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DVD bad sectors question

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DVD bad sectors question

Old 11-06-19, 06:28 PM
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DVD bad sectors question

Hi,
This is a technical question mostly just to appease my curiosity. I sometimes buy Region 2 DVDs. So I don't have to change my computer's DVD-ROM drive region code, I usually rip the DVD and keep the image file. I recently got one and it came back with blocks of unreadable sectors. ~10% bad. I thought it was just bad luck. I got another copy and had the errors in the same locations. Curious, I change the region on my drive to 2 and played the DVD. It played just fine. I did fast forward through everything, but I would think that big blocks of missing data should be noticeable. So my question is, what exactly am I seeing here? Is this a normal behavior for some DVDs. I haven't encountered any problems like this before. This is a DVD of a TV show, if that matters. Again, I'm just curious.
Old 11-06-19, 09:03 PM
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Re: DVD bad sectors question

This sounds like the behavior of a Panasonic/Matshita manufactured computer dvd drive.

If you look up the model number, does it start off with something like UJ-**** ?
Old 11-09-19, 10:41 AM
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Re: DVD bad sectors question

Hi,
My drive is actually an LG Blu-Ray RE drive model BH40N.
Old 11-09-19, 11:46 AM
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Re: DVD bad sectors question

What movie company released this particular problematic region2 dvd disc?

Does it happen to be somebody like Lionsgate, eOne, etc .... ?
Old 11-10-19, 11:50 PM
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Re: DVD bad sectors question

Originally Posted by morriscroy View Post
What movie company released this particular problematic region2 dvd disc?

Does it happen to be somebody like Lionsgate, eOne, etc .... ?
It's a UK release of a Marvel animated series. The company that released it was called Clear Vision.

I've done a little more research and found that some DVDs have bad sector copy protection. Could this be the issue? I honestly didn't know that this was a thing. I reminds me of what they did with floppy disks back in the day.
Old 11-11-19, 08:27 AM
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Re: DVD bad sectors question

If you look into the /VIDEO_TS directory on the disc, does it have a large number of files which sums up to over 10 gigabytes?

(For example the american versions of the 1990s X-Men cartoons released on dvd by Disney, had this type of weird extra copy protection).
Old 11-11-19, 10:53 AM
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Re: DVD bad sectors question

No, it looks pretty normal. 40 files and ~7.3 gigs of data.
Old 11-11-19, 11:09 AM
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Re: DVD bad sectors question

The only other way I can think offhand to determine whether there's any bad sectors copy protection drm, is to read the actual *.ifo files.

I use the IfoEdit.exe program to read the ifo files. (It is at videohelp . com). Google for it.

I usually just copy all the ifo and bup files into a seperate directory, and read them with ifoedit to see whether there's anything funny. Mainly reading through the program chains to see whether there are any cells which are jumped over by a normal standalone dvd player.
Old 11-11-19, 11:11 AM
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Re: DVD bad sectors question

If you have any other dvd discs which are known to have deliberate bad sectors copy protection, it will be a an exercise to cut your teeth on to figure out how such extra basketcase drm functions from reading the ifo files.
Old 11-11-19, 11:53 AM
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Re: DVD bad sectors question

I've run through commercially purchased DVDs through a disc scanning program, and it's not uncommon for them to show a lot of bad sectors, even though they play fine. I've assumed it was due to copy protection.
Old 11-11-19, 12:00 PM
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Re: DVD bad sectors question

Originally Posted by Josh-da-man View Post
I've run through commercially purchased DVDs through a disc scanning program, and it's not uncommon for them to show a lot of bad sectors, even though they play fine. I've assumed it was due to copy protection.
On a normal standalone dvd player, the cell(s) filled with deliberate bad sectors are never played at all. The commands in the program chains will tell a standalone dvd player to jump/skip over these sick cells entirely.

On the other hand, a computer program which scans sequentially through all the sectors on a dvd disc, will not know a priori that such "sick" cells are filled with unreadable bad sectors. This is the entire point of the deliberate bad sectors drm.
Old 11-12-19, 08:45 PM
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Re: DVD bad sectors question

Originally Posted by morriscroy View Post
On a normal standalone dvd player, the cell(s) filled with deliberate bad sectors are never played at all. The commands in the program chains will tell a standalone dvd player to jump/skip over these sick cells entirely.

On the other hand, a computer program which scans sequentially through all the sectors on a dvd disc, will not know a priori that such "sick" cells are filled with unreadable bad sectors. This is the entire point of the deliberate bad sectors drm.
So then I should be able to make an image by replacing the "sick" cells with all 0's or something, right? I'm not sure how this would then function as copy protection. With floppy disks, the program does a check to see if the "mistake" is there or not. This "mistake" is something that can't be reproduced by a home floppy drive when copying.
Old 11-12-19, 09:03 PM
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Re: DVD bad sectors question

Technically yes.
Old 11-12-19, 09:09 PM
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Re: DVD bad sectors question

There's not much detailed information about this type of extra basketcase drm on dvds and blurays.

This is something you would have to do a lot of your own research independently, to figure out how these drm schemes function.
Old 11-13-19, 12:25 AM
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Re: DVD bad sectors question

It's verboten to discuss much further here, but you can spot discs with this copy protection if the player either keeps displaying "SEARCH" a few times before the movie starts, or on some the screen stays black and the time counter takes a while to count beyond 1 second. Haven't seen any with this in a while, but I have at least one TV series disc that has that at the beginning of every episode.
Old 11-13-19, 08:41 AM
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Re: DVD bad sectors question

Originally Posted by bsmith1702 View Post
With floppy disks, the program does a check to see if the "mistake" is there or not. This "mistake" is something that can't be reproduced by a home floppy drive when copying.
Without going into specifics, the original dvd designers did not appear to have hardcore security on their minds. It turned out the dvd css algorithm was entirely cracked back in late 1999. It was a very poorly designed algorithm.

So any extra basketcase drm added to dvd discs, is built on top of the basic css encryption system and very little else. (ie. An underlying system with basically no security).

Old floppy disc copy protection drm schemes were much smarter than the dvd's security system. Anybody who is hardcore into cracking computer copy protection (such as video games) will tell you that any dvd/bluray copy protection drm is a complete joke to crack.
Old 11-15-19, 11:10 PM
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Re: DVD bad sectors question

Thanks for the info. Like I said, I was mostly just curious about a DVD that I thought was defective, then thought had a defective production run when I found a second copy. I was aware of the encryption schemes that were used, but had no idea that other forms of protection were used on DVD.

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