F-Curve and Speed Effect Strip (time warp modifier)

I am trying to use Blender as video editor and I want to create smooth speed changes. I expected it to be rather straightforward:

  • add Speed effect strip on top the strip I want to modify
  • create F-Curve to control “Multiply Speed” property

But I can’t seem to get the F-Curve for it be created. When I press “I” when hovering over other properties I get F-Curve appear and color of the field changes. But nothing happens for “Multiply Speed”.

What is the proper way to achieve time warp/smooth speed change in Blender video sequencer?

In the Effect Strip settings deselect the ‘Stretch to input strip length’ tickbox. This will then show a Speed Factor slider which you can then keyframe. It is a bit flaky but I’ve just tried it and been able to adjust the playback speed in the graph editor


Exactly what I was looking for. I don’t think I would ever find that I needed do disable “stretching”.
It would be even better if there was a way to map “input movie time” to “output movie time” instead of speed factor.

And I just found that. It would be great if Blender speed effect could use it for slowing down videos.