Originally created as tool to make typesetting, particularly in anime fansubs, a less painful experience,
Aegisub has grown into a fully fledged, highly customizable subtitle editor.
It features a lot of convenient tools to help you with timing, typesetting, editing and translating
subtitles, as well as a powerful scripting environment called Automation (originally mostly intended for
creating karaoke effects, Automation can now be used much else, including creating macros and various
other convenient tools).