software for frame images to video with changing framerate?
This is a really late response but I just stumbled onto the question.

The software you're looking for is Adobe After Effects.  

Inside After Effects, you'll end up using the effect called "Time Remapping".


Open After Effects
Import all your frames as an image sequence
Create a composition(whatever resolution/framerate you'd like)
Drag your image sequence into the comp(or timeline)
In the effects panel, find the time remapping effect and drag it onto your image sequence
Go to the effects tab and it should show you the time remapping effect.  Add a keyframe using the stopwatch
Add as many keyframes as you need and adjust them to the speed you want depending on where you're at in the video
When you're ready to move to the "graph view" select the "graph editor" button


If you're having trouble just google "Time Remapping in after effects" and "Graph Editor view in After Effects" and you should find what you're looking for.