Subtitling is a function mostly of higher-end DVD-creation programs (I
ASS-U-ME that we're talking here about self-created DVD's?) - which are not
cheap - there are a few options though.... (note that the links are UK
ones! - your region may vary both in price and availability). Synchronising
the subtitles to the spoken word is a long and arduous task for anything but
a short(<10min) clip, even if you have the full script already on file.
Have a look here.... http://www.pcw.co.uk/software/video-recording-editing-and-mixing