Generating a UID for optical media

[osgZach]

I'm curious to hear from people in the know, what methods may be used to generated unique ID's from optical media. Namely BluRay and DVD Discs.

Mainly this is for a database, to store some information.
Are there certain characteristics that are checked against? On the one hand you could pretty easily tell a DVD from a BRD by looking at the directory structure, but what about identifying Discs from the same pressing?

Is there anywhere on the disc you can read for some sort of serial number or other identification? What about different pressings of the same movie? How do you tell they are the same movie but just might be a different pressing?

Also there is the concern of the "same feature" that is a different version, like a Director's Cut vs Theatrical Cut.

Does copy protection affect various methods of identification? (i.e if you hash a disc decrypted by Software like AnyDVD will the same disc simply put into the drive match or be completely different)

I'm just trying to understand what common factors I might be able to Hash against, as opposed to a "Title" created by User Input, etc.. The proposed database system would also use user input to verify / upvote "verified" correct data, while allowing to cull "bad" entries; so I'm wondering if just hashing the title input by the user would be enough and not worth the effort to go further. I'd like to be able to reject "duplicate entries" to a various degree while still allowing some dupes through for judgement.