Are bad sectors due to protective measures or do they point to defective disks?

[hvergelmir]

Hi,

I got a question.

So I ordered the Cornetto Trilogy (Simon Pegg and and Nick Frost) and of the first delivery the BD for "Shaun of the Dead" had bad sectors.

Well, I returned that and got a replacement. The replacement, however, also has bad sectors. They're not at an identical position, but some of them overlap (going by the sector numbers).

I tried ripping the image several times in order to find out if the bad sectors change between read attempts.

First attempt (original disk):

Error reading from drive F:!
Sectors: 3344520-3344549
Sectors: 3344550-3344579
Sectors: 3344580-3344609

First attempt (replacement disk):

Error reading from drive F:!
Sectors: 3344520-3344549
Sectors: 3344550-3344579
Sectors: 3344580-3344609
Sectors: 3344610-3344639
Sectors: 3344640-3344669

Second attempt (replacement disk):

Error reading from drive F:!
Sectors: 3344520-3344549
Sectors: 3344550-3344579
Sectors: 3344580-3344609
Sectors: 3344610-3344639
Sectors: 3344640-3344669

Now I'm wondering if these bad sectors are the symptom of some kind of protective measure or if this is outright a defective disk.

 

[Pete]

The read errors are all pretty much in the same place (all around 00:12:56 in the main movie).
Shouldn't result in much more than a small hiccup, though.

Definitely not a protection thing.
Bad pressings tend to come in batches (the master is defective and the whole batch is ruined).

 

[Ch3vr0n]

https://forum.redfox.bz/index.php?threads/71489/ troubleshooting item 1

Sent from my Nexus 6P with Tapatalk

 

[el Filou]

Regarding that troubleshooting thread, it states:

Blu-ray discs do NOT have a protection that simulates bad sectors on a disc.

but in the changelog for AnyDVD HD 8.1.8.0 you can find:

New (Blu-ray): Support for copy protection with read errors

Is this a misunderstanding? It's unclear if this references a new copy protection based on read errors or if it is some level of resilience from read errors on "standard" discs.

 

[Pete]

New (Blu-ray): Support for copy protection with read errors

Is this a misunderstanding? It's unclear if this references a new copy protection based on read errors or if it is some level of resilience from read errors on "standard" discs.

It should be updated, indeed.
Clarification: there is a certain type of protection, that works with read errors, but it is limited to BD-Rs (on-demand discs you can buy on Amazon, that are burned on regular writable discs, not pressed on BDROM, also no AACS).

 

[Ch3vr0n]

I asked about that in a pm a little while ago @Pete remember? @James was invited to the conversation too. He said since it was such a rare situation an mostly used on on-demand burned discs that I should NOT update it and leave it as is.

Sent from my Nexus 6P with Tapatalk

 

[Pete]

I asked about that in a pm a little while ago @Pete remember? @James was invited to the conversation too. He said since it was such a rare situation an mostly used on on-demand burned discs that I should NOT update it and leave it as is.

It still is really, really rare, but since it's in the forum, you might as well add the distinction, otherwise there's just confusion.
BTW: it's not "mostly" used on DOD discs, so far it's only applied to those (and not likely ever to come to be on any "real" commercial disc, due to its nature and being so embarrassingly amateurish).

 

[theosch]

Ah perfect. I considered to make a new thread asking whether RedFox offered a rescue product for optical media.
A bad sector protection probably would rule out to use ddrescue, but since it's really rare on BDs.
Still it's senseless to use ddrescue on DVDs with bad sector copy protection, isn't it?

What is this bad sector copy protection more exactly?
Is this wrong EFM (Eighteen-to-Fourteen-Modulation) -bit patterns on some DVD media using bad sector stuff?
Well it appears similar from some games on CD and/or DVD with "SafeDisc" copy protection but perhaps I'm confusing this.

 

[hvergelmir]

Definitely not a protection thing.
Bad pressings tend to come in batches (the master is defective and the whole batch is ruined).

Thank you, glad to hear that. So all said I'd have to look for a different edition (e.g. not in the form of the trilogy) to get a working BD, I guess. Or somehow get a hold of a different batch (but I don't want to keep asking for replacements until the trader gets annoyed).

 

[Ch3vr0n]

Bad sector protection (at least on DVD's), is a form of protection where "useless/fake/corrupt looking" data is written to sectors i believe SIMULATING bad sectors on a disc. These arent really bad sectors. But actual bad sectors (scratched) obviously do exist as well. If this is the same for BD's, i don't know.

@Pete sticky has been updated. Care to take a look if that's good enough for ya?

https://forum.redfox.bz/threads/please-read-this-before-you-post.71489/#post-456463

 

[hvergelmir]

Bad sector protection (at least on DVD's), is a form of protection where "useless/fake/corrupt looking" data is written to sectors i believe SIMULATING bad sectors on a disc. These arent really bad sectors. But actual bad sectors (scratched) obviously do exist as well. If this is the same for BD's, i don't know.

Obviously I don't know for certain, but two BDs with similar bad sectors just struck me as odd. So I don't think these are scratched but due to a bad master as @Pete pointed out. Thanks again.