Captioning for QuickTime
http://www.webaim.org/techniques/captions/quicktime/

WebAIM
2003

Abstract:

There are two methods for adding captions in QuickTime. There are advantages and disadvantages to each approach. The first allows you to maintain a single file, making the captioned video easier to distribute. The second approach allows you to easily deliver a captioned and non-captioned version of your movie, but requires an understanding of SMIL (it's not too hard).