>Obvious decoding such a system is easy - expand each object and layer 
>them one over the other. Encoding is easy for synthetic material, like 
>a computer generated cartoon. Encoding existing video is *very* hard 
>since it would involve segmentation, recovering hidden pixels and other 
>problems that happen to be interesting to you. When the standard was 
>created in 1999 it was hoped that these problems would be solved 
>eventually and the decoders would be ready. I don't know what the 
>popular MPEG-4 encoders, such as DivX;), do but I imagine they don't 
>try to separate the images at all.
>
>In another email you asked about separating MP3s into tracks. With 
>recordings that put some instruments on one channel, the rest on the 
>other one and the vocals in the middle (equally on both) you might be 
>able to separate the voice with a little signal processing.
>
>Good luck,
>-- Jecel
>