srt

There are heaps of subtitle editors for Windows, but I found only one usable for Linux: ksubtile. It's not perfect but usable. It uses SubRip format (*.SRT). In these files subtitles have a running number, end- and startime down to milliseconds given for each subtitle. The import function of subtile fails occasionally, but you can use mplayer to convert subtitle files into srt format. BTW: If your movie and the subtitle file have the same name and are in the same directory they will be loaded automatically by mplayer (unless you switch this function off).