Time a race from a video you already filmed: gun in the audio, crossings at the line
Race Replay quick start
Load a race video filmed from the finish area (a side-on view of the line works best). It stays on this phone.
Find the start: tap Scan audio for the gun and pick the right spike (tap one to jump there and check), or scrub to the flash/smoke frame and tap Set start here. If the camera was far from the starter, enter that distance; sound is slow (about 3 m every 1/100 s) and StatLap corrects for it.
The red line finds the finish line by itself (brightest stripe in view); drag it if it guessed wrong, then tap ▶ Scan for crossings. It watches the whole video, stamps a time on every crossing, and lists the heat in finish order. Runners small in the frame? Set sensitivity to High.
Review: tap any crossing to jump to that exact frame; assign lanes, delete strays, or pause anywhere and + add a crossing the scanner missed (tight packs blur together; that's normal, fix them here).
Reaction time: jump to the gun, step to the athlete's first movement, mark it: block reaction to the thousandth, sound-delay corrected.
Copy the results when it looks right.
This is an add-on for footage you already have; the live two-phone system is still the main way to time a meet.
Load the race video, then drag the red line onto the finish line
Step 1: when did the gun go?
start not set
Reaction time (optional)
Jump to the gun, then step frame ⟩ by frame until the athlete first moves, then mark it. Rulebook line: under 0.100 s is a false start.
no reaction marks yet
Step 2: scan for crossings
Auto-time follows each athlete's body instead of watching one strip of pixels, and slides the finish line along as the camera drifts, so a braced-but-wobbly phone still works. The finish line does have to be in shot when they cross it: if the camera swings away down the track, nothing can time it.