subtitle-burner
GitHub基于ffmpeg libass将SRT字幕烧录至MP4视频，支持CJK字体回退、H.264重编码及音频无损复制。专为Meta短剧后期设计，处理Windows路径转义，提供灵活的样式与分辨率配置。
Trigger Scenarios
Install
npx skills add opensquilla/opensquilla --skill subtitle-burner -g -y
SKILL.md
Frontmatter
{
"name": "subtitle-burner",
"metadata": {
"opensquilla": {
"risk": "medium",
"requires": {
"bins": [
"ffmpeg"
],
"anyBins": [
"python",
"python3"
]
},
"capabilities": [
"filesystem-write",
"process-control"
]
}
},
"entrypoint": {
"args": [
"--input",
"{{ with.input }}",
"--subtitles",
"{{ with.subtitles }}",
"--output",
"{{ with.output }}",
"--font",
"{{ with.font | default('Microsoft YaHei,SimHei,Arial Unicode MS,Arial') }}",
"--font-size",
"{{ with.font_size | default(42) }}",
"--margin-v",
"{{ with.margin_v | default(80) }}",
"--play-res",
"{{ with.play_res | default('auto') }}",
"--crf",
"{{ with.crf | default(20) }}",
"--preset",
"{{ with.preset | default('medium') }}"
],
"parse": "text",
"command": "python {baseDir}\/scripts\/burn.py",
"timeout": 600
},
"provenance": {
"origin": "opensquilla-original",
"license": "Apache-2.0"
},
"description": "Burn an SRT subtitle file into an MP4 via ffmpeg's subtitles filter (libass). Single-pass re-encode of video; audio copied as-is. CJK-friendly font fallback chain (Microsoft YaHei → SimHei → Arial Unicode MS → Arial). Used by meta-short-drama as the final subtitling step after merge."
}
subtitle-burner
Burns an SRT subtitle stream into an MP4. The video is re-encoded (H.264 + faststart), the audio is copied untouched. libass renders the text per ASS-style override flags, so Chinese / Japanese / Korean characters survive when the host has any of the listed fallback fonts installed (on Windows, Microsoft YaHei and SimHei ship with the OS).
Inputs (with:)
| key | required | default | notes |
|---|---|---|---|
input |
yes | — | Source MP4 path. |
subtitles |
yes | — | .srt path (UTF-8). |
output |
yes | — | Output MP4 path. Parent dir created if missing. |
font |
no | Microsoft YaHei,SimHei,Arial Unicode MS,Arial |
libass FontName fallback chain. First wins. |
font_size |
no | 42 |
Font size. When play_res=auto this is in source-video pixels. |
margin_v |
no | 80 |
Bottom margin in source-video pixels (because play_res=auto sets PlayRes to the input W×H). |
play_res |
no | auto |
auto probes the input MP4 for resolution; or pass WxH like 720x1280. Setting this makes FontSize/MarginV act in source pixels rather than libass's 384×288 default. |
crf |
no | 20 |
x264 CRF (0-51, lower = better quality). |
preset |
no | medium |
x264 preset. |
Output
Prints the absolute path of the subtitled MP4 on stdout. Non-zero exit on any ffmpeg failure; stderr tails the last 2.5 KB of the encoder log for diagnosis.
Dependencies
- ffmpeg ≥ 5.0 (libass support is standard in any modern build).
- Python 3.8+.
The script auto-locates ffmpeg via PATH; on Windows it falls back to
the winget Gyan.FFmpeg / scoop / chocolatey install paths if PATH
inheritance failed (matches the resolution logic in video-merger and
video-still-animator).
Path-escaping notes
ffmpeg's subtitles= filter is picky on Windows:
- Drive-letter colons (
C:/…) must be backslash-escaped (C\:/…). - The path uses forward slashes regardless of host OS.
- Single quotes inside the path get backslash-escaped.
The script applies these rules so callers don't have to.
Style chain
The force_style defaults render white text with a 2-px black outline
on a transparent background (BorderStyle=3), bottom-centred,
80 px above the frame edge. Override any of the --* flags via
with.* if you want a different look.
Version History
- 7f72a32 Current 2026-07-05 18:40
