captions

name	captions
description	Add subtitles/captions to a video — burn them into the picture, or export an .srt/.vtt file (for YouTube etc.). Use whenever the user wants captions, subtitles, on-screen text of what's being said, an SRT/VTT file, or accessibility text. Covers auto-transcription, editing for accuracy, styling, and the verbatim-vs-clean gotcha.

Captions & subtitles

Two outputs, one transcription engine (mlx-whisper, same as transcribe):

• Sidecar file (.srt / .vtt) — for YouTube/Vimeo upload, re-editing, or other tools.
• Burned-in — pixels baked into the video (social clips where the player won't show a subtitle track). Rendered via PIL → ffmpeg overlay (mise ffmpeg lacks drawtext).

CRITICAL: use --clean for captions

This is the opposite of filler-removal. Whisper is verbatim by default here (keeps um/uh) because filler-removal needs them. Subtitles do not — viewers don't want "um, uh" on screen. Always pass --clean when transcribing for captions:

uv run video-agent transcribe video.mp4 --clean --srt -o subs.srt

Export a subtitle file (no burn-in)

uv run video-agent transcribe video.mp4 --clean --srt -o subs.srt   # SubRip
uv run video-agent transcribe video.mp4 --clean --vtt -o subs.vtt   # WebVTT

Upload subs.srt alongside the video, or hand-edit it (fix names/typos, retime) and burn that edited file — see below.

Burn captions into the video

# Auto-transcribe and burn in one step (uses --clean transcription internally? NO — pass it)
uv run video-agent captions video.mp4 -o captioned.mp4 --clean

# Best workflow for accuracy: transcribe → hand-edit the .srt → burn the edited file
uv run video-agent transcribe video.mp4 --clean --srt -o subs.srt
#   ...fix typos, proper nouns, retime any off lines in subs.srt...
uv run video-agent captions video.mp4 --srt subs.srt -o captioned.mp4

--srt accepts both .srt and .vtt. When --srt is given, no transcription runs — it just burns the file you pass, so this is also how you re-burn after editing.

Styling

uv run video-agent captions video.mp4 -o out.mp4 --srt subs.srt \
    --size 48 --color yellow --position bottom --no-box

• --size px (default ~5% of frame height) · --color white|yellow|red|black
• --position bottom (default) | top | center
• --no-box removes the semi-transparent legibility box (keep it for busy backgrounds)
• Text auto-wraps to ~90% of frame width, centered.

Gotchas

• Caption count = encode passes? No — one pass. Every segment becomes a full-frame RGBA PNG overlaid with an enable='between(t,…)' gate, all in a single ffmpeg encode. Fine for clips and typical talks. For a very long video (many hundreds of segments) the command line gets large; split the video, caption each part, then concat.
• Timing comes from whisper segment boundaries, which read fine but can be ~0.3s loose. For tight sync, edit the times in the .srt and re-burn with --srt.
• Word-level "karaoke" captions (one or two words popping per beat) aren't built in here. Approximate by transcribing --words, grouping into short segments, and writing your own .srt with tight start/end per group, then captions --srt. For animated per-word pops (eased, scaled), use the optional remotion-graphics skill's KineticCaption — fed the same --words timestamps. Either way the timing is grepped from the --words transcript, never scrubbed.
• Burn on the final-resolution video. If you're also reframing for social (reframe skill), reframe first, then caption — so font size and wrapping match the output frame, not the original.