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.

Avec l'outil "Shift Times" pour réajuster le timing complet d'un fichier de sous-titres :

The shift times tool is a batch processor for timestamps; it adjusts the start/end timestamps of many subtitle lines at once in various ways. It is located under Timing -> Shift Times.