I have my Chromecast with GoogleTV plugged into a monitor with speakers, so CEC isn't an option. I had assumed that the volume buttons on the remote would just control the AndroidTV system volume, but they don't do anything.

In fact, I can't figure out a way to adjust the volume at all. I've even tried Button Mapper, but the commands it has for volume +/- don't do anything, and it doesn't recognize the remote's volume buttons when I try to add a custom button.

Is there any way to control the OS volume if it's plugged into something that doesn't use a remote for volume control? If not this device, is there a different AndroidTV device that would work?

I mostly want to use this to cast to, but adjusting the volume control on my phone while casting doesn't do anything either.