Actually I just want to put this as a kind of Wiki, after breaking my fingers on this.
- How to automatically start video when in viewport.
- Most importantly: WordPress compatible solution PURE JavaScript. No JQuery. Why? Because newbies like me have a hard time “enqueing” libraries into wordpress… When even just receiving a scroll event is hard…
Anyway, posting answer below:
So – A straight forward, shortest solution is for creating a video on an html page, or indeed use a “raw HTML” element in WordPress: