Variable Bitrate Video player - can we build it?

Hi all, 

We will be creating a lot of film soon. For the best user experience we want a variable bitrate solution, as some of our customers are in places where they may have problems streaming a high-quality film. 

I'm thinking that using a test, like the one described here: https://www.expertsphp.com/how-to-check-internet-speed-test-using-javascript/

...we could test the users' connection speed, and give them a low-quality (i.e. smaller framesize) film if it is needed.

Has anyone done this? Can you think of any issues that I might face?

Thanks

Adam