Formats and delivery

• Compose each format as its own stage (own layout and camera keys). Never centre-crop the master.
• Muted autoplay shows the opening seconds instead of the thumbnail: frame 0 must already carry the message (title card), and burned-in captions matter more than voice for feed formats.

Subtitles

• Optional burned-in subtitles: bottom, 30 px, 66 % black box, 0.12 s fades, the line's text from script.json (de etc.), shown from line start to line end + 0.25 s.
• Always also deliver .srt files (node tools/srt.mjs), one per language.
• No em or en dashes as separators in subtitle text; use a comma or a colon.

Files

• out/<Name>_<VO-lang>_1080p60.mp4, out/<Name>_<VO-lang>_<SUB-lang>-subs_1080p60.mp4, out/<Name>_<lang>.srt.
• H.264 high, CRF 15, yuv420p, AAC 256 kb/s, +faststart.
• Keep a poster frame PNG (the end card or the hook) for thumbnails: node ~/.claude/skills/motion-review/tools/inspect.mjs poster <mp4> <t> takes it from the encoded file.
• For social posts, write a short post text that adds what the video can't (context, a link), never the full script again.

Subtitle chunking on cut audio

Caption pages that split on natural pauses fail once audio is cut or concatenated: the pauses vanish and one run put 188 words on a single page for about 2 seconds. Chunk by maximum words (about 3 to 6), maximum on-screen time and sentence boundary, never by pause alone, and test with a deliberately pause-free input. Our line-by-line Kokoro clips sidestep this; it matters when captions are generated from joined or trimmed voice. Evidence: described by the author, not shown (F-C13).

Web-embed delivery checklist

For a loop or hero video embedded on a web page:

• [ ] H.264 High, yuv420p, -movflags +faststart.
• [ ] muted playsinline autoplay loop and preload="metadata".
• [ ] Served with byte-range support.
• [ ] New filename on every re-export so browsers forget a cached failure.
• [ ] -tune grain only if dark gradients band.
• [ ] Size budget checked in the network panel (a short loop can be under 1 MB).
• [ ] Poster image set.

Why: a first-hand 4-hour debug of a clip that played in one browser and showed black in another. We replaced the author's diagnosis (a profile claim we could not confirm) with the standard causes: pixel format, faststart and range requests (F-C12).