A set of Unix/Windows command line tools for subtitle editing, conversion - currently, adjustsrt is available.
From the Author :
adjustsrt is a command-line tool used to adjust the subtitles of a .srt (SubRip) file to a specific movie file by increasing or decreasing the time stamps of this file.It is usefull, for instance, when you've just downloaded a DivX and the only subtitle you've found in your language doesn't match the video stream. You just have to shift the subtitles step by step using adjustsrt until it matches exactly the movie.
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