subtitle-burner

name	subtitle-burner
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. Uses a verified managed Noto Sans CJK font when available. Used by meta-short-drama as the final subtitling step after merge.
description_zh	通过 ffmpeg 的 subtitles 滤镜（libass）把 SRT 字幕烧录进 MP4；视频单遍重编码，音频原样复制。可用时使用经过验证的托管 Noto Sans CJK 字体。由 meta-short-drama 在合并后执行最终字幕步骤。
provenance	{"origin":"opensquilla-original","license":"Apache-2.0"}
metadata	{"opensquilla":{"risk":"medium","capabilities":["filesystem-write","process-control"],"requires":{"bins":"[Truncated]","anyBins":"[Truncated]"}}}
entrypoint	{"command":"python {baseDir}/scripts/burn.py","args":["--input","{{ with.input }}","--subtitles","{{ with.subtitles }}","--output","{{ with.output }}","--font","{{ with.font | default('Noto Sans CJK SC') }}","--fonts-dir","{{ with.fonts_dir | default('') }}","--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') }}","--ffmpeg-path","{{ with.ffmpeg_path | default('ffmpeg') }}","--ffprobe-path","{{ with.ffprobe_path | default('ffprobe') }}"],"parse":"text","timeout":600}

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 render through the managed Noto Sans CJK font. The font directory is supplied through OPENSQUILLA_MEDIA_FONTS_DIR by the managed toolchain. An empty/whitespace-only SRT is a valid no-subtitle request: the input video is probed, copied to the requested output, and reported as SUBTITLES_SKIPPED: empty without invoking libass.

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	Noto Sans CJK SC	One libass FontName; comma-separated names are not a fallback chain.
fonts_dir	no	managed environment	Directory containing subtitle fonts, normally supplied by OpenSquilla.
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).