whispersub 1.5.0

Transcribe videos to ASS subtitle files in 99 languages using faster-whisper

whispersub

Transcribe video files to ASS subtitle files using faster-whisper. Whisper detects the spoken language automatically and supports 99 languages, including English, Spanish, French, German, Japanese, Chinese, Arabic, Hindi, and many more.

• NVIDIA GPU acceleration with automatic CPU fallback
• Batch mode: pass multiple video files or directory trees
• Surround-sound audio extraction (dialogue-channel aware)
• Word-level timestamps with balanced line breaking
• Per-word confidence colour coding in the terminal

Requirements

Python 3.10+. Works on Linux, Windows, and macOS. No system FFmpeg needed — PyAV bundles its own. Supports MKV, MP4, AVI, MOV, WebM, TS, and other common video formats.

Install

pip install whispersub

GPU acceleration (Linux/Windows — requires an NVIDIA GPU with CUDA 12):

pip install whispersub[gpu]

Without [gpu], whispersub falls back to CPU automatically if CUDA is unavailable.

On first run, whispersub downloads the Whisper large-v3-turbo model (~800 MB) from Hugging Face and caches it locally.

Usage

# Single file — writes movie.en.ass alongside the video
whispersub movie.mkv

# Explicit output directory
whispersub movie.mkv --output-dir ~/subs

# Whole directory, force overwrite
whispersub /media/shows --force

# File with multiple audio tracks — inspect, then pick one
whispersub series.mkv --list-audio-tracks
whispersub series.mkv --audio-track 2

Options

Option	Default	Description
--audio-track N	—	Audio track index (required if the file has multiple tracks)
--list-audio-tracks	off	Show audio tracks for all input videos, grouped by configuration, and exit
--colour-by	probability	Per-word terminal colour coding: probability or duration
--font-size N	48	Font size (1280×720 canvas; player scales to actual resolution)
--force	off	Overwrite existing subtitle files (keeps backups)
--keep N	3	Number of .bak copies to keep when overwriting
--limit N	—	Stop after N segments per video (useful for testing)
--max-line-count N	2	Maximum subtitle lines per card
--max-line-width N	36	Maximum characters per line
--max-threads N	all cores	CPU thread limit
--output-dir DIR	alongside video	Write all subtitle files to this directory

Output

Subtitle files are named <stem>.<language>.ass, e.g. movie.en.ass. The detected language comes from Whisper. Output is compatible with VLC, mpv, IINA, MPC-HC, and other players that support ASS/SSA subtitles.

We chose ASS over SRT for better-looking subtitles: font sizing scales correctly to any resolution, and line breaks are balanced for readability. It also allows us to preserve word-level timing, so the file can be post-processed or reformatted without re-transcribing.

Licence

MIT