How to make Youtube videos automatically play fast?

Question

YouTube

YouTube HTML5 Video Player allows you to play videos faster, but for this you need to click each time in the player settings to speed up the video by 1.25, 1.5 or 2 times. And how can I set up fast playback by default ? I understand that you need to write an add-on for the browser? Then tell me approximately at least in which direction to dig: how can you even track the signals that the browser gives to the player, or is everything arranged differently there?
UPDATE: It seems that this cannot be done using standard means, you need to cut something of your own. In the comments to the video link given by dimonchik2013, it is indicated that you can use <> hotkeys to speed up / slow down.

Answer 1

https://www.youtube.com/watch?v=SQE2lPY0-YY