Blur video in after effects

Even if you're not sure what you're precomposing, make sure the precompose is large enough that the quality of the elements inside it isn't reduced and you don't have to turn on continuous rasterization.

You get what you ask for. Enabvling continuous rasterization changes rendering order and layer transforms. The rest we can't know since you have not offered any screenshots or otehr useful info. From your tracked camera simply having DOF to the mesh warp degrading the footage to a million other things like hardware acceleration issues this could be anything. In any case, more info is required and just to preempt your disappointment, you likely will have to start over using a different methodology.

Mylenium