subline 0.1.2

Generate SRT/VTT subtitles from video files using faster-whisper

            _     _ _
  ___ _   _| |__ | (_)_ __   ___
 / __| | | | '_ \| | | '_ \ / _ \
 \__ \ |_| | |_) | | | | | |  __/
 |___/\__,_|_.__/|_|_|_| |_|\___|

  video in -> subtitles out

subline

Dead-simple subtitle generation for video files. Point it at a file (or a folder full of them) and get .srt or .vtt subtitles -- powered by faster-whisper.

subline movie.mp4          # auto-detect language, writes movie.srt

  .-------------------.
  |  movie.mp4        |
  '-------------------'
          |
          v
  +-----------------+       +-----------------+
  |  ffmpeg extract |  -->  | faster-whisper  |
  |  audio track    |       | transcribe      |
  +-----------------+       +-----------------+
                                    |
                                    v
                            .-------------------.
                            |  movie.srt        |
                            |                   |
                            |  1                |
                            |  00:00:01,000 --> |
                            |  00:00:03,500     |
                            |  Hello world.     |
                            '-------------------'

Features

• Auto language detection -- or pin a language with --language es
• Batch mode -- pass multiple files or a whole directory
• SRT & VTT output formats
• CUDA auto-detect -- uses NVIDIA GPU when available, CPU otherwise
• Multi-track aware -- picks the first audio track and tells you about the rest
• Skip existing -- resume interrupted batch runs with --skip-existing

Quick start

brew install ffmpeg                   # or: apt install ffmpeg
pipx install subline
subline movie.mp4

Requirements

• Python 3.10+
• ffmpeg and ffprobe on your PATH

  # macOS
  brew install ffmpeg
  # Ubuntu / Debian
  sudo apt install ffmpeg
  # Windows (scoop)
  scoop install ffmpeg
  

Install

# With pipx (recommended -- installs in its own environment)
pipx install subline

# Or with pip
pip install subline

Trouble installing on Python 3.14? Some dependencies (av) may not support 3.14 yet. Use an older interpreter:

brew install python@3.13
pipx install subline --python python3.13

Usage

subline [options] <path...>

Flag	Default	Description
--language CODE	auto-detect	ISO 639-1 language code (es, en, fr, ...)
--model NAME	turbo	Whisper model: tiny, base, small, medium, turbo
--audio-track N	auto (first track)	Stream index of the audio track to use
--format srt|vtt	srt	Output subtitle format
--output-dir DIR	next to source	Where to write subtitle files
--device DEVICE	auto	Force cuda or cpu
--skip-existing	off	Don't re-transcribe if subtitle already exists

Examples

# Single file, auto-detect language
subline interview.mp4

# Spanish audio, specific model
subline --language es --model medium lecture.mp4

# Whole directory, skip already-done files
subline --skip-existing ~/Videos/series/

# Multiple files, VTT output in a separate folder
subline --format vtt --output-dir ./subs ep01.mp4 ep02.mp4 ep03.mp4

# Force second audio track (0-indexed stream id from ffprobe)
subline --audio-track 2 foreign_film.mkv

Output

Found 3 file(s) | model=turbo | language=auto-detect | device=cpu

Loading model 'turbo' on cpu...

[1/3] ep01.mp4
  Using audio track 1 (spa)
  Extracting audio (track 1)...
  Transcribing 45 min of audio...
  Detected language: es (98%)
  [ 52.3%] 350 segments, 124s elapsed, ETA 1m53s
  Done: 671 segments in 3m58s -> ep01.srt

[2/3] ep02.mp4
  ...

Development

git clone https://github.com/fenelon/subline.git
cd subline
pip install -e ".[dev]"
pytest

License

MIT