Matching fps
A PNG sequence has no notion of 'how many seconds long', only an image count. Your editor flips through the images at a set fps, so if that fps differs from the original, the doodles gradually lag behind or run ahead.
How far off does it get?
One minute of 30fps video = 1,800 images. Read at 29.97fps, the last image shows about 0.06 seconds (2 frames) late; read at 24fps, the one-minute clip stretches to 75 seconds. The closer the numbers, the less you notice it at the start and the more it shows toward the end, so always check the end.
Finding the original fps
- When you open a video in the editor, its size and frame count appear at the top, and the fps box on the screen is preset to the original fps.
- The Video check page shows the measured fps (e.g. 29.970) and whether it's variable.
- In your editor, look in the original clip's properties (info) panel.
Numbers that are easy to mix up
| Shown as | Actual value | Typical use |
|---|---|---|
| 23.976 (23.98) | 24000/1001 | Camera footage shot for a film look |
| 24 | Exactly 24 | Cinema cameras, some iPhone Cinematic mode |
| 29.97 | 30000/1001 | Broadcast, and '30p' on many cameras |
| 30 | Exactly 30 ('about 30' on phones) | Phone default |
| 59.94 / 60 | 60000/1001 / 60 | Smooth video, sports |
| 119.88 / 120, 240 | High-speed capture for slow motion |
23.976 and 24, and 29.97 and 30, are different values. On the export screen, pick exactly the same number as the original.
iPhone and Galaxy (variable fps)
Phones record with variable fps, where frame spacing wobbles a little with light and heat. Editors usually conform such video to a fixed fps (e.g. 30) on import, so make the PNG sequence at that fps (the value the editor presets).
- The editor draws doodles at the actual frame times in the video, so the preview and composited mp4 stay accurate with variable fps.
- The PNG sequence uses even spacing, so video with very irregular frame timing (dark scenes, screen recordings, etc.) can be off by a frame or two. For scenes that must be exact, use the composited mp4, or convert the original to a fixed fps in your editor before working.
Slow-motion and high-speed footage
- iPhone and Galaxy slow motion: the file itself is often stored at 120 or 240fps, and only the Photos app plays it slowed down. The file's fps can change depending on how you share or export it, so go by the fps the editor shows when you open it. To use slow motion in your editor, apply exactly the same speed change to the original and the PNG clip.
- Camera S&Q / HFR (in-camera slow motion): even when shot at 120fps, the file is often saved at 24 or 30fps. In that case, match the file fps (24 or 30).
- Higher fps means more images and longer exports (1 minute at 240fps = 14,400 images). A composited mp4 can only be made if the browser's encoder supports that size and fps; if not, the export screen tells you up front.