12 drawings / s → 60 fps
Anime drawn on twos or threes: drop the repeats, then fill the gaps
A 24fps anime file often holds each drawing for two or three frames, so it carries only 12 or 8 different drawings per second. Ordinary interpolation treats a repeated drawing as "no motion", and the result stops and jumps. With Remove duplicate frames turned on, FrameSmoother skips the repeats, places each drawing at the moment it first appears, and generates the frames between drawings at the frame rate you choose, on the iPhone.
01Frame by frame
Three drawings, two ways to fill them
The top row is a 24fps file animated on twos: drawings A, B and C, each shown twice. The two rows below are 60fps results over the same span. The dot is where a moving character sits.
In the file: 24fps on twos, A A B B C
Interpolated as it is: still, move, still, move
With Remove duplicate frames: an equal step every frame
drawing from the file (outlined)same picture, no motiongenerated frame
This is a diagram, not app output. Positions are idealised; the point is where the motion happens.
02In numbers
Drawings per second, before and after
| Animation in a 24fps file | drawings / s | between drawings |
|---|---|---|
| On ones | 24 | 41.7 ms |
| On twos | 12 | 83.3 ms |
| On threes | 8 | 125 ms |
| FrameSmoother, 60fps target | 60 | 16.7 ms |
What counts as a repeat
| Check | value |
|---|---|
| Brightness sampled at | 256 × 144 points |
| Every 16 × 16-point window (overlapping by half) may have at most this many points that changed by more than 24 of 255 steps | 3 |
| Average change over the whole frame, at most | 1.5 steps |
| Repeats are dropped only within this time of the last kept frame | 3/24 s (125 ms) |
Both conditions have to hold, so a small change such as a mouth flap or a blink keeps the frame, and a fade is not mistaken for a repeat. A still that lasts longer than 125 ms stays still instead of turning into a slow glide toward the next drawing. The length of the video does not change, and the sound is kept.
03On the iPhone
Turning it on in FrameSmoother
The Photos app on iPhone has no setting for removing repeated frames or generating new ones. In FrameSmoother, removing them is one switch.
- Home
Tap Select Video and pick the clip.
- Interpolation Setup › Output Frame Rate
Keep Target fps and choose 60fps.
- Anime
Turn on Remove duplicate frames. The note reads: "For anime drawn on twos or threes. Repeated frames are skipped so the motion between drawings becomes smooth."
- top right
Tap Add to Queue. The Queue opens.
- Queue
When the row says Completed, tap it and step one frame at a time across a drawing change to check the result. Back in the queue, save it with the download-arrow button on the row, or share it with the share button.
04More comparisons