Slowing a normal video down usually shows each frame for longer, and movement starts to stutter. Smooth slow motion calculates the missing frames instead: a clip slowed down 4 times gets three new frames between every pair of original ones, so it still plays at its own frame rate and the motion stays fluid.
How to make smooth slow motion
- Upload a clip (MP4, MOV, MKV, WebM, AVI, WMV, MPEG, TS and more; up to 1 GB) or an animated GIF.
- Smooth slow motion, 4 times slower and Motion interpolation are already chosen. 2 and 8 times slower are there too.
- Start, and download the slow-motion video.
What you get
- A longer clip at the original frame rate: 5 seconds slowed down 4 times last 20 seconds, still at 30 fps if the original was 30 fps (up to 60 fps).
- No sound: slowed-down speech and music are rarely wanted, so the sound is left out. To slow a video down with its sound, use Change the speed in Video Effects.
- Format: MP4, MOV, MKV and WebM stay in their format; other formats become MP4, re-encoded at high quality. Upright phone videos stay upright.
- GIFs give a slow-motion GIF with the loop setting and transparency kept.
Getting a good result
- Choose clips with clear, steady motion: a jump, a splash, a ball in flight, a slow pan. Very fast motion, motion blur, fine patterns and objects crossing each other can show warping or smearing, because their movement can't be estimated exactly.
- Start from the most frames you have: a clip recorded at 60 fps slows down better than the same scene at 30 fps, because less has to be calculated.
- Keep it short: slow motion is for moments. Cut the moment out first with the video trimmer.
- If warping shows, try Frame blending: it mixes neighbouring frames, never warps, and gives a softer, dreamier slow motion.
Limits
Motion interpolation is slow: pictures larger than 720p are made smaller to 720p first, and the work is counted on the calculated frames. In one job, about 1 minute of 720p at 30 fps can be slowed down 2 times, about 30 seconds 4 times, and about 15 seconds 8 times. Frame blending allows about 20 times as much, up to 1080p.
More about what this tool reads and writes: Frame Rate Converter.