Is there any chance you can add playback speed buttons to html 5 videos.
Looking at the jwplayer support site it appears it can be done but is only supported in chrome and safari at this time.
http://support.jwplayer.com/customer/portal/articles/search?q=playback+speed
Also it looks like the code is available for purchase for $50.
https://www.freelancer.ca/projects/Javascript/Add-speed-control-player-using.html
I have used this feature for some online courses and loved it!!!!