[PLUG] Audio hum when playing Blu-ray movie

[John Jason Jordan]

You can't play Blu-ray movies on Linux, right? Wrong. You can if you
give $50 for a license for MakeMKV. Not only will MakeMKV for Linux rip
and encode a Blu-ray movie to a .mkv file, if you follow the
instructions in their forums you can get VLC to play the discs
directly. 

I did this successfully on my laptop first, as that is my usual
platform for making .mkv files. It works perfectly. But I use my
desktop for viewing movies, so that was my next step. Both machines are
Xubuntu 14.04. The desktop installation went perfectly and MakeMKV sees
and will rip and encode a Blu-ray movie. (Both machines have Blu-ray
drives.) I followed the same instructions on the desktop as I did on the
laptop for getting VLC to play a Blu-ray movie, and it does so, but
there is a loud hum, loud enough to drown out the audio in the movie. I
would say it is a 60-Herz hum, except that it seems just a bit higher.
This is strange because the desktop spends all day streaming internet
radio stations to my stereo, and the output is beautiful - no hum. And
the laptop play the same Blu-ray movie without hum.

There is a difference in the source of the audio signal, of course. For
internet radio Banshee is connecting to the stream and sending the
audio signal to the stereo. For the movie the source is the Blu-ray
drive, although I don't know how it is processed into the signal that
goes to the stereo. Note that the same Blu-ray drive on the desktop
plays DVD movies without the hum. (I currently own only one Blu-ray
movie.) It also plays television over the air through my HDHomeRun
tuner, which uses VLC, also without issue.

I poked around in Pulseaudio volume control on the desktop and failed
to resolve the problem. 

I need some clues.