Slow Motion Video Maker
Turn a moment in your video into smooth slow motion. Pick the part to slow down, choose a speed from 0.1× to 0.75×, and let frame interpolation or frame blending create the missing in-between frames. The audio is stretched without the chipmunk-in-reverse pitch drop, or muted.
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Slow motion settings
SpeedChoose a video. The demo above shows the selected speed on a bouncing ball.
How to use the Slow Motion Video Maker
- Choose a video. Short clips with clear motion (sports, pets, splashes, dance moves) work best.
- Mark the slow part. Play the video and press “Set to playhead” for the start and end, or click Whole video.
- Pick a speed. 0.5× doubles the length of the slow part; 0.25× makes it four times longer.
- Choose smoothing and audio. Frame blending is quick; motion interpolation is the smoothest but slow. Keep the audio pitch-corrected or mute the slow part.
- Create and download. Click Create slow motion video, wait for processing to finish, then download the file.
How long does the slow part become?
New length = part length ÷ speed. The real frames per second of motion left in the slow part is source fps × speed; everything above that is generated by blending or interpolation.
| Speed | 1 s of video becomes | Real frames per second (30 fps source) | Real frames per second (60 fps source) | Good for |
|---|---|---|---|---|
| 0.75× | 1.33 s | 22.5 | 45 | Subtle, cinematic slowdown |
| 0.5× | 2 s | 15 | 30 | Sports replays, dance, B-roll |
| 0.25× | 4 s | 7.5 | 15 | Jumps, tricks, water splashes |
| 0.1× | 10 s | 3 | 6 | Dramatic effect; needs interpolation or high-fps footage |
Frame interpolation vs. blending vs. duplication
| Method | ffmpeg filter | Look | Speed |
|---|---|---|---|
| Motion interpolation | minterpolate=mi_mode=mci | New in-between frames, very fluid; can warp edges on fast or complex motion | Slow |
| Frame blending | framerate | Smooth with soft ghosting between positions | Fast |
| Frame duplication | fps | Sharp frames that stutter at low speeds | Fastest |
Tips for better slow motion
- Keep the slow part short (1 to 4 seconds). Slow motion is most effective on a single peak moment: the jump, the hit, the splash.
- Avoid shaky footage for interpolation: camera shake makes motion estimation guess wrong. A tripod or stabilised clip gives much cleaner frames.
- If interpolation shows warping around fast-moving edges, switch to frame blending or use a less extreme speed.
- For a whole clip at one speed without interpolation, the Video Speed Changer is quicker.
Frequently asked questions
How does slow motion from normal video work?
A 30 fps clip slowed to 0.25× has only 7.5 real frames per second of playback. To keep motion smooth, the missing frames are created: motion interpolation estimates how pixels move and draws new in-between frames, frame blending mixes neighbouring frames, and duplication simply repeats them.
Which smoothing method should I choose?
Use frame blending for most clips: it is fast and looks smooth at 0.5× and 0.75×. Choose motion interpolation for short, showcase moments at 0.25× or slower, when you can wait. Duplication keeps every frame sharp but looks choppy at low speeds.
Why is motion interpolation so slow?
Motion estimation analyses blocks of pixels in every frame pair and runs on one CPU core inside the browser. Expect roughly a few frames per second, so a 3-second clip at 0.25× and 30 fps (360 output frames) can take a few minutes. Desktop ffmpeg with the copied command is faster.
Will the audio sound deep and slow?
No, by default the audio is time-stretched with ffmpeg's atempo filter, which keeps the original pitch. Speech becomes slow but not deeper. Very low speeds (0.1× to 0.25×) can sound smeared, so muting the slow part is often the better choice.
What is the best way to film for slow motion?
Record at a high frame rate (60, 120 or 240 fps) if your camera allows it; real frames always look better than generated ones. Bright light gives faster shutter speeds and less motion blur, which also helps interpolation.
Is my video uploaded to a server?
No. The video is processed locally with ffmpeg compiled to WebAssembly, downloaded once (about 31 MB). If ffmpeg cannot load, the tool records the slow motion in real time using repeated frames.
How long will the output be?
Only the slow part gets longer: its length is divided by the speed. A 10-second video with a 2-second part at 0.25× becomes 8 + 2 ÷ 0.25 = 16 seconds.
Are all the tools on FreeToolCabin tested for quality and accuracy?
Yes! Every tool on our site undergoes automated Q/A testing in real browser environments to ensure high precision, correct output, and zero errors. If you happen to spot a bug or have a suggestion, please contact us at [email protected] and our team will review it right away.