This is a significant UI issue, and IMO is a bug. The view page shows the player, with the captions included. There is a preview button, and it doesn't show the player - preview does nothing except show the raw text that is visible in the edit box.

mdale wrote:

I think this would be kind of tricky to support. We would probably have to leverage the draft extension or something.

I think it would be better to restore the universal subtitles module:
http://blog.wikimedia.org/2010/10/14/video-labs-universal-subtitles-on-commons/

That would gives you a realtime preview and tools to do micro alignment.