Can the VSE be used to convert a 120fps video to play at 30fps? (slow motion)

Hi there,

Long story short, I’m trying to render something at 120fps, but have the vse save the exact same frames, saying it’s a 30fps file so it looks slow motion but still has every frame have movement (no frame blending).

I can set the fps in the render dialogue to 120 instead of 30 (so it’s 4 times higher). I just want the exact same number of frames, none added or subtracted, but then played back at 30 fps instead of 120. I know about the speed control effect, but can’t seem to figure out how to use the settings to get a render that happens at 25% speed while still having each frame be unique with no frame blending or stepping.

Any ideas anyone?

Yes! In fact, it can. It’s a weird feature to have in such a limited set of effects, but “Speed Control” is an option when using the add menu on the Strip window.

I don’t know exactly how to use it, but I think it’s a GUI, and pretty simple (in the video menu)

Edit: Oh, wait, sorry, I was so excited that I thought I knew the answer. You already know about speed control.

Further questions: So, you’re saying you want something rendered at 30fps, but with four frames per frame? That’s a little… uh… not possible. Could you please elaborate?

is the thing you are rendering at 120fps in the NLA? (is is video - or a blender file)

will it work if you render out 2 versions - one at 30fps and then one at 120fps? (change the scale of the NLA strip)

then you can just speed up (or slow down your audio) and pop it on over the top in the vse

might work - but I’m not 100% sure what you are trying to do

I believe this works:

Render to an image sequence (120 images)
Make a new scene
Load the sequence in an image node, connect to composite.
Set the scenes render settings fps to 30
Add the scene output to the VSE

Thanks guys,

What I’m trying to do is to render a cloth simulation in slow motion. Trouble was that rendering at 30 fps and say, stretching out 1 second of footage (30 frames) over 4 seconds meant that the image would update only every fourth frame. Frame blending is not a real fix as it just fades between images, rather than generating new ones.

@hoverkraft - your method sounds promising. Is this something that could be done in one pass (ie straight from the Blender scene to compositor to output) or something that would need two passes (output from blend scene, manually load sequence into compositor and output to final frames)? Either way I’ll play around and see what I can find. I’ll be particularly happy if that composite node you mentioned has the ability to render a scene at higher than 120 fps. Ideally I’d love to slow the motion down by 6-8 times rather than just by four times (120fps/30fps).

Anyway, thanks again everyone. I’m always amazed at how consistently helpful the Blender community is. Now to see if I can pay it forward on someone elses post. :slight_smile:

Well, if you bake and render let’s say 10sec of cloth animation at 120fps and render to an image sequence you will have 1200 frames. If you import this sequence in the VSE of a scene that has its framerate set to 30 the animation will then playback at 1/4 the speed so it will give you 40 seconds of slow-motion footage. If you render the orginal at 240fps and you will get 80 seconds.

Plus, you can directly place a 120 fps scene in the VSE of a 30 fps scene and the time will change accordingly.

Argh! Posted from my wife’s account accidentally! :o

Seems to work, just fine! :slight_smile: Shame Blender seems to limit fps to no higher than 120. :frowning:

Plus, you can directly place a 120 fps scene in the VSE of a 30 fps scene and the time will change accordingly.

Ooo! That’s what I was after - the ability to render the whole thing in one pass! Thankyou Hoverkraft!

No problem. Blender has a lot of seemingly arbitrary limits that I am not really fond of. Why, for example, has a completely floating point app every colorpicker capped at a value of 1.0, effectively restricting you to the same dynamic range as a 8 bit image…

Sorry, just had to vent.