Make Your Animation Smoother with Video Frame Interpolation!

One thing that makes stop motion animation special is that it's imperfect. The jittery movements and sometimes even the minor errors that animators make allow for a more authentic experience that you can't have with CGI.

(Fun Fact: Aardman Studios, responsible for creating masterpieces such as Chicken Run and Wallace and Grommit, were infamous for leaving fingerprints on their clay models. As a tribute to their animators, they've even included the prints in their newest branding id!


But what if you need to create a video that needs realistic movements? Although uncommon, it's sometimes necessary, especially if you combine real-life footage with stop motion imagery.


If you match up a stop motion sequence with regular footage, you might end up with something like this sequence from Robocop:

Although the animation was done skillfully for the clip you see above, it's still quite apparent that the robot is fake, which significantly diminishes the sense of realism in the movie.

To create realistic movements, you'll have to minimize, or even eliminate, those jitters, no matter how subtle they may be. Of course, you can always try to animate at 24 frames per second for smoother results. But even then, it won't entirely eliminate the natural jitter caused by the stop motion animation technique.


If you want to create super smooth stop motion, you can try video frame interpolation in post-production, and we'll show you how.

What is Video Frame Interpolation?


As discussed in this article, frame rate affects how jittery or smooth your animation will be. The most common frame rate for stop motion animation is 12 and 24 fps, with 24 offering the smoothest results.


Video frame interpolation is a fancy name for adding extra frames to make a video sequence appear smoother.


Below you can see the difference between the original Robocop and the version processed using video frame interpolation.

If you animated at 12 frames-per-second but want a smoother result, video frame interpolation can turn that into 24, 48, 96, or 120 frames-per-second.


What are the most common video frame interpolation apps out there?


Adobe Premiere and After Effects already have built-in video frame interpolation features. The first is Optical Flow, which we mentioned in this article, and the second is a third-party plugin called Twixtor.

However, it's also worth noting that these tools' ability to smoothen animation is quite limited. Sometimes, they don't work as well as dedicated video frame interpolation apps.


We think it's sometimes better to use a dedicated video frame interpolation apps instead. Let's check out some of them below:

Dain App: Dain stands for Depth-Aware Video Frame Interpolation. It's considered by many to be one of the best VFI apps out there, especially since it's free to use. Unfortunately, it only works with Nvidia GPUs (check your computer if it uses Nvidia or AMD GPU!).

Smooth Video Project: Do you ever notice why movies shot at 24 frames per second look so smooth on your television? That's because your smart TV uses video frame interpolation technology. And that's precisely what the same technology SVP app uses, except this time, it applies video frame interpolation on your computer in real-time. It works as well, if not better, as the Dain App, but you'll have to pay for the service.

Flowframes: In many ways, this app is better than Dain App since it's free and works with both Nvidia and AMD (which we have on our computer). It also has the same features as the first two, including letting you choose various frame rates.

How do you use video frame interpolation apps?


For this article, we'll be using Flowframes since it's compatible with most computers and it's free. But for the most part, every VFI apps out there work the same and have similar features.


Step 1: Download FlowFrames. Make sure you choose the Mac version if you have an Apple computer and Windows if you have a PC.

Step 2: Once you open the app, drag the video you want to edit into the dialog box. FlowFrames will automatically detect the properties of the video, such as the clip length and frame rate.

Step 3: Click the dropdown menu next to Interpolation AI and choose your preferred AI interpolation network. To keep it simple for you, select the one that's compatible with your GPU. In our case, we used RIFE (NCNN). But later on, feel free to try the other options as they may yield better results in some cases.

Step 4: Next to OUTPUT FPS and Speed, choose a value between x2 and x8 which refers to the number of frames you want to add. In our experience, it's best not to go beyond x4 because otherwise, you'll start seeing warping and ghosting in the video. Once the program has to start adding more artificial frames than actual ones, you'll end up with many issues.

Step 5: Next to Output Mode, select the video file type you want to use. To ensure your clip is compatible with all computers, it's best to choose MP4 (h264, h265, AV1).

Step 6: Once you finish changing the settings, click the Interpolate button to start the video frame interpolation process.

As you can see, video frame interpolation is relatively easy. All you have to do is tweak the settings and press Interpolate.

The issue with video frame interpolation is that it takes some time to process. For instance, the 5-second video we tested took 18 minutes to finish.


But once the app finishes processing the video, you can see how different the new clip is from the original one as far as smoothness is concerned.

Now let's look at a few comparisons of animated clips using Flowframes.


Original (30fps)


Interpolated (60fps)

Do you see any difference at all? It's subtle, but Flowframes has made everything move like real things, right?

 

Video frame interpolation is a relatively new technology. And although it's helpful in some situations, it's not a substitute for lazy animation. If your stop motion looks too jerky, it will still look jerky even after interpolating it.

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Nonetheless, this technology is still helpful if you need to convert your 12 to 24-frame-per-second animations to higher frame rates. After all, even the best animator can't physically animate more than 30-frames-per-second.