How to? Workflow for VSE with Speed Control


Blender 2.75a: in the VSE, I added a movie which was recorded at 50 Hz. My video output should be at 25 Hz. Therefore I added a Speed Control to the video strip, with the following settings (see

Now I want to use only some parts of this strip; i.e. I want to cut it to several strips and use only some.

When I cut the video strip, the speed strip doesn’t get cut into two pieces but will only be one piece. Furthermore at the point where the cut is, the frames of the video will not match anymore.

My idea now was to make a meta-strip of the video strip and the speed strip. This works as long as I do not un-meta the strips. If I do so, the strip lenghts will be expanded to the uncut length.

Therefore I wanted to ask if anyone has a good and working workflow for this.

Best regards

Can you not edit your footage and then add any speed adjustments to the whole edited version to keep things simple

Hi, thanks for your suggestion. However, if I do not do a speed adjustment in the first place, video and audio are out of sync.

Of course I could render out a non-edited version just using the speed strip, then create a new .blend file and import the re-sampled movie and edit this. But that’s not a workflow. That’s a (bad and time-consuming) workaround.

Sorry Blender doesn’t really have a tool set for retiming video. As Richard says above you either speed effect a group or regenerate all media at new frame rate. Blender is not temporaly aware so it assumes correct frame rate of sources.

Well this is Blender so guess what? It’s doable! :slight_smile:

Have a look at this video:
where the creator, Marius Oberholster, posted a most interesting discovery.

It sounded too good to be true so I bookmarked it to test it out more systematically with various frame rates. Now, the question in this post prompted me to dig out an old summer bookmark.

I went ahead and tested it with the latest git master: I imported 5 clips of different fps and set the overall project rate to 23,98. Some of the clips had lower fps, some higher, and to my surprise everything worked seamlessly!

Then came the moment of truth: cutting the clips. I converted all relevant clip strips (i.e. video, audio, speed) to a metastrip, then cloned the scene, sliced the strips randomly (all soft cuts), and deleted some of the clips. Playback was sweet after cutting, I noticed no sync errors, and rendering out went fine too.

Now all that is needed is replication to make sure this works across formats, various frame rates and codecs. Workflow optimization tips might also be needed (e.g. it might be safe to cut on the spot wo duplicating the scence). More testing is required to ensure that this is indeed reliable.

Kudos to Marius for an outstanding discovery.

ps: I only wonder how many hours I have wasted coverting clips to the desired frame rates using other apps. I suspect that this might have been possible for a long time and nobody noticed…

Umm, not sure what is new here? Speed strip effect has always defaulted to “stretch to strip length”. The issue is that Blender drops frames to create the speed change and cannot blend them for smooth playback.

And the OP was referring to the way other NLEs will auto stretch the incoming frame rate to match project frame rate.