Captions From Transcript

Captions From Transcript 是做什麼的？

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) - WEBVTT header, HH:MM:SS.mmm timestamps, 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.