Open-source video transcoder

HandBrake is an open-source, GPL-licensed, multi-platform video transcoder.
It takes videos you already have and makes new ones that work on your
mobile phone, tablet, TV media player, game console, computer, or web browser.
Supports a wide range of input formats and outputs MP4 and MKV containers
with H.264, H.265, VP9, and other modern codecs.
Features include batch processing, subtitle support, chapter markers,
and built-in presets for common devices.