Week 11: Review Feedback, a Correction, and What's Deferred
This is a weekly update from my Google Summer of Code 2026 project with KDE, improving effect widgets in Kdenlive, a free and open source video editor.
Real usability feedback on MR !928
Julius and Bernd both tested the Speed Ramp changes and raised a genuine concern: the panel currently mixes two related but distinct ideas, time remapping (position based) and speed keyframing (rate based), without making clear which one the new curve and keyframe types actually represent.
Bernd sketched an alternative visualization plotting speed directly. Julius pointed out it would show something different from what the current curve shows, a real design question, not a quick fix.
Jean-Baptiste weighed in with a larger proposal: split the Time Remap effect into two distinct UI modes, one for Time Remap as it exists now, and a new, simpler Speed Ramp mode built around MLT's speed_map parameter instead of time_map, switchable via a toggle in the same widget.
Scoping what fits in the time left
That's a real architectural change, not something to rush into the last stretch of the program. Talked it through with Jean-Baptiste and split his suggestions into what's doable now versus what should wait:
Doable now:
- Expand the keyframe type list beyond the original curated four
- Move the Type selector into the toolbar, next to the existing keyframe buttons
Deferred, filed as issue #2231:
- The full Time Remap / Speed Ramp mode split
A correction along the way
While expanding the type list, tested what the old pre-selector behavior actually serialized as. It turned out to be linear, not discrete, correcting an assumption made earlier in the review thread. Discrete in MLT is a genuinely different shape: the source frame freezes, then jumps at the keyframe boundary, not a gradual ramp that just changes slope abruptly. Flagged the correction on the MR rather than letting it stand.
Also went back and measured which types actually cause the clip to briefly play in reverse on a time map (an overshoot artifact). Only Bounce and Elastic do it in practice, Exponential and Circular measured clean. Updated the MR description to reflect the real numbers instead of the broader guess from a couple weeks ago.
Shipped
- Type selector now offers all 13 interpolation types the rest of the effect stack already uses, instead of a curated 4
- Type selector relocated to the toolbar next to the keyframe buttons, freeing up space below the speed fields
- MR !928 description corrected and up to date with the code
- Both changes pushed, pipeline green
What's next
Heading into the final week of the program. Reviewing pending feedback across all three widgets, wrapping up documentation, and preparing the final work product submission.