Alternate library - Airtunes and AppleTVs

Question

My iTunes library needs a tidy up as I have a lot of referenced entries with broken links or untagged content.
Thought I would create an alternate library (i.e. database and media files/folders not just the folder of media) on a non-boot internal or external drive, and repopulate from scratch and tidy up along the way.
I couldn't remember in the past if I had to authorise an alternate library again, it would seem not having added a recent music purchase to this from the old library.
Interestingly even though the library name is the same as the other in iTunes Preferences, as well as the top level folder simply being called iTunes as before, the AppleTVs do not appear for syncing/streaming but they are available for Airtunes playback.
Perhaps it's obvious in a way, but this simply reaffirms a previous observation that when AppleTV Devices disappear from iTunes for some reason, these units are still accessible as Airtunes speakers consistent with them using different communication protocols.
Even though all previously registered AppleTVs are listed in the Preferences, they do not appear as Devices - many Preferences seem to be shared between alternate libraries, but clearly some parameter that allows syncing / streaming doesn't, perhaps some unique library ID number. It just seems odd that Devices registered to another library show up, but the actual Devices don't - perhaps AppleTV stores some parameter that does not match to allow the Device negotiation.
Message was edited by: Alley_Cat

Answer 1

Winston Churchill wrote:
Sorry AC, I found it a little hard to follow what it is you observed, it's probably me not you, just finished 2 x 12 hr days doing accounts and my head is pounding.
I'm probably rambling a bit anyway, commenting on things as I find them.
The question, I guess is, does anyone know where the iTunes Device list is actually stored.
The list of devices isn't stored anywhere, they are listed when they become available, if you turn a device of it will disappear from the list (you may need to refresh). They will only appear though if there is a pairing established in preferences (or if the tv is advertising it's services after entering a passcode)
After a bit of delving around the AppleTV device names seem to be in an iTunes plist, but the associatd info is encoded and difficult to decipher.
The list of AppleTVs in Preferences seems to be shared between alternate libraries, so is presumably stored outside of the itunes main folder.
As a result of your observation I'm assuming you are not using an alternate user account.
No I've just opened iTunes holding the option key and created a new iTunes top level folder on an internal non-boot drive.
Each user has a preference file associated with iTunes which is stored in user/library/preferences. Changing the library that is used with iTunes won't change the preferences.
So you would assume, but the AppleTVs registered under another library of the same user account do not appear as devices even though they list under the iTunes>Preferences>AppleTV tab.
If however you were to set up iTunes under another user account, you would have different preferences.
Yes
Interestingly too, as the Devices do not show up in an alternate library without adding them as a new library..........
As I say I don't fully follow that, but if I'm understanding you correctly that shouldn't happen.
Yes, it's odd.
The iTunes Library.xml files have an entry for:
<key>Library Persistent ID</key><string>xxxxxxxxxxxxxx</string>
where the x's are a 'unique' hexadecimal value for each library even under the same user account - I suspect AppleTv itself may use this value to know which libraries it is associated with, though manually editing this value doesn't make devices appear in alternate libraries for the user account.
As for authorisation it is each computer that is authorised. If you set up 16 user accounts on one computer, you could share another computers library 16 times and it would only use up one authorisation.
Just being wary of multiple authorisations on the same computer which can happen I believe.
I recently used the option to reset all (5) authorised computers, which I can't use again for a year and am just being a little cautious.