You have to enable frame blending for the layer. There are 2 options: frame-mix and pixel motion. The first is probably better for fast changes as the second tries to work by using vectors and interpolating positions of pixels over the missing frames (it can result in trippy liquified acid trip effects on fast footage), timewarp does a better job with pixel motion.
Then you also need to enable frame blending for the comp, just like motion blur it won’t appear in your comp unless you say you want to see it (motion blur and frame blending can slow down rendering quite a bit). It’s between the motion blur and shy buttons at the top of your timeline for future reference.
Darby Edelen
DVD Menu Artist
Left Coast Digital
Aptos, CA