Converting Vobsub (.sub/.idx) to .srt in Linux

Mencoder rips the subtitles for you as I just posted. But what if you want a .srt file? The problem is that vobsub subtitles used in DVDs are made as images. This means you first need to convert the images back to text. That is usually done with the help of OCR. And not differently for subtitles. But there's already a special open source Linux program available for that purpose here.