[VSE] What is wrong with Speed Control? (And why?)


I tried to convert a video’s framerate using Speed Control, but it doesn’t work as expected. Let me explain:

My video input file is, for technical reasons, recorded at 50.16 fps. This is not a very nice framerate to use, so I wanted to scale that down to a more reasonable 30 or 25 fps. I’ve done this in the past in Blender 2.4, just import the video while at the desired output framerate, then use Speed Control to match the video with the audio length. Turn on ‘frame blending’ for smooth results and that was the end of the matter.

However, I tried to do the same thing the other day in Blender 2.67 and 2.68. To my astonishment, ‘frame blending’ has been gone for a long time. Why is a function, that worked perfectly in 2009, suddenly not available anymore in 2013? Well, there’s workarounds for that, I can just scale it to 100 fps and use a custom made application to blend the frames back to 25.

But, when I tried that, the video wasn’t sync anymore. It drifted. After careful examination, it appears Speed Control does not alter the video’s speed linear anymore. And there’s no way to correct that. I cannot just add a 0-100% linear curve in the F-Curve Editor anymore, the ‘Use as speed’ and ‘Scale to length’ and ‘Frame number’ options don’t appear to work correctly at all

So I was wondering: what is wrong with Speed Control? This worked fine in 2.47, but somehow is completely butchered in all newer version. Why?

For those wondering: the solution to my problem was to just start up Blender 2.47 again and scale the framerate in there. It’s ridiculous though how much older versions I need to keep, I’ve got 2.4, 2.5 and 2.6 installed, just because you never know what feature gets deleted next time.

Have you tried reporting the bug? Be sure it isn’t already a known issue b4 posting via a search:


I had the same issue about a year ago but I just thought it never worked.

Did you build a proxy timecode first? This often fixes decompression frame handling issues. Or you could transcode the source footage to a more blender friendly format.