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Acheiving smoother animation using DAIN, RIFE etc.

The Scribbling Man

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So I'm a layman with a lot of the technical side of framerates etc., but bear with/humour me while I lay out my predicament.

So for a while I've been experimenting on and off using DAIN and RIFE and creating new frames/increasing framerate, both as ways of fixing jump frames and also in order to improve animation. You can see examples of people doing similar things using the same software online:

This has been producing some great results for me in particular circumstances, but there are others where I'm a bit stumped as to how to get the desired result/whether the desired result is actually possible. Additionally, examples like the video above are simply of putting entire scenes through the software and doubling the framerate. Playing everything back at 60fps is not the same as achieving smoother motion at the original framerate, if you get what I mean? Plus, I don't actually like the look of high framerates - it feels unnatural in the context of a film.

So here's a hypothetical:

For the sake of maths ease, let's pretend you're looking at a film that's in 30fps. Let's say we have a live action scene with stop motion animation effects, and while the general motion of the film is as smooth as you'd expect it to be, the animation FX are noticeably jittery. You realise that while the live action footage might be playing back at 30fps, the animation fx only move every other frame, so are in effect playing back at 15fps. So, by:

  • dropping the null frames on the animation (effectively doubling the speed)
  • rendering it out at 30fps
  • doubling the framerate of that footage to 60fps
  • importing that footage back in and halving the playback speed to 30fps

...you then get the same animation playing back at the same speed as before, only with the null frames replaced by newly invented ones that allow for visibly smoother motion. This allows you to pair smoother animated footage with the live action footage.

Awesome.

Ok, so here's scenario B, which I also come across and don't know what to do with.

Scenario B is the same as above, except the animation both looks jittery AND is at a framerate consistent with the rest of the footage. AKA every frame shows movement.

So, you can render that animation out and you can double, even quadruple, the framerate with incredible results; but none of this will matter, because your source film is at 30fps and needs to stay at that consistently.

So I guess my question is, if I increase the framerate of a piece of animation in order to make it look slicker, is it then possible to somehow translate that newly achieved "smoothness" back to the original framerate for slotting back into the source footage? Or will I inevitably always be discarding the very same frames that were created to make it smooth in the first place? Is there any way around this? Obviously one can halve the playback rate and get some wonderfully smooth motion from the animation, but it will also be at half the desired speed...
 

Captain Khajiit

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So, you can render that animation out and you can double, even quadruple, the framerate with incredible results; but none of this will matter, because your source film is at 30fps and needs to stay at that consistently. So I guess my question is, if I increase the framerate of a piece of animation in order to make it look slicker, is it then possible to somehow translate that newly achieved "smoothness" back to the original framerate for slotting back into the source footage?
My instinct is to say no: if the animation is jittery at the frame-rate at which it was composed, it will probably always be jittery at that frame-rate. Smoothing out the motion by doubling the frame-rate through frame-interpolation is no good if the interpolated frames are discarded when conforming the footage to the original frame-rate, unless maybe you truncate (top and tail) the shot instead, allowing the smoother portion that was originally the middle to take the place of the whole shot. That's probably not ideal though.

A couple more ideas:

Approach 1

Decimate the clip in question (30fps to 15fps). Apply frame-interpolation (15fps to 30fps), and hope that the interpolated frames are smoother than the originals (the ones lost in decimation).

Approach 2

Use frame-interpolation to go from 30fps to 15fps (in other words, reducing rather than increasing the frame-rate via interpolation), thus throwing away all the original frames and constructing new (hopefully less jittery) ones. [EDIT: This could be done in AviSynth-based frame-interpolation methods, but I don't know if it's possible with the tools that you are using.] Then use frame-interpolation a second time to go from 15fps to 30fps, the desired frame-rate.

I hope that this gives you a few ideas and that I've correctly understood your problem.
 
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The Scribbling Man

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Approach 1 has actually worked really well. Thanks again for the advice!
 

Captain Khajiit

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You're most welcome. I'm pleased to hear that one approach worked out well, especially given that both ideas were largely theoretical on my part.
 
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