After calibration, Smashspeed steps through your clip and tries to find the shuttlecock in each frame, drawing a box around it. Speed comes from how far the center of that box travels between frames, so the boxes being accurate is what makes the number accurate. This screen lets you check and correct them.
AI boxes vs. your edits
Boxes the AI placed on its own are shown in one color; boxes you adjust or add are shown in another, so you can always see what has been changed by hand. You step through the clip frame by frame with the slider to inspect each one.
Fixing a box
There are two adjustment modes:
- Move repositions the box without changing its size.
- Resize keeps the box centered but makes it larger or smaller.
Tap an arrow once for a small nudge, or hold it down to move faster. Aim for a tight box around just the shuttle — a loose box shifts the center point and skews the speed. If the AI missed a frame entirely, an Add box option lets you create one.
Filling gaps with interpolation
If the AI loses the shuttle for a few frames (motion blur, glare, or it briefly leaves the frame), you get a gap. Interpolationfills those gaps by smoothly estimating the shuttle’s position between the frames where it was found. When the app detects gaps it recommends this, and using it generally gives a steadier, more reliable speed.
Undo, redo, and zoom
Every change is saved, so you can undo and redo freely while you work. You can also pinch to zoom and pan the video to place boxes precisely; zooming only changes your view and never affects the measurement.
Why the speed jumps between frames
It is normal for the per-frame speed to vary — each frame catches the shuttle at a slightly different point. The figure that matters is the peak speed across the smash. Cleaner boxes and a higher frame rate reduce the jumpiness.