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site scripts grade
1 folder · 7 files
ui
color.mjs
color.test.mjs
make_luts.py
media.mjs
README.md
server.mjs
server.test.mjs
README.md

Grade #

A local app for grading camera footage in bulk before it goes into OpenFilm: pick a look, set exposure, white balance, tint, contrast and saturation across many clips at once, watch it live, and export graded copies when it looks right.

bun run grade          # http://127.0.0.1:4777, opens in the browser

Where clips come from #

Clips from (top bar) lists two kinds of folder:

  • Pocket 4P: the camera's card while it's plugged in (/Volumes/Pocket4P/DCIM, GRADE_CAMERA), one folder per shoot day, read from the date in each DJI file name. Clips stay on the card: nothing is copied off it, and nothing is written to it. Thumbnails come from the still each DJI file carries; a clip's preview is made from the card when you select it.
  • On this Mac: any <root>/<folder>/originals/ with video in it, for clips that aren't on the camera.

Each folder shows how many of its clips have a graded copy, and the clip list can show only graded or ungraded clips.

What the app writes #

~/Movies/Pocket4P/                  GRADE_ROOT
  luts/                             GRADE_LUTS: base looks (below)
  2026-11-08/                       a shoot day (or a Mac folder's name)
    grades.json                     each clip's grade, saved as you work
    graded/DJI_…_0234_D.mp4         the export: 8-bit H.264 BT.709, near lossless, sound copied
    graded/DJI_…_0234_D.grade.json  what was applied: source, base, grade, key, LUT, camera white balance
    graded/luts/DJI_…_0234_D.cube   the exact LUT the export used
    .grade/                         the app's cache: preview proxies, thumbnails, probed metadata

A camera day and a Mac folder with the same name share this folder, so a clip graded off the card and the same clip copied to the Mac share one grade and one export. A graded file put in graded/ by hand counts as graded too.

Grading #

  • Look: the base look for the clip's camera profile, read from its own metadata tag. D-Log2, D-Log and HLG get the ACES conversion (from DJI's curve math, out through ACES 2.0 SDR Rec.709); D-Log2 also gets the twelve P4P looks. Rec.709 clips are graded as shot.
  • Exposure in stops, Temperature in Kelvin (as if the camera had been set to it; it starts at the camera's own), Tint (+ magenta, − green), Contrast around 18% grey, Saturation. All of it happens in scene linear light before the look.
  • Select several clips (⌘-click, shift-click, Select all) and a change sets that control on all of them. Copy grade / Paste copies a whole grade.
  • Split and Original compare against the flat original; hold B to flash it. Space plays, ↑ ↓ change clip.
  • Full quality plays the original itself at full resolution (streamed off the card) instead of the 1280 px preview copy, to judge focus and detail; colour is the same either way. It is still 8-bit on screen, because Chrome hands video to WebGL at 8 bits even from a 10-bit file, so judge banding on an export. HLG clips keep the preview copy. Full screen (or F) gives the viewer and its transport the whole screen.
  • Export this clip / Export N selected bakes the selection; Re-export N changed bakes every graded clip whose grade moved since its export. Exports come from the 10-bit originals (off the card, for a camera day) at 16-bit precision, not from the preview. A camera day can't export while the camera is unplugged. Exporting more than ten clips at once asks for a second click; Stop exporting (top bar, while anything exports) drops the queue and stops the clip in progress, which leaves its previous export, LUT and record as they were.

Base looks (luts/) #

File Made by
dlog2-to-rec709-aces2.cube, dlog-…, hlg-… uv run --with opencolorio --with numpy scripts/grade/make_luts.py ~/Movies/Pocket4P/luts
p4p/P4P_01_Neutral_size65.cube … P4P_12_Punch_… Codebater/pocket4-luts (CC BY 4.0), D-Log2 only
custom/<dlog2|dlog|hlg|rec709>/*.cube your own; each shows up as a look for that profile

Every base takes the profile's own code values, read as limited range (the default; the P4P README's advice to read full range lifts blacks).

How the preview stays honest #

color.mjs is shared by the browser and the export: a clip's grade becomes one LUT built by the same function in both, sampled live on the GPU over a small proxy of the clip's own code values, and baked by ffmpeg from the original. On startup the browser decodes a grey ramp encoded like the proxies and compares it with ffmpeg; a decoder that lands more than 1.5 levels off gets corrected. node scripts/check-grade.mjs (not in CI; it needs WebGL; pass CHROMIUM_PATH and optionally SCREENSHOT_DIR) grades a synthetic clip, exports it, and checks the export against the preview: mean 0.8 of 255, 95% within 2.4.

Into OpenFilm #

Edit with the files in ~/Movies/Pocket4P/<day>/graded/: the originals may only exist on the camera. Each .grade.json says what was applied; a clip is current when its key matches gradeKey(resolveGrade(grades.json's entry)), which the app shows as "graded" and otherwise as "changed since export". Regrading and exporting again replaces the file under the same name, so trims and captions in a film stay valid.