I have several VHS tapes with subtitles. These are all old movies.
Some of them are released on DVD now, but with no subs.

I was wondering if there is a method to scan those subtitles with an OCR tool or something?

proces: VHS tape -> digitizing -> AVI (or similar) -> OCR tool -> SRT file (or similar)

I guess DSubtitler is not suitable for this, because even if I digitize the VHS tape directly to DVD, there won't be a subtitle stream in the VOB container to analyze.