I do a fair amount of time manipulation of video footage and I've been using Interpret Footage to change frame rates. But I'm wondering what, if anything, is the difference between that method and stretching/contracting the footage using Stretch function in the timeline.
Photographer / Motion Graphics Artist
With interpret footage you are setting the footage/sequence to run at a different frame rate. So the duration changes but you are seeing every frame there is. When you are time remapping the footage AE (or whatever program you have) will need to create or remove frames.
So for example if you edit 24 fps footage to a 25 fps sequence without interpreting it there would be an extra frame at the end of each second to keep the duration the same. Editing a 60 fps footage into a 30 fps sequence would drop every other frame.
It depends a lot on the kind of time manipulation you're doing and your tolerance for herky-jerky video.
Like to work at 29.97 and want a little slo-mo? Shoot at 59.94, conform to 29.97 in Interpret footage settings, and you have great-looking half-speed video. It's always best if you're speeding up and and slowing down in integer increments.
But if you're speeding up/slowing down at off the wall values like 138%, 22%, 73.5%, etc. you might want to look at using AE's Timewarp effect. I think you'll find it works better than just stretching. You'll find it under AE's Time category of effects, amazingly enough.
KGAN (CBS) & KFXA (Fox) Cedar Rapids, IA