remotion-qa

Measure the rendered file, never the composition source. A source can't tell you whether a line wrapped, whether a card overflowed into the platform UI, or how long a frame actually sat frozen. A readability check that compares a duration with the value it was computed from can never fail, so it is not a check.

1. Pacing, in both directions

npx remotion-qa pace out/video.mp4 --beats captions.srt

--beats takes .srt, .vtt, or JSON ([{ "start": 0, "end": 2.5, "text": "line one\nline two" }], or { "from", "to" } in frames with fps). If the project has no captions file, write a beats file from the composition's own text and timings.

Read the output correctly:

• A static run is not automatically dead air. A frozen frame while the viewer is still reading is reading time. Dead air is only the part after they've finished. The tool does this subtraction for you when given beats: required = longest_line_chars / 15 + 0.4s per extra line + 1s, counted from when the beat arrives.
• TOO FAST beats are the opposite failure: the text leaves before it can be read sound-off. Both count.
• Footage with a slow push registers as still (a few % zoom over a beat is under a pixel per frame). Only judge runs that sit on a flat graphic ground.
• The tail of an eased entrance reads as still (an ease-out is ~94% done at half its duration). A run starting mid-entrance is part entrance, part hold.

Fix over-holds by pacing, not trimming. Shortening the beat trades dead air for "too fast". Stagger the reveal so a list builds at reading pace (items ~20 frames apart, not 4), then hold only for the last item to settle.

2. Safe zones

npx remotion-qa safezone out/video.mp4 --frames qa-frames/

Reports how far ink reaches into each platform overlay (the caption, buttons, progress bar), in canvas px. Open the saved frames: text in a shaded zone is a defect, decoration there is fine. Bands holding footage aren't judged; say so rather than calling them clear.

Channels: reels-union (default for 9:16, the worst case of IG Reels, FB Reels and YT Shorts), ig-reels, fb-reels, yt-shorts, yt-landscape, feed-square, feed-portrait.

3. Type sizes

npx remotion-qa floors --channel reels-union --font-factor 1.08

Floors are calibrated to a 360pt-wide Android (on-device pt = canvas px / 3 on a 1080 canvas). They are floors, not targets: size each element as large as its layout allows. Lighter faces need a --font-factor (1.08 for Manrope 600/700). In a composition, assertLegible(px, role) throws below the floor.

Bigger type changes line counts, and line counts change reading time, so re-run pacing after any size change.

4. Gate renders

npx remotion-qa render MyComp out/video.mp4 --max 5

Renders, then fails if any static run exceeds --max seconds, moving the file to out/video.failed-pace.mp4 so nothing sits at the path people send from.

Report

Per file: each static run with the text on screen, its required seconds and the dead air; each too-fast beat; each safe-zone intrusion with depth and the frame; any type under its floor. Recommend a fix per finding, preferring a stagger to a trim. Never change copy or timing as part of a sizing fix, or sizes as part of a pacing fix: report what the other pass should pick up.