Is it possible for two releases to have the same disc id?
For exemplification, see here:
same main release, but different version. Is this possible? I tend to say it is possible, especially with two releases of the same recordings and the CD manufactured in the same way. But in reality, what are the statistics on this? Is it realistically possible per historical data?
They will if they have the same sequence of frame offsets. I’m not sure how likely that is but apparently it does happen.
It’s theoretically possible otherwise, with a SHA1 collision, but extremely unlikely. (You’d need about 2^80 disc IDs in the system to have an appreciable chance of random collisions. Intentional SHA1 collisions have been constructed, but I don’t think there’s enough flexibility in the data format to pull it off in this case even if one were motivated enough to try.)
If you mean common https://musicbrainz.org/cdtoc/I4Ro8vFn9AAI0Chz.5E3quN._ss- I think it is totally unsurprising as they are two country editions of same master.
It should be the case with almost all albums. Except editions with bonus tracks out other track list discrepancies.
Ok, thanks for the replies. It seems I am right to question it and have a closer look, but given the specifics, the duplication is possible and could be ok.
I was just making sure that having such a duplicate is a real possibility. But it seems that there is real data to show this can and has happened.
There are two sides to this: As a disc ID is some kind of hashing (mapping the near infinite ammount of possibilities how the tracks are arranged on the disc onto a rather short string) it is totally possible that two completely unrelated discs might have the exact same disc ID, but it is very unlikely to happen. Still we might have those cases somewhere.
But your example is different: This is basically the same release in different packaging. This actually makes a matching disc ID very likely and not surprising at all. In many cases the same master is reused for re-releases.