Captions From Transcript
Captions are not optional polish - they are accessibility, they hold viewers watching muted, and for tutorials they reinforce exact UI terms. This skill produces a clean, accurately timed caption file. Styling and burn-in happen downstream.
Source the most accurate text first
Accuracy comes from where you start:
- If a narration script exists, use it as ground truth. It is already correct on technical terms and UI labels. Align it to the audio rather than re-transcribing from scratch.
- Otherwise transcribe the audio (Whisper, a platform's auto-caption, or any ASR), then correct it against the video. ASR reliably mangles product names, code, and acronyms - fix every one to match what is on screen exactly.
Never ship raw ASR output. The errors are always in the highest-value words.
Time the cues to speech
- Each cue appears as its line is spoken and clears when it ends - align to speech, not to arbitrary intervals.
- Minimum ~1 second on screen (even for a short cue), maximum ~7 seconds. Split anything longer.
- No gaps mid-sentence; small gaps between sentences are fine and aid readability.
Line and reading rules
- 1-2 lines per cue, never 3.
- ~32-42 characters per line. Past that it crowds the frame and overruns safe areas.
- Reading speed ≤ ~17 characters/second (≈160-180 wpm). If a cue exceeds it, the words flash by - split the cue or extend its duration.
- Break lines at clause boundaries, never mid-phrase. Keep "to the Settings page" together; don't strand "the" alone on a line.
Choose the format
- SRT - universal, index +
HH:MM:SS,mmm --> HH:MM:SS,mmm+ text. Use for upload to most platforms and editors. - WebVTT (.vtt) -
WEBVTTheader,HH:MM:SS.mmmtimestamps, supports positioning/styling cues. Use for HTML5<track>and the web player.
Produce valid, parseable output - correct timestamp punctuation (SRT uses a comma before milliseconds, VTT a period), blank line between cues, no trailing whitespace.
Clean vs verbatim
For tutorials, caption clean: drop filler ("um", "uh", false starts), keep meaning verbatim. Preserve technical terms, code, and UI labels exactly. Only go strict-verbatim if the user explicitly needs it (legal, research, exact-quote contexts).
QA the sync
Spot-check against the actual video at the start, a middle point, and the end - drift accumulates. Confirm cues land on their lines and clear before the next begins. Fix any caption that lingers over the wrong shot.
Hand off
The finished .srt / .vtt feeds social-video-formatter for burn-in and platform styling, or the web player's <track> element directly. Leave color, font, position, and animation to those steps - this skill outputs accurate, well-timed text and nothing more.
Don't
- Don't style, color, position, or burn captions into the frame - that is social-video-formatter.
- Don't animate words word-by-word - that is kinetic-typography.
- Don't ship uncorrected ASR; the mistakes cluster exactly on the terms that matter.
- Don't pack 3 lines or overrun the reading-speed budget to avoid splitting a cue - split it.