Accessibility is something we take seriously here at Poodll. We work with a number of 3rd party player and components which we "wrap" in Poodll. We can not always control how accessible they are, but for our owqn recorders and players we do.
PoodLL uses templates for audio and video players, these are customisable and shareable.
You can read more about them here.
Some templates are designed specifically for captioned video. TOn the demo site you can see a video player with subtitles and an interactive transcript.
If you want to add transcripts to recordings, you would have to make them in some tool, e.g. http://www.subtitle-horse.com . This page explains a bit about how to use subtitles in PoodLL.