Frame interpolation

What Is Frame Interpolation? How It Works, the Soap Opera Effect, and the Downsides

Frame interpolation makes motion in a video smoother by creating new frames between the ones that were recorded. It’s behind TV “motion smoothing,” game frame generation, and apps that turn 30fps into 60fps, and it’s also the cause of the soap opera effect many people dislike. This guide explains how it works, why it sometimes looks wrong, and when it’s worth using.

Published October 24, 202614 min read

What is frame interpolation?

A video is a series of still pictures (frames) shown one after another. Frame interpolation takes two neighboring frames, works out what the picture would have looked like at a moment between them, and inserts that new frame.

Insert one new frame in every gap and a 30fps video becomes 60fps. Insert three and it becomes 120fps. In the diagram below, each box is 1/120 of a second.

The duplicated and interpolated versions are both 60fps files. The only difference is what’s in the added frames: a copy of the previous picture, or a new picture of the moment in between. That difference decides everything you see, and it’s why many “60fps converters” change nothing (see how to convert 30fps to 60fps on iPhone).

Isn’t that what animators do?

The idea resembles in-betweening, where animators draw the frames between key poses. The difference is control. An animator designs the timing and shape of every in-between, while frame interpolation guesses them automatically from finished footage, which is why it can flatten an animator’s timing (more on that below).

Frame interpolation vs motion smoothing vs frame generation

You’ll see the same basic idea under several names. They differ mainly in where it runs and whether the result is saved.

Frame interpolation vs frame generation

Frame generation is the gaming version. NVIDIA, for example, says DLSS Frame Generation “boosts performance by using AI to generate frames while maintaining great responsiveness with NVIDIA Reflex.” The goal matches video interpolation, but it happens in real time, on frames that don’t exist until the game draws them.

Source: NVIDIA DLSS (checked October 2026)

Doing it live has a cost: to build a frame between two others, the system needs the next frame first, which adds a little delay. That’s why responsiveness comes up whenever frame generation does. An app that re-renders a video file has no deadline at all, so it can take as long as it needs and save the result.

How frame interpolation works: 4 methods

Anything sold as “frame interpolation” or “frame rate conversion” does one of four things under the hood. The first two don’t estimate motion at all, so strictly speaking they aren’t interpolation.

1. Duplicating frames

The previous frame is copied. The file’s frame rate goes up, but the picture changes as often as before, so motion looks identical. It’s useful for meeting a delivery spec, and it’s why so many 60fps conversions look exactly like the original.

2. Blending frames

Each new frame is a 50/50 mix of its two neighbors. Changes look a little more gradual, but anything that moves appears twice, half-transparent. It’s very fast because no motion is estimated.

3. Optical flow

Optical flow is a map of where every point in the picture moved between two frames. The software estimates that map, shifts (warps) the neighboring frames halfway along it, and combines them into the new frame. Motion-estimation approaches like this have long been used for slow motion in editing software and for TV motion smoothing.

Its weak spot is when there’s nothing to warp. If someone walks in front of a wall, the part of the wall they uncover isn’t in the previous frame at all. Uncovered areas, very fast motion, and repeating patterns are where smearing and warping appear.

4. AI models

A neural network is trained on large amounts of video to predict the middle frame from the frames around it. Because it learns both the motion estimation and how to build the picture, it tends to handle uncovered areas and fine detail more naturally than older methods.

A well-known model is RIFE (Real-Time Intermediate Flow Estimation). Its paper was first posted in 2020 and accepted to ECCV 2022, a major computer vision conference, and RIFE is used in many tools, from free PC software to phone apps. It’s still an estimate, though, and in difficult scenes AI interpolation breaks too.

Source: Huang et al., “Real-Time Intermediate Flow Estimation for Video Frame Interpolation” (arXiv; accepted to ECCV 2022)

The free tool ffmpeg names the first three directly: its motion interpolation filter offers dup, blend, and mci (motion-compensated interpolation) modes (ffmpeg documentation). If you’re deciding between recording at 60fps and interpolating later, recording wins when you can. See 30fps vs 60fps vs 120fps on iPhone.

Smoothing while you watch vs re-rendering a file

Frame interpolation lives in two separate worlds. Keeping them apart explains how you can hate your TV’s motion smoothing and still want interpolation for your own videos.

So the choice depends on the goal. For watching a movie the way it was made, turn live smoothing off. For a clip you want to post or keep, a re-rendered file is the only kind you can share.

How to turn off motion smoothing on your TV

Every TV brand gives motion smoothing its own name, and menus change between model years. These are the names the manufacturers use on their own support pages:

Sources: Samsung, LG, Sony BRAVIA Help Guide (checked October 2026)

If your TV has FILMMAKER MODE, that’s the one-step option. The UHD Alliance’s specification lists “Motion Smoothing/Interpolation: OFF” and says the mode should keep the source frame rate and aspect ratio, so selecting it turns smoothing off.

Source: FILMMAKER MODE, “About” (checked October 2026)

Filmmakers feel strongly about this. In December 2018, Tom Cruise and director Christopher McQuarrie released a video asking viewers to turn motion smoothing off.

Source: /Film, “Tom Cruise Demands You Turn Off Your Motion Smoothing” (December 2018)

Why it looks weird: the soap opera effect and artifacts

The smoothness people enjoy in sports and games feels wrong in movies. Smoothness itself isn’t the problem. The problem is motion that doesn’t match what you expect from that kind of footage, and there are three reasons it happens.

1. The soap opera effect: eyes trained on 24fps

Most movies are filmed at 24 frames per second, as Samsung’s own support page points out. That slightly steppy motion is what we’ve learned to read as “cinematic.”

TV soap operas, on the other hand, were typically shot on cheaper video at a higher frame rate, so their motion looked smoother. When a TV smooths a movie, the movie starts to move like daytime TV, hence the name. Complaints that a film “looks like a home video” or “like behind-the-scenes footage” describe the same effect.

References: Samsung, “Motion smoothing and the soap opera effect on Samsung TVs”; Wikipedia, “Soap opera effect” (checked October 2026)

2. The blur stays, the frames multiply

A camera records movement during each exposure as motion blur. Each 24fps frame is exposed for a relatively long time, so fast action is blurry. Interpolation can’t remove that blur, so you get smeared objects gliding smoothly, a look no real camera produces.

3. Artifacts when the guess is wrong

Every generated frame is a guess. When the guess is wrong you get artifacts, and they show up in predictable places:

Live interpolation has very little time per frame, so it’s harder for it to avoid these. That’s why TV smoothing sometimes flickers around subtitles or warps a runner’s arms and legs.

Why interpolated anime looks off

Anime is one of the hardest cases, and the reason is how it’s made. Much hand-drawn TV animation is delivered at 24fps but drawn “on twos” (each drawing held for 2 frames, so 12 drawings per second) or “on threes” (held for 3 frames, 8 drawings per second). The diagram shows half a second at 24fps.

Combine that with interpolation and several things go wrong:

• Uneven motion. Repeated drawings look like “no motion,” so nothing changes there. New frames appear only at the moment the drawing changes, giving a stop, glide, stop rhythm. Some tools can remove duplicate frames before interpolating.
• Flattened timing. Fast and slow beats in animation are deliberate acting, set by the number and timing of drawings. Filling every gap evens them out.
• Characters and backgrounds out of sync. A background may move every frame while a character changes every third, which confuses the estimate.
• Visible line and color breakup. Clean lines and flat colors make broken lines and smeared edges easier to see than in live action.
• Smears and snaps melt. Animators sometimes jump between shapes on purpose with no in-between. Interpolation forces a blend, and the drawing seems to melt.

The smoothness anime fans praise comes from animators drawing more frames. Interpolated smoothness is a different thing that changes the creators’ timing, so use it knowingly.

Does frame interpolation improve quality? The downsides

No: frame interpolation adds frames, not detail. Blur, noise, compression artifacts, and resolution stay the same. Making a video sharper or higher resolution is a different technology (upscaling or super-resolution).

The other downsides to know about:

• Artifacts can appear with fast motion, overlapping objects, thin lines, text, and scene cuts.
• Movies, dramas, and anime lose their intended look: the 24fps film feel and the animators’ timing.
• Generated frames aren’t a real record. Don’t use them to judge a close call in sports or for precise motion analysis.
• It costs time or delay. Re-rendering takes processing time for every new frame; live smoothing adds a little lag.
• It can’t bring back lost moments. Dropped frames and things the camera never captured stay missing.

When to use frame interpolation, and when not to

Don’t like the look? That’s a fair reaction

If you want to see films the way their makers intended, interpolation can feel like vandalism, and on a TV you can simply switch it off. Your own phone videos are different: they were never meant to look like cinema, and smoother motion often makes them easier to watch. Treat watching movies and fixing your own clips as separate decisions.

Try frame interpolation on your own videos

If the video is on your iPhone, you don’t need a computer. FrameFlo, the app I develop, runs the RIFE model on the iPhone itself and saves a new video that includes the generated frames. Nothing is uploaded, and it works in airplane mode.

The artifacts above can happen in any app, depending on the footage. In FrameFlo you can drag a split slider across the original and the result to check before you save. The free version processes clips up to 10 seconds (or the first 10 seconds of a longer clip) at up to 60fps and saves the result.

• Not sure what you’re starting from? Check your video’s frame rate on iPhone first.
• Step by step: convert 30fps to 60fps on iPhone, or make a normal video slow motion after recording.
• Thinking about 120fps? When converting to 120fps is worth it.
• Comparing apps: how to choose a frame interpolation app for iPhone. On a computer, Flowframes is a popular RIFE-based tool for Windows; this guide covers the alternatives if you don’t use Windows.

FAQ

Written by punimaru, the developer of FrameFlo. App details are based on how the app is actually built. Since this is my own app, I’ve also noted where it isn’t the right tool and what else you can use.