PanoptoSpeed is a firefox add-on that lets you play videos at whatever speed you want (within reason). I made it to watch my lectures at an ungodly speed, while I was procrastinating watching those same lectures.
Firefox: https://addons.mozilla.org/en-US/firefox/addon/hyperpanoptospeed/
You drag the slider and pray you can take it in...... Not rocket science. (If your lectures are on rocket science, then I'm sorry. Just in general.)
Pull requests are welcome, although I can't imagine what else you'd want to add.
Tests?! What are those??