There are plenty of captioning resources out there for you to explore, learn and perhaps work with them for captioning needs. List below is the links that you can visit.
National Captioning Institute, Inc. (NCI), http://www.ncicap.org
Federal Communications Commission (FCC) on Closed Captioning, http://www.fcc.gov/cgb/dro/caption.html
National Center for Accessible Media, http://ncam.wgbh.org
Captioning Web, http://webaim.org/techniques/captions/
You can find further information on captioning via search engine sites, such as Google and Yahoo. Example of keywords to use for searching are: closed captioning, DVD subtitles, Blu-Ray subtitles, captioning, web captioning, media captioning...