How to get 5.1 audio in Google Chrome?

Update: [As of Jan 13 - 2020] Now this option is GONE and the feature appears to be active by default (since version: 79.0.3945.117)
So nothing needs to be done. You can verify with a true 5.1 audio file played through the browser. https://www2.iis.fraunhofer.de/AAC/multichannel.html

In order to up-mix stereo signal into a multichannel audio - you need to look into the options of your sound-card driver instead.

I use the old Creative X-Fi MB3 software to do that for me.

[Previously i.e. before Chrome 79]
Go to chrome://flags and enable #try-supported-channel-layouts flag; relaunch.

chrome://flags/#try-supported-channel-layouts

This way it worked. Chrome::Youtube surround sound on my 5.1 speakers finally!

I could not get it working via the command line options. And perhaps the other command line options are now deprecated. Generally too, I recommend using the flags instead of the command line params

Ive been looking for the same answer and finally found it so I thought I have to share it with you(and others with the same problem). The solution for me was to put " --force-wave-audio" at the end of the shortcut. I hope it helps others too!