ApexCut

Your best corners, already found.

Your helmet camera writes down how the bike moved, thirty times a second, in every recording. ApexCut reads it, finds the corners, the braking and the hard acceleration, and hands you a movie of the good bits, on your own computer, without uploading anything.

Download · Website · Documentation

What it does

• Finds the good bits by itself. Lean, sustained turning, braking and acceleration are scored from the camera's own motion track. No video is decoded, so a 22 minute ride is scanned in about a second.
• Puts them on a timeline you can edit. Trim an edge, join a chain of corners into one sweep, leave one out, star the best, add your own. Undo and redo everywhere.
• Makes the movie. Widescreen, vertical, 4:3 or the square as recorded, with crossfades, colour looks, music, a telemetry overlay and one button.
• Keeps the bits you point at. Two fingers held up to the camera while riding marks that spot; ApexCut finds the gesture and keeps the ten seconds before it.
• Lets the picture vote, if you want. Tunnels, fast light changes, low evening sun and busy roads can add moments the sensor cannot see, and each one says why it was picked.
• Hands it to your phone. “Send to my phone” serves the finished movie over your own Wi-Fi behind a QR code. Nothing is uploaded, and the link dies after half an hour.
• Sums up the day. A ride card with your sharpest lean, hardest braking, corner count and minutes of real riding, straight to the clipboard.

How it works

1. Point it at a card or a folder. Recordings are paired with the small proxy the camera wrote next to them (.LRF on DJI, .LRV on GoPro) and grouped by riding day.
2. The motion track is read, not the pixels. djmd (DJI) or gpmd/GPMF (GoPro) is copied out and scored; GoPro's accelerometer and gyroscope are fused into an attitude first.
3. You edit and export. The parts land on the timeline; the export crops at full resolution and never scales anything.

Cameras

Camera	What it gives	Notes
DJI Osmo Action	30 Hz attitude quaternion + accelerometer	Read straight out. See docs/dji-metadata.md
GoPro Hero5 and newer	GPMF accelerometer + gyroscope (and CORI on Hero8+)	Fused into an attitude; within a few degrees of the camera's own. See docs/gopro-metadata.md
Anything else	none	Says so plainly; you can still cut by hand

What comes out

Rule	What it means
Resolution	Never scaled: a format crops the recording at full resolution (3840 × 2160, 2160 × 3840, …)
Colour depth	10-bit stays 10-bit, through the colour work and the encode
Square format	Stream copy: the exported parts are the original bytes, cut at the nearest keyframe
Everything else	HEVC at CQ 18 on NVENC / QuickSync / AMF, libx265 fallback, bitrate cap scaled by kept pixels
Sound	The ride's own sound, music under it, and an optional −14 LUFS pass
Your files	Read-only. Movies land in a folder you choose

Install

Grab the installer or the portable build from the latest release. Windows 10 or 11, 64-bit. The installer keeps itself up to date; the portable build leaves nothing behind.

Windows will warn about an unknown publisher, because the builds are not signed with a paid certificate.

Documentation

• How to use it: adding rides, the timeline, colours, music, exporting, sharing, shortcuts, troubleshooting.
• Scoring: what counts as a corner, and every threshold behind it.
• Gestures: how the two-finger mark is found, and how well it works.
• Architecture · Design: how the app is put together.

Building from source

Node 22 (.nvmrc) and npm. ffmpeg and ffprobe come from npm.

npm install
npm run dev            # Electron + Vite with hot reload
npm run check          # lint + typecheck + unit tests
npm run test:e2e       # builds, then drives the real app with Playwright
npm run build:win      # installer + portable build in dist/

End-to-end tests never run in CI: they are the gate before a release is built on a real machine (npm run check:pre-release, which npm run build:win depends on).

src/core is pure TypeScript (parsing, IMU maths, scoring, framing, the gesture detector) and is unit-tested against fixtures, including the metadata of GoPro's own sample recordings and a parity fixture from the Python prototype this was ported from.

Command line

• ApexCut --add=<file-or-folder> adds videos and scans them on startup.

Releasing

Tag vX.Y.Z on main. GitHub Actions builds the installer and the portable build, and publishes a release with the auto-update feed.

Licence

MIT © Darrell van Swinderen