Sound input with 2+ user accounts

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Király - 31 Dec 2005 05:49 GMT

Hello, I'm reposting this from comp.sys.mac.system; I got no responses
there. :(

I have an eMac with built-in microphone and analog audio line-in jack.
In System Preferences -> Sound -> Input, I can select between the mic
and the audio line-in port. This seems to be a global preference setting;
whenever a user changes it, that change is in effect for all
other users. A few questions about this:

1) How is it that a non-admin user can change this global preference
without authenticating with an administrator's username and password? Is
this a bug or a feature?

2) Where is this preference stored? I had a look inside
/Library/Preferences/com.apple.audio.DeviceSettings.plist, but I don't
see anything in there that looks like it, and also that file's
modification date is older than when I last set the input device.

3) Is there any way to make this preference account-specific?

TIA
K.

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Brian Hughes - 31 Dec 2005 08:50 GMT

> Hello, I'm reposting this from comp.sys.mac.system; I got no responses
> there. :(
[quoted text clipped - 4 lines]
> whenever a user changes it, that change is in effect for all
> other users. A few questions about this:

The settings for this preference are kept in a hidden binary plist file
in the users preferences ByHost folder:
~/Library/Preferences/ByHost/.GlobalPreferences.xxxxxxxxxxxx.plist where
the x's are a hexadecimal number.

So the file says "Global" but it exists for each user in a ByHost
directory. For this reason I'm not sure I can answer your questions.
Maybe someone else can explain how these are used and if they are really
global.

If it is a global setting, the reason it's not secured is that it's not
a security issue. Apple only locks those preferences that make
permanent changes like network or startup disk settings.

BTW, that preferences file also contains the setting for sound effects,
alert volume, alert sound, font smoothing, a mouse button swap setting,
and some ColorSync settings.

It also looks like it gets corrupted easily, at least mine looks like it
from the Property List Editor. In your case you might try deleting the
file and changing your preferences. Also if you don't want a non-admin
to change the settings, move the Sound.prefPane from
/System/Library/PreferencePanes to ~/Library/PreferencePanes of an admin
user.

Signature

Brian Hughes
usenet at hughesvideo dot com

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Király - 31 Dec 2005 22:33 GMT

> The settings for this preference are kept in a hidden binary plist file
> in the users preferences ByHost folder:
> ~/Library/Preferences/ByHost/.GlobalPreferences.xxxxxxxxxxxx.plist where
> the x's are a hexadecimal number.

Thanks for that info, that's very helpful!

What I want to do is set the preference in one user account so that the
input device is always set to the same. My wife uses the internal
microphone to talk on Skype under her own account, and whenever I switch
the input to line-in in my account to record audio, the same change is
made under my wife's account. Then when my wife tries to use Skype the
microphone is turned off until she goes to the System Prefs and sets
the input device back to microphone again.

I tried logging into my wife's account, setting the pref, finding that
hidden prefs file, and locking it with Get Info, but it didn't help.
Logging in as me and setting the input back to line-in still made the
same change under my wife's account.

Thanks for the help, though! I'll tinker around with this a little more
and see if I can't rig something up.

K.

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Mac Forum / General / Hardware / December 2005

Sound input with 2+ user accounts