This is version of a prototype Michael shared last year, 
his version works within an etherpad, and uses the browser 
extension Greasemonkey to load etherpad_mediafragments_xpub.js   
(also in this folder) into the page.

I was curious to explore a standalone non-etherpad version...
But an open question is how to store/save/export the annotations?

A possible connection with WebVTT files could maybe be interesting?
Hmm...