When you use the backup option on a DVD in MakeMKV, is the ISO created a perfect 1:1?
Similarly, backup bluray structures are 1:1 as well?
Is Backup on a DVD a perfect 1:1 ISO copy?
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christopher2222
- Posts: 41
- Joined: Sat May 11, 2024 8:07 pm
Re: Is Backup on a DVD a perfect 1:1 ISO copy?
It kinda depends on how you define 1:1. Decrypted backup obviously can't be 1:1 because what's on the disc is encrypted. But if your definition is like "is the decrypted data exactly what got encrypted by the disc maker", then I guess most of the time the answer is yes -- CSS/AACS decryption is not a process of "guessing" (although for DVD the keys are sometimes obtained through brute-force attack).
There are "complications" like ARccOS in some DVD titles though, in which case it is somewhat hard to define what's 1:1 (IMHO), and it seems that MakeMKV does not necessarily always handle it correctly / "perfectly". I don't know about it well enough to tell whether that could actually mean that the decrypted (VOB) files (which are what really matter) can then be somewhat not "perfect". (It might merely make the filesystem somewhat technically corrupted / imperfect.)
Also I think there are (meta)data on both DVDs and BDs that are not stored in the "normal" logical blocks, which also means that it is not contained by the filesystem and hence will not usually be written to the "ISO" (somewhat really a UDF filesystem image). For BD there's at least the BD-ROM mark (which I think would be written to discatt.dat when you make an encrypted backup with MakeMKV). I think there's something similar in commerical DVD-Video but I'm not sure. (Regardless, even if that's the case, unlike for BD / UHD BD it is no longer needed at this point for either MakeMKV or libdvdcss to decrypt the respective encrypted DVD / DVD "ISO", at least for most of the time.)
Recently someone also mentioned things like "layer breakpoint" in the case of dual layer DVD, which might be considered a piece of "metadata", but it isn't exactly "stored" on a disc -- but like a "fact" of the disc. If you consider the lack of that means "not 1:1", then well...
There are "complications" like ARccOS in some DVD titles though, in which case it is somewhat hard to define what's 1:1 (IMHO), and it seems that MakeMKV does not necessarily always handle it correctly / "perfectly". I don't know about it well enough to tell whether that could actually mean that the decrypted (VOB) files (which are what really matter) can then be somewhat not "perfect". (It might merely make the filesystem somewhat technically corrupted / imperfect.)
Also I think there are (meta)data on both DVDs and BDs that are not stored in the "normal" logical blocks, which also means that it is not contained by the filesystem and hence will not usually be written to the "ISO" (somewhat really a UDF filesystem image). For BD there's at least the BD-ROM mark (which I think would be written to discatt.dat when you make an encrypted backup with MakeMKV). I think there's something similar in commerical DVD-Video but I'm not sure. (Regardless, even if that's the case, unlike for BD / UHD BD it is no longer needed at this point for either MakeMKV or libdvdcss to decrypt the respective encrypted DVD / DVD "ISO", at least for most of the time.)
Recently someone also mentioned things like "layer breakpoint" in the case of dual layer DVD, which might be considered a piece of "metadata", but it isn't exactly "stored" on a disc -- but like a "fact" of the disc. If you consider the lack of that means "not 1:1", then well...
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christopher2222
- Posts: 41
- Joined: Sat May 11, 2024 8:07 pm
Re: Is Backup on a DVD a perfect 1:1 ISO copy?
I suppose I could compare the file sizes within the ISO and compare them to size on the disc. If they're way out, then I'll know they aren't 1:1.
So compared to WinX DVD copy pro, they advertise it as a 1:1 copy. Reason I like MakeMKV is because if there's errors MakeMKV will show it while WinX DVD copy pro only shows it on the fly and if you miss the error being fixed (ie a scratched area on the disc) you'll never know if you have a good or broken copy/backup.
So compared to WinX DVD copy pro, they advertise it as a 1:1 copy. Reason I like MakeMKV is because if there's errors MakeMKV will show it while WinX DVD copy pro only shows it on the fly and if you miss the error being fixed (ie a scratched area on the disc) you'll never know if you have a good or broken copy/backup.