Video Captioning

Mission

Create a readable, reviewable caption layer for an approved video. Preserve the original cut and distinguish machine transcription, human corrections, translated text, burned-in captions, and sidecar files.

Use Video Assembly when captions are one part of a final timeline. Use this skill when caption accuracy, accessibility, or platform variants is the main deliverable.

Required inputs

• approved video parent and measured duration;
• source language, speaker names, terminology, numbers, and exact copy;
• caption type: transcript, subtitles, translated subtitles, or accessibility captions with sound cues;
• target format, ratio, safe area, line length, reading speed, style, and burn-in versus sidecar output;
• music/dialogue mix and whether non-speech audio cues are required; and
• rights, reviewer, disclosure, and definition of done.

Never silently rewrite uncertain speech, product claims, names, or legal copy. Mark uncertain spans and request a source transcript or human correction.

Pipeline

1. Freeze the parent video and record duration, frame rate, language, speakers, and source rights. Do not caption an unapproved or changing cut.
2. Generate or ingest a transcript using media.caption_video or an approved host-local path. Retain timestamps and confidence/uncertainty when exposed.
3. Normalize punctuation and line breaks without altering meaning. Apply approved terminology, speaker labels, sound cues, and translation rules.
4. Check timing against speech, shot changes, music, and visual text. Keep captions within safe areas and readable at the target size; test high-motion backgrounds and mobile framing.
5. Render a captioned draft or return a sidecar/timeline handoff. Poll the job and record the exact output. Do not assume caption generation burns text into a video or preserves every styling field.
6. Review the complete output with video QA: spelling, names, numbers, claims, timing, contrast, overlap, omissions, reading speed, export compatibility, and disclosure.

Check MODELS.md and muapi-video-tools.md for the current caption operation, input shape, and output behavior.

Output contract

Return parent ID, transcript/caption version, source language, confidence or uncertainty list, corrected terms, caption format/style, model/endpoint, prediction ID, output URL or sidecar, QA findings, unresolved spans, and the next reviewer action. Save permitted text and receipt artifacts under .video/ using reports-and-receipts.md.

Captioning is draft-only. It does not certify accessibility or platform compliance unless a current rule set and human review support that claim.