Video Frame Interpolation, Free and Online

Video frame interpolation is the process of creating brand-new frames that sit between the frames a camera actually recorded. Instead of simply repeating each frame to reach a higher frame rate, an interpolator studies how things move from one frame to the next and draws an estimate of what the in-between moment would have looked like. SmoothMotion.video does this in your browser with no account: upload a clip, pick 30, 60 or 120 FPS, and download a smoother MP4 when processing finishes.

What frame interpolation actually does

Every video is a sequence of still images shown quickly enough that your brain reads them as motion. A 24 or 30 FPS clip shows relatively few images per second, so fast pans, moving subjects and scrolling screen recordings can look stepped or juddery, especially on modern displays that refresh 60 times a second or more.

Frame interpolation raises the frame rate by synthesising the missing images. For a 30 FPS clip converted to 60 FPS, one new frame is created between each original pair. For 120 FPS, three new frames are created between each pair. The original frames are kept; the new ones fill the gaps.

There are three broad ways to fill those gaps:

SmoothMotion.video uses the third approach. If you want to understand the theory in more depth, read our explainer on how motion interpolation works.

How SmoothMotion.video interpolates your video

The service uses motion-compensated interpolation configured to favour quality over speed. In plain terms, that means:

• Motion-compensated interpolation – movement is estimated and followed, rather than frames being blended or duplicated.
• Bidirectional motion search – motion is searched both forwards and backwards between frames, which gives more reliable motion vectors.
• Predictive block-based motion estimation – an efficient search finds where each block of the image moved, testing the most likely positions first.
• 16-pixel blocks that can be subdivided – the picture is split into blocks that are broken into smaller ones where the motion is more complicated, such as around the edges of moving objects.
• Overlapped block motion compensation – blocks are blended at their edges to reduce visible blockiness.

For a fuller explanation of each of these stages, read our guide to what motion interpolation is.

Using the tool

1. Upload your video. MP4, MOV, MKV, AVI, WebM and M4V are accepted, up to 500 MB, 5 minutes and 1920×1080.
2. Choose a frame rate. 60 FPS is the default and the best fit for most screens. 30 FPS suits very low frame rate sources, and 120 FPS is aimed at high-refresh displays.
3. Wait while it processes. Each file is checked to confirm it contains a valid video stream, then queued and processed in the background. You will see live progress and a thumbnail that refreshes periodically, taken from the actual interpolated output, so you can judge the result before it finishes.
4. Preview and download. Watch the result in your browser, then download it as an MP4 named like holiday_smoothmotion_60fps.mp4.

The output keeps your original dimensions and audio, plays at the same speed as the source, and is encoded as H.264 with AAC audio in yuv420p with faststart enabled, so it plays almost everywhere and starts streaming quickly. For the step-by-step technical pipeline, see how SmoothMotion.video works.

Which frame rate should you choose?

• 60 FPS is the sweet spot for most uses: it matches the refresh rate of most monitors, laptops and phones and is widely supported for online playback. Our guide to converting video to 60 FPS covers this in detail.
• 120 FPS only makes a visible difference on 120 Hz or faster displays and takes noticeably longer to process. Read when 120 FPS is worth it before choosing it.
• 30 FPS is useful for lifting very low frame rate footage, such as 10–15 FPS screen captures or old webcam recordings, to a standard rate.

Not sure about the trade-offs? Compare 30 FPS vs 60 FPS and 60 FPS vs 120 FPS.

What frame interpolation can and cannot do

Motion-compensated interpolation is good at making steady, predictable motion look fluid: camera pans, tracking shots, walking subjects, scrolling text in screen recordings and smooth gameplay footage. It is honest to say it has limits:

• Fast or erratic motion can produce warping or ghosting where the motion search cannot find a good match.
• Occlusions – objects passing in front of one another – leave areas that were hidden in one frame and visible in the next. The interpolator has to guess, and the guess is sometimes visible as smearing at edges.
• Scene cuts can generate a muddled transition frame if a cut is not detected cleanly.
• Repeated patterns such as fences, grilles or striped shirts can confuse motion estimation.
• Text overlays and on-screen graphics that stay still while the background moves may wobble slightly.
• It cannot add real detail. Interpolation creates in-between positions of what is already there; it does not sharpen, upscale or recover information that was never captured.
• Animation with held frames (for example anime drawn "on twos" or "on threes") may move unevenly, because the identical frames have nothing to interpolate between.
• Film and drama can take on the so-called "soap-opera effect", where cinematic 24 FPS footage starts to look like live television. Some people like this; many do not.

If your footage is mostly smooth motion, you will usually be pleased with the result. If it is dominated by quick cuts and chaotic action, try a short section first.

Processing time

Motion-compensated interpolation is computationally heavy and runs on the CPU. Processing can take longer than the duration of your video, and 120 FPS output or 1080p sources take longer than 60 FPS or smaller resolutions. Jobs run in the background, so you can leave the page open and watch the progress bar and preview thumbnail update.

Your videos stay private

There is no sign-up. An anonymous, HTTP-only cookie links your browser to your jobs, and only you can access your videos. Uploaded and processed media is deleted automatically 30 minutes after processing finishes, and you can cancel a job at any time to delete its media immediately. We do not sell your data. Read the privacy policy for the details.

Ready to try it? Upload a clip using the tool above, or head back to the SmoothMotion.video home page.