Rendering and checking

raea renders the same tree the viewer gets, so a still from it is the truth about layout: fonts, footage, 3D and text overflow only show up in pixels. raea check then measures what a still can't, such as a word clipped for three frames, a stretch of black or a voice buried under music. This page covers both.

#Stills

Render the frames you want to look at as PNGs:

raea render piece.tsx --at 15,63,144,270 -o stills/      # four frames, as stills/frame-00000.png and on
raea render piece.tsx --frame 120 -o frame-120.png       # one frame, to one file
raea render piece.tsx --alpha -o frames/                 # every frame as a transparent PNG, for another editor

Pick the moments that matter, look at all of them at once, fix everything they show, and look again. A contact sheet of a finished video shows the whole piece in one image:

raea media sheet piece.mp4 -o sheet.png

#Video

raea render piece.tsx -o piece.mp4
raea render piece.tsx --composition wide -o wide.mp4   # one of several compositions in the file

An MP4 from raea is H.264 in yuv420p. On a Mac it is encoded with VideoToolbox (H.264 High, AAC audio); on Linux and Windows with openh264 (H.264 Constrained Baseline, Opus audio).

The output's folder must exist: -o out/piece.mp4 needs out/ already there.

#Quality and bitrate

By default the bitrate follows the size and frame rate: about 20 Mbit/s at 1080p30 and 80 at 4K30.

--quality asks for constant quality: each frame gets the bits it needs, so a flat motion graphic stays small and a busy one stays clean.

Blotchy dark areas come from the encoder, not the composition. Export dark material as PNG frames and encode them with more bits for the darks:

RAEA_READBACK=rgba raea render piece.tsx -o frames/

#A share copy

A raea MP4 is standard but large. For a copy any player and any upload takes, re-encode it with ffmpeg:

ffmpeg -i film.mp4 -c:v libx264 -preset slow -crf 23 -maxrate 2600k -bufsize 5200k -pix_fmt yuv420p -c:a aac -b:a 128k -movflags +faststart film-share.mp4

#The quick check

raea check piece.tsx --quick

The quick check renders three stills of a composition and measures its text: clipped, cramped, inside the safe areas and large enough to read. It takes about a second. Run it after every save. Add --platform tiktok (or reels, shorts) to check against that platform's buttons and captions.

#The full check

Render with a manifest, then check the export:

raea render piece.tsx -o piece.mp4 --manifest render.json
raea check piece.mp4 --manifest render.json --words words.json --platform tiktok -o check.json

The manifest records where every element was on every frame, so the check can say which element a problem belongs to. The full check measures:

• clipped text, text under the platform's buttons, and text over a face
• captions on screen too briefly to read, and caption contrast against the pixels behind them
• frozen stretches and flashing past the safe limit
• cues that miss the word they were tied to (with --words)
• loudness, sound that stops dead, and sound that fights the voice
• blotching in dark areas

Each finding is ranked P0 (broken) to P3 (polish) and comes with its fix. The command exits 1 while any P0 or P1 stands, so a script or an agent can stop on it. -o check.json writes the findings for a later review.

An exception in the composition fails the render itself and names the line: a value that turned into NaN, keyframes out of order, a phrase word() can't find, or a missing prop.

#Loudness

When the composition has a <Mix>, the export comes out at -14 LUFS integrated (within 1) with true peak at or below -1 dBTP, which is what the major platforms play back at.

#Mistakes to avoid

• Judging layout from the code. Text overflow and contrast against footage only show in pixels.
• Checking frame 0 only. Most problems are at cues and joins.
• Calling it done without listening. The voice must stay clear over the music, and every sound should land.
• Rendering a new version over the old one. Render piece-v2.mp4 beside piece.mp4.