Burn Local Subtitles into Video

What it does

Burn existing local SRT or ASS text into the first video stream using FFmpeg/libass. Adjust font size, family, margins and outline. Optional font files are staged locally. Source paths containing a Windows drive colon, apostrophes, spaces or Unicode are never interpolated into the filtergraph.

How to use

Run the dry-run example below, review the plan and then remove --dry-run to render. Use a new MP4 path. Optional --fonts-dir accepts an existing directory of licensed TTF, OTF or TTC files; --font-name chooses the internal family name.

Requirements

Python 3.10 or newer and separately installed FFmpeg/ffprobe. No Python packages or binaries are bundled. FFmpeg must include libass/subtitles, libx264 and AAC; provide fonts with needed glyphs.

Caveats

No transcription, translation or subtitle proofreading. UTF-8 subtitles are recommended. Rendering reencodes video to H.264 and the optional first audio stream to AAC. Other streams are omitted. ASS inline styles and positioning may override style defaults. Inspect the result visually; fonts and glyph coverage differ by operating system. It does not download arbitrary YouTube URLs.