SSA (SubStation Alpha) and SRT (SubRip) are file types that store video (movie) subtitles and as such can be converted between these formats via ssa to srt conversion. This can be achieved using several subtitles editors, such as the popular Subtitle Workshop.
Simple edits and other changes can also be done using any text editor, considering both files are essentially specially formatted text files. You just need to make sure that you do not screw up the existing formatting of the file.Open SSA file Open SRT file
A tool for creating and modifying subtitles
A program for editing of text subtitles for videos
Small tool for macOS, which allows users to convert ass, ssa, s2k, smi, sub files to SRT format
A free subtitle editor
An online converter for subtitles
An older freeware subtilte editing application