Setting the frame blending of your footage layer defines how After Effects re-times it.
With no frame blending, frames will be skipped at required points - you may see slight "hiccups" in the rendered footage.
With frame blending set to Frame Mix mode, AE will blend overlapping frames.
With frame blending set to Pixel Motion, AE will create new frames based on the combination of multiple frame contents. This is the most sophisticated option, and much slower to render.
Thanks. Very useful reply.
And what about dropping in a bit of 30fps video and wanting it to be the same 25fps as the composition so it goes in frame for frame? So 25 seconds of 30fps would become 30 seconds of 25fps with no lost or blended frames?
In that instance, you simply define a new frame rate in the Interpret Footage dialog. Right click on the item in the project window and choose Interpret footage.
That worked. Cheers!