I ripped a dvd (not a movie, but a documentary) into chapter to chapter vob format. I used subrip to try to get the subtitles for each vob in Chapter2 which contains 12 vobs. The first vob's subtitle is perfect but then the ones after it isn't in sync. DVD players can't detect it since the remaing subtitles doesn't start from 1sec. How can I fix this sync problem? I am not sure what to minus for the subtiles in order for it to be compatible for each individual vob.

Thanks in advance.