DVD: Degradable Versatile...

jomaree writes "The SMH online reports that some DVDs are starting to corrode or "rot". Although somewhere between 1 and 10 per cent of DVDs are affected, it seems the distributors don't want to know. One list of affected movie titles reveals what might be a sinister pattern emerging: "One DVD website lists 18 titles known to have at least one bad batch, among them Planet of the Apes (1968), Men in Black: Collectors Edition, Independence Day and the Alien Legacy box set." Or maybe the person compiling the list only buys sci-fi movies."

Comments

This has happened to me

[krin]

I had a DVD that was released in 2000 start to lose quality, also I noticed that the layers seemed to be seperating. I take good care of all my cds and dvds, so I knew it was no fault of mine. I contacted the company who pressed the dvd and they offered to send me a replacement as long as I sent in the original.

Re:Bad DVD player!

[Spellbinder]

no this problems are known...
it is not just his dvd player

Re:Original site - karma whore

[westyx]

Please don't spank that server too hard - i know the person involved (friend of a friend) and they only have a 6 gig limit for the month.

Try reading the story

[westyx]

There are no walmarts in .au.

*bzzzzt* Thankyou for playing. Please come again.

IANAC (I am not a chemist)

[The Mutant]

but I do know that CD's and DVD's are both the same in that the are physically constructed of several layers.

Each layer consists of various polymers, and although sealed polymers are susceptible to degrading. Even though they are realtively robust compared to say, videotape, the weakest part of a CD or DVD is the side where information is made available to the reading device.

Polymers can react with moisture or UV light, and once that reaction starts (this is where a *real* chemist should start to add some meat to this discussion) it throws off by products that cause further degradation.

CDs and DVD's do ship with a protective layer that is intended to shield the delicate, information carrying sublayers but once damaged (i.e., scratched), the degradation process can begin.

Apparently if you store them properly - low humidty and at about 8 to 10 C, even damaged CD's and DVD' s will remain stable indefinitely.

Re:IANAC (I am not a chemist)

[Bob.Kerns]

I'm not a chemist either, but I remember enough from my metalurgy class at MIT to add something here -- plus I have practical experience with both polymers and metals in adverse circumstances: boats.

What you say is true, but misses the real issue: Polymers are generally *relatively* stable, compared to most things. And right next to the polymer is something which is decidedly NOT stable!

Have you heard of thermite? The thermite reaction involves the oxidation of aluminum, and aluminum is VERY hungry. It will actually steal oxygen from from iron oxide (rust) under the right circumstances -- and release a lot of heat in the process. (But aluminum oxide is more voluminous and stronger than aluminum, and quickly seals off exposed aluminum behind a thin layer of oxide. That's why your beer can isn't on fire inside your fridge.

But exposed aluminum is very reactive. Freshly-machined shavings of aluminum can catch fire.

It's the aluminum that's reacting. What is it reacting with? Several possibilities that I see:
1) Impurities in the polymer.
2) Impurities in the alumnimum deposition.
3) Impurities in the adhesive.
4) Impurities migrating through the polymer.
5) Impurities migrating in from the edge via the adhesive and/or the metal layer itself.

It could be a combination:

Dissimilar metals in contact set up a battery, if anything is available to complete the circuit. For example, put a brass screw into salt water, and before you know it, all the zinc will disolve and the screw will crumble into copper dust. Either metal by itself will do just fine in salt water -- so long as they're not touching.

Impurities in the aluminum might be stable unless they get, e.g. moisture migration along the adhesive from the outside edge.

Impurities could be in the polymer, or generated from degradation of same, but that wouldn't explain the observed failure pattern, so I think we can tentatively rule those out as contributing factors.

From this, what you say about storing them under low humidity and temperature makes sense -- but I bet this only comes from theory. It would take a LOT of CD's and a LOT of time, and a LOT of work to reach this conclusion validly through statistical observation.

The site with the 18 titles...

[ChangeOnInstall]

I think I've found the site that shows the list of "rotting" DVD titles mentioned in the article:

http://www.pnc.com.au/~jmcmanus/dvdrot.htm

I'm surprised Titan A.E. isn't on the list. Both I and a friend of mine own this DVD, and we've both had our copies degrade to be nearly unplayable. Mine has spent its entire life in a 200-disc carousel, where none of the other discs have had any problems.

Yet another reason for fair use laws!

[Mipmap]

http://www.vcdhelp.com/dvdripping

Also reported elsewhere in Africa

[Anonymous Coward]

I'm in Nigeria at the moment, and people I work with have had CDs ruined by some sort of fungus that gets inside the disk.

It can be avoided, so they say, by keeping the disks cool and dry. One risk is taking disks out of an air conditioned building into the hot, humid air outside. Water condenses onto the disks and gives the fungus a hospitable habitat in which to grow.

If it is common in Africa, it's probably only a matter of time before it moves to other hot, humid countries. South America and Asia spring immediately to mind.

And who knows what will happen as global warming continues to have an effect.

Re:Possible DMCA killer?

[gvonk]

The thing is, and everyone on Slashdot seems to forget this, you DON'T have to break the css to copy a dvd!!!!
Your player decodes it when you play it!
Copy it with the CSS!

That would be the first such DVD ever...

[Kjella]

Also, even though Divx is pretty good you can still tell a major difference in picture quality (especially if the DVD is like 720p originally).

The maximum DVD resolution is 720x480, however that is 480p. 720p would be 1280x720, and there are no such DVDs. While divx rips usually have almost the same resolution (640x???), they have to resize the pixels (4:3 or 16:9 on DVD, 1:1 in DivX), which is the biggest cause of problems, particularly with lines that get jagged. Even with anti-aliasing, it's quite noticable if you look for it. But, I don't irritate over it, so for me it's completely ok.

Kjella

Re:Storage Medium for the Really Long Haul?

[silverhalide]

It's not bad for the long run, but there's a huge advantage to having data in the digital domain: replication. Once you have digital data, it's relatively trivial to move it to the latest and greatest format that will (supposedly) last a long time.

Re:Possible DMCA killer?

[kilonad]

You can't copy the CSS. The keys (or something like that) are on a region of the DVD that no consumer DVD burner can write to. So we're back to square one.