Yeah, humming should be bearings. It's not an easy noise to capture on video, but I can hear a little bit of an odd harmonic noise. I guess that's what you were describing.
There is nothing else on the rear end that could make a similar constant noise except for seized brakes or unevenly worn tires. It's unlikely to be the brakes, because that's usually a grinding or squeaking noise. If you want to be completely sure, you can check the brakes by listening to see if the noise changes dramatically while braking.
To check if your tires are making the noise, you can simply swap your rear tires up front and see if the noise moved.