Whisperer lets you generate subtitles for any kind of video/audio files.
It uses OpenAI's whisper, it runs as many instances simultaneously as your GPU's memory allows.
Update: now uses https://github.com/Const-me/Whisper GPU enabled whispercpp, thanks to Kosta for this major speed improvement!
You will need the models from here: http://198.100.146.225/Downloads/whisper-modes/
Requires ffmpeg on your path, not included.