Aegisub is a free, cross-platform open source tool for creating and modifying subtitles. Aegisub makes it quick and easy to time subtitles to audio, and features many powerful tools for styling them, including a built-in real-time video preview.
Aegisub natively works with the Advanced SubStation Alpha format (aptly abbreviated ASS) which allows for many advanced effects in the subtitles, apart from just basic timed text. Aegisub’s goal is to support using these advanced functions with ease.
Link: Author
Download:Aegisub 3.2.2
Old Versions:
Aegisub r8942