I made an animation in 24 fps and when I render it, I see quite a few bits that are choppy, rendering in 30fps would improve this. The problem is that makes my movie shorter. To keep it the same length I would have to obviously increase the number of frames, but I would then have to shift all my keyframing by different amounts. Is there any way to automatically adjust this?
Beneath the Frame Rate dropdown in the render panel, there is a time remapping section. Set the old mapping to 24 and the new to 30. For more in-depth info, see here: http://www.ffnn.nl/pages/articles/media/blender-tips-and-tricks.php
I found a relatively easy way by going into the dope sheet, selecting all, scaling by 1.25 (to go from 24fps to 30fps). Then grab all points and slide so the first keyframe is at frame 1 again. Then set the end frame also to 1.25x the original frame length.
You can render at 30 fps, then bring it into the compositor and render it out as a movie at 24fps. You also could in the graph editor scale all of your key-frames in the x-axis, you would have to extend the render end frame.