This is a very good example of what our developers can do! There has been some preliminary work on bringing slow and fast motion to GStreamer and Pitivi, and a plugin has been created to allow for frame interpolation, which means you and I with our regular 24 frames per second cameras will be able to get smooth slowmotion from Pitivi in the future!
All that work has not yet been merged and thoroughly tested, and we need your help to make it happen!
To help you understand the difference between regular and smooth slowmotion, here is a video showing both types side by side, created by Alexandre Prokoudine. The difference is quite stunning!