Keyframes -> spline based interpolation ?


how about spline based interpolation between keyframes ?

The current linear interpolation gives very poor results, especially when it
comes to any sort of motion (Ken Burns effect, etc.). This is mainly caused by
the non-continuously differentiable nature of piece-wiese linear defined functions.
In terms of motion, we end up with infinite peaks of acceleration at the individual
keyframes and end up with obviously jerky camara movement.

In other tools like cinelerra, a spline based interpolation is default and picewise
line has to be activated intentionally. Consequently, the results of any keyframe action
is way smoother.

I'd vote for a spline based keyframe system in Kdenlive, giving it highest priority.
What do the main devolopers think ?
Is there any work in progress improving the keyframe system ?

By the way: Is there a central keyframe framework re-used by all effects, or are keyframes
handled by the effects and transitions individually ? (I hope not ....)


This would be a great addition to Kdenlive (if it's possible to do)!

I currently use a script called Diascope ( which produces a nice spline-based Ken Burns style slideshow out of still images, but it would be great to do this natively in Kdenlive. Spline based movement looks extremely professional as it's possible to slow down / speed up the rate of zoom depending on the subject matter in the photos. I've found it's quite difficult to incorporate still images into a video without having some configurability over the pan/zoom movement. The current linear keyframing of the "composite" transition looks somewhat out of place for some subject matter when trying to achieve a Ken Burns effect (e.g. panning across a school photo and coming to rest on an individual).

I fully agree that spline based interpolation is a high priority issue. It's such a "simple" feature, but it can greatly increase the quality of a video.

Here's another vote for this feature. I had not heard this term before or that it was available in other FOSS applications but I've posted elsewhere on this forum about my desire to see improvements in the smoothness of pans and zooms. I hope it can be included in Kdenlive in the future.

This feature needs to be implemented in MLT, our video framework. Currently, keyframes in MLT only allow linear interpolation, so we cannot have better in Kdenlive. Improved keyframes are on MLT's roadmap ( - called PropertyAnimation), but Dan Dennedy - MLT's maintainer - is currently busy working on some core parts of MLT, so I don't know when he will have time for this.

But for sure this is a necessary feature.