Re: [PLUG] Audio hum when playing Blu-ray movie

[Bill Barry]

On Wed, Jun 21, 2017 at 10:10 PM, John Jason Jordan  wrote:

> On Wed, 21 Jun 2017 15:45:29 -0700
> Denis Heidtmann  dijo:
>
> >I do not know much about what you describe, but you could answer the
> >frequency issue by recording the sound into Audacity on the laptop.
> >(Assuming you do not have a 'scope.)
> >
> >Is there a chance that the connections which produce the hum include
> >two different AC powered devices with a (not quite) common ground?
>
> Since my original message I have discovered that the hum goes away
> on the desktop if I turn off the right channel in Pulseaudio (the movie
> has only stereo, not 5.1). I have no idea what this means.
>
> You probably turned down the microphone input or the line-in input or
something like that. Those inputs can cause hum even if there is no device
connected to them. If you haven't already you should probably not just turn
them down, but mute them and any other inputs you are not using. In
alsamixer you maneuver to the device and hit  the letter m to mute, your
mixer may vary.

Bill
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Re: [PLUG] Audio hum when playing Blu-ray movie

[Denis Heidtmann]

Clearly if the frequency changes it is not 60 Hz.  Is there a chance that
it is a feedback of some sort?  I have run into problems when had both the
input and output selected, but do not recall the details as it was a few
years ago.

On Wed, Jun 21, 2017 at 10:10 PM, John Jason Jordan  wrote:

> On Wed, 21 Jun 2017 15:45:29 -0700
> Denis Heidtmann  dijo:
>
> >I do not know much about what you describe, but you could answer the
> >frequency issue by recording the sound into Audacity on the laptop.
> >(Assuming you do not have a 'scope.)
> >
> >Is there a chance that the connections which produce the hum include
> >two different AC powered devices with a (not quite) common ground?
>
> Since my original message I have discovered that the hum goes away
> on the desktop if I turn off the right channel in Pulseaudio (the movie
> has only stereo, not 5.1). I have no idea what this means.
>
> I also compared all the settings in Pulseaudio on the laptop to the
> settings on the desktop. I didn't see any differences, except that
> some are different because the two computers have different audio
> processors, plus I don't know what all the settings mean.
>
> As for the frequency, I note that it goes up and down when I change
> settings in Pulseaudio. Even at its lowest it is higher than 60 Hz, so
> I doubt very much that it is related to household AC power. Besides, AC
> power might affect the stereo or the audio cables connecting to it, but
> the computer? After going through the power supply and its rectifiers?
> I could check it out in Audacity, but I doubt that doing so would
> reveal much.
>
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Re: [PLUG] Audio hum when playing Blu-ray movie

[Denis Heidtmann]

John,

I do not know much about what you describe, but you could answer the
frequency issue by recording the sound into Audacity on the laptop.
(Assuming you do not have a 'scope.)

Is there a chance that the connections which produce the hum include two
different AC powered devices with a (not quite) common ground?

-Denis

On Mon, Jun 19, 2017 at 10:33 PM, John Jason Jordan  wrote:

> 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.
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