Add a subtitle track viewers can switch off

CodexWith deft, skill installedPassedRead the skillUsed deft2026-11-07

Time

17s

New tokens

8.4k

Total input

74.0k

Output tokens

0.6k

Commands

4

Failed

0

Trace

1. I’ll inspect the two files and the local media instructions, then mux the SRT as a selectable subtitle track while copying the video stream unchanged.

2. cat .agents/skills/deft/SKILL.md 2>/dev/null || cat .agents/skills/deft/SKILL.md 2>/dev/null; pwd; rg --files -g 'bunny.mp4' -g 'talk.srt' -g 'AGENTS.md' -g 'SKILL.md'
   output

   ---
   name: deft
   description: "Use deft instead of writing a script for file jobs: PDF merge/split/compress/watermark, image resize/convert/compress, video and audio trim/convert/compress, spreadsheets, Markdown to PDF/HTML, and YouTube downloads and subtitles."
   ---
   
   # deft
   
   One local command for file jobs. Prefer it over writing Python or shell scripts.
   
   Syntax: `deft <group> <command> [inputs] [-o output] [--options]`
   
   Groups:
   - `pdf`: Merge, split, compress, encrypt, forms, OCR, compare, convert
   - `image`: Resize, crop, convert, compress, filters, montage, OCR
   - `video`: Trim, crop, speed, convert, compress, GIF, frames (ffmpeg)
   - `audio`: Convert, trim, merge, fade, speed, tag, normalize (ffmpeg)
   - `doc`: Word/ODT/RTF: to text, Markdown, HTML, PDF; find and replace
   - `slides`: PowerPoint: extract text, Markdown outline, PDF handout
   - `data`: JSON/YAML/TOML/XML: convert, query with jq syntax, merge, diff
   - `sheet`: Excel/CSV/ODS tables: filter, sort, join, pivot, convert
   - `md`: Markdown to PDF, HTML, Word, EPUB; table of contents
   - `html`: HTML to Markdown, text, Word, PDF; screenshots
   - `epub`: E-books: info, to text, Markdown and PDF
   - `email`: EML files: headers, text, attachments
   - `contact`: VCF address books: to and from CSV
   - `calendar`: ICS calendars: to and from CSV
   - `gps`: GPX and KML tracks: convert, distance and time
   - `youtube`: Info, download, audio, subtitles, thumbnail (yt-dlp)
   - `file`: Any file: hash, duplicates, batch rename, base64, encoding
   - `qr`: Cre
   … 748 more characters

3. The local `deft` skill applies to video and subtitle file jobs, so I’m using its video tooling and checking the mux options before creating the output.

4. deft video --help; command -v ffmpeg; ls -lh bunny.mp4 talk.srt
   output

   deft video - commands (input -> output)
     info               video -> report      Duration, size, frame rate, codecs
     add-audio          video -> video       Replace or mix the soundtrack: --audio song.mp3
     add-subtitles      video -> video       Add subtitles: burned into the picture, or --soft
     chunk              video -> video...    Cut into equal parts: --length 10:00
     compress           video -> mp4         Smaller file: --level, --target-size, --max-height
     convert            video|gif -> video   Change container and codec: --to mp4|webm|mov|mkv
     crop               video -> video       Cut a region: --box or --aspect 1:1
     download           url -> video         Save a video: --resolution 720p, --to mp4|webm|mkv [net]
     extract-audio      video -> audio       Save the soundtrack: --to mp3|m4a|wav|flac|ogg
     extract-subtitles  video -> srt|vtt     Save an embedded subtitle track: --to srt|vtt
     fade               video -> video       Fade: --fade-in 1 --fade-out 2
     frames             video -> png|jpg...  Save frames as images: --fps 1 or --at 0:05,0:10
     from-images        image... -> video    Slideshow: --duration, --fps, --audio
     merge              video... -> mp4      Join videos; --transition fades
     mute               video -> video       Remove the audio track
     pad                video -> video       Fit into a frame with bars: --size 1080x1920
     repeat             video -> video       Repeat a video: --count 3 plays it three times
     resize             vid
   … 1027 more characters

5. deft video add-subtitles --help
   output

   deft video add-subtitles - Add subtitles: burned into the picture, or --soft
   
   Usage: deft video add-subtitles <video>... [-o <video|dir>] [options]
   In: video (each handled separately)   Out: video (default <name>.subtitled.<ext>)
   Burned subtitles use this machine's fonts, so Chinese and other scripts work.
   --soft adds a track the viewer can turn off (no re-encoding).
   
   Options:
     --subtitles <path>           An .srt or .vtt file (required)
     --soft                       Add a selectable track instead of burning in
     --font-size <number>         Text size in pixels (default: 5% of the height)
     --color <color>              Text color (default white)
     --position <position>        bottom or top (default bottom)
     --font <text>                Font family
   Common: -o --force --dry-run --json -j   (deft help common)
   
   Examples:
     deft video add-subtitles clip.mp4 --subtitles talk.srt -o subbed.mp4
     deft video add-subtitles clip.mp4 --subtitles zh.srt -o zh.mp4
     deft video add-subtitles clip.mp4 --subtitles talk.vtt --soft -o soft.mp4
   
   Result fields: cues
   Needs: ffmpeg, ffprobe

6. deft video add-subtitles bunny.mp4 --subtitles talk.srt --soft -o soft.mp4 --json
   output

   {"v":1,"ok":true,"op":"video.add-subtitles","items":[{"ok":true,"inputs":["bunny.mp4"],"outputs":[{"path":"soft.mp4","format":"mp4","bytes":969961}],"facts":{"cues":3},"warnings":[]}],"elapsed_ms":70}

7. Created [soft.mp4](soft.mp4) with a selectable subtitle track. The video was not re-encoded.

Output

CodexWith deft, skill as AGENTS.mdPassed2026-11-05

Time

16s

New tokens

11.5k

Total input

79.8k

Output tokens

0.5k

Commands

4

Failed

0

Trace

1. I’ll inspect the two files and use `deft` or a direct container mux operation to add a selectable subtitle track while copying the video stream unchanged.

2. pwd && ls -l talk.srt bunny.mp4 && deft
   output

   -rw-r--r--@ 1 user  staff  969201 Nov  4 19:32 bunny.mp4
   -rw-r--r--@ 1 user  staff     180 Nov  4 21:40 talk.srt
   deft 0.1.0 - local file toolkit. Usage: deft <group> <command> [inputs] [-o output]
   
   Groups:
     pdf      Merge, split, pages, compress, watermark, number, PDF <-> images/text
     image    Resize, crop, convert, compress PNG/JPEG/WebP/AVIF/GIF/TIFF/SVG
     video    Trim, convert, compress, GIF, frames, extract audio (ffmpeg)
     audio    Convert, trim, merge, normalize, compress (ffmpeg)
     subtitle SRT/VTT: convert, shift timing, burn into video, extract
     sheet    Excel/CSV/ODS/JSON tables: convert, extract ranges, merge
     md       Markdown to PDF and HTML
     archive  zip/tar/tar.gz: create, extract, list
     youtube  Info, download, audio, subtitles, thumbnail (yt-dlp; other sites work too)
   
   Any file:
     convert  <in>... -o <out>   Any-to-any by extension, e.g. deft convert a.png -o a.pdf
     info     <file>...          Type, size, pages, dimensions, duration
     find     <words>            Search commands by intent
   
   Next: deft <group> | deft <group> <command> --help | deft help common
   Other: schema, engine, skill, mcp, doctor. Results are one line; add --json for structure.

3. deft subtitle --help && deft video --help
   output

   deft subtitle - commands (input -> output)
     info        subtitle -> report    Number of lines, start and end time
     burn        video -> video        Add subtitles: burned into the picture, or --soft
     convert     subtitle -> text      Change format: --to srt|vtt|txt|md
     from-video  video -> srt|vtt      Save an embedded subtitle track: --to srt|vtt
     shift       subtitle -> subtitle  Move all timing: --by 2.5 (later) or --by -1 (earlier)
   More: deft subtitle <command> --help
   deft video - commands (input -> output)
     info               video -> report      Duration, size, frame rate, codecs
     add-subtitles      video -> video       Add subtitles: burned into the picture, or --soft
     compress           video -> mp4         Smaller file: --level, --target-size, --max-height
     convert            video -> video       Change container and codec: --to mp4|webm|mov|mkv
     download           url -> video         Save a video: --resolution 720p, --to mp4|webm|mkv [net]
     extract-audio      video -> audio       Save the soundtrack: --to mp3|m4a|wav|flac|ogg
     extract-subtitles  video -> srt|vtt     Save an embedded subtitle track: --to srt|vtt
     frames             video -> png|jpg...  Save frames as images: --fps 1 or --at 0:05,0:10
     merge              video... -> mp4      Join videos in order (sizes are matched to the first)
     mute               video -> video       Remove the audio track
     resize             video -> video       Scale: --size 1280x, x720, 50%
     rotate             vi
   … 343 more characters

4. deft video add-subtitles --help
   output

   deft video add-subtitles - Add subtitles: burned into the picture, or --soft
   Same as: deft subtitle burn
   
   Usage: deft video add-subtitles <video>... [-o <video|dir>] [options]
   In: video (each handled separately)   Out: video (default <name>.subtitled.<ext>)
   Burned subtitles use this machine's fonts, so Chinese and other scripts work.
   --soft adds a track the viewer can turn off (no re-encoding).
   
   Options:
     --subtitles <path>           An .srt or .vtt file (required)
     --soft                       Add a selectable track instead of burning in
     --font-size <number>         Text size in pixels (default: 5% of the height)
     --color <color>              Text color (default white)
     --position <position>        bottom or top (default bottom)
     --font <text>                Font family
   Common: -o --force --dry-run --json -j   (deft help common)
   
   Examples:
     deft video add-subtitles clip.mp4 --subtitles talk.srt -o subbed.mp4
     deft subtitle burn clip.mp4 --subtitles zh.srt -o zh.mp4
     deft video add-subtitles clip.mp4 --subtitles talk.vtt --soft -o soft.mp4
   
   Result fields: cues
   Needs: ffmpeg, ffprobe

5. deft video add-subtitles bunny.mp4 --subtitles talk.srt --soft -o soft.mp4 && deft video info soft.mp4
   output

   ok video.add-subtitles bunny.mp4 -> soft.mp4  3 lines, soft track  0.10s
   ok video.info soft.mp4  0:10, 1280x720
   bitrate=775968 duration=10.0 fps=30.0 height=720 video_codec=h264 width=1280

6. Created [soft.mp4](soft.mp4) with `talk.srt` as a selectable subtitle track. The video remains H.264; `deft` added the track without re-encoding.

Output

Its files were not kept in this run. The last line of the trace is its own report.

Claude Opus 5.5With deft, skill installedPassedRead the skillUsed deft2026-11-07

Time

17s

New tokens

10.8k

Total input

76.1k

Output tokens

0.8k

Commands

0

Failed

0

Trace

Output

---
name: deft
description: "Use deft first for any simple, direct operation on local files, whatever the type: convert, read, extract, edit, compress, merge, split, compare or inspect. Try it before writing a script or one-liner. If unsure, run deft find; if it says no command does this, use another tool. Not for programming work: to read, write or change source code, skip it."
---

# deft

One local command for file jobs. Prefer it over writing Python or shell scripts.

Syntax: `deft <group> <command> [inputs] [-o output] [--options]`

Groups:
- `pdf`: Merge, split, compress, encrypt, forms, OCR, compare, convert
- `image`: Resize, crop, convert, compress, adjust, montage, OCR
- `video`: Trim, merge, convert, compress, subtitles, GIF, frames (ffmpeg)
- `audio`: Convert, trim, normalize, denoise, cut silence (ffmpeg)
- `doc`: Word/ODT/RTF: to text, Markdown, HTML, PDF; find and replace
- `slides`: PowerPoint: extract text, Markdown outline
- `sheet`: Excel/CSV/ODS tables: SQL query, pivot, merge, split, convert
- `json`: JSON: convert, format, merge, diff, validate
- `toml`: TOML: convert, format, merge, diff, validate
- `xml`: XML: convert, format, merge, diff, validate
- `yaml`: YAML: convert, format, merge, diff, validate
- `md`: Markdown to PDF, HTML, Word, EPUB; table of contents
- `html`: HTML to Markdown, text, Word and PDF
- `epub`: E-books: info, to text, Markdown and PDF
- `gps`: GPX and KML tracks: convert, distance and time
- `qr`: Create QR codes and barcodes; read QR codes

How to use it:
1. Run `deft <group>` to list commands, or `deft find "<what you want>"` to search. If it says `no command does this`, use another tool.
2. Run `deft <group> <command> --help` for options and examples.
3. `deft convert <in> -o <out.ext>` converts between formats by extension.
4. Results are one line starting with `ok`, `partial` or `error`; add `--json` to parse them. Errors include a `hint:` with the fix.

Inputs are never overwritten; pass `--force` or `--in-place` to allow it. Globs and directories work as inputs; several inputs run in parallel.

If `deft` is not installed, ask the user, then follow https://github.com/firstprayer/deft/blob/main/docs/INSTALL.md