If you are a DVD maker and subtitle is your mandatory item, then you must use this software.
To make a DVD, DVD Lab Pro is a best DVD authoring software. (you can find dvd lab pro here -http://www.mediachance.com/dvdlab)
And to use this software you need separate video, audio and subtitle stream. And subtitle must be in right form (Format).
You can use this software for convert subtitle to DVD lab supported format.
For details please visit this link:
(http://siamcomputer-jsr.blogspot.com/2009/04/subtitle-helper.html)