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VSE: keyframed Speed Control strips acting on Scene strips interfere with other keyframed strips
Closed, ResolvedPublic


System Information
Windows 10

Blender Version
Broken in both 2.79b and 2.80-41cba97


I was using the Video Sequencer to edit an animation. I had a Scene strip, with a Speed Control strip attached to act as a freeze frame -- I keyframed the speed factor so it would jump between 0 and 1 to pause at certain points. And I had some moving image strips overlayed on top of this. I noticed that the movement of the image strips would jump every time the speed changed, even though the speed control strip wasn't connected to them.

Steps to reproduce
Here's a simplified file with the bug:

The text is supposed to move up and down the screen smoothly. But when you play the sequence, the animation jumps in the middle, right when the speed factor of the speed control strip changes. Sometimes the text jumps at other points too.

Steps to reproduce

  • In the Video Sequencer, add a Scene strip.
  • Add a Speed Control strip connected to the Scene strip.
  • On the speed control strip, uncheck "Stretch to input strip length" and check "Use as speed." Change "Multiply Speed" to 1.
  • Add keyframes to the Speed factor so that it starts at 0, and at some point has a Constant keyframe that jumps to 1
  • Add a text or image strip on top of the scene/speed strips. Add keyframes it so it moves. When the Speed strip's speed changes, the text/image animation will reset.

The bug still occurs even when I select a different scene than the one with the sequence.

Event Timeline

Philipp Oeser (lichtwerk) triaged this task as Confirmed, Medium priority.

Confirmed (without further investigation in code so far)

Strangely enough: if you

  • mute the Speed strip (H) and let the animation run through the timeline once
  • unmute again (Alt+H)
  • cant get it to fail after that, everything is fine then

needs further investigation...