CDRs--Degradable?

[i_like_lectric_motors]

From Pc World:


The Disc Rot Myth

Media obsolescence isn't the only thing people fear after committing a personal library's worth of data to CDs and DVDs. But some worries--namely, fear of disc rot--are not fully warranted.

Like a bad seed, the myth of disc rot self-perpetuates, cropping up every now and again as a sudden and mortal threat to your copious collection of prerecorded and self-created discs.

The myth was once rooted in fact. It is true that back in the 1980s, with the first generation of prerecorded audio CDs, the edges of the discs were not always sealed properly, which allowed moisture to get into the disc. Replicated, prerecorded discs use aluminum for the reflective layer; when moisture came into contact with the aluminum on prerecorded discs, explains Byers, it in turn oxidized, causing the aluminum to become dull. "That's where the term 'rot' started," he says.

But that problem was quickly identified and overcome. "The manufacturers learned what was going on, so now the edges of discs are sealed with a lacquer," according to Byers. Though the problem is typically associated with CDs, Byers notes that the potential for interaction with oxygen is the same with both CD-ROMs and DVD-ROMs.

The so-called rot issue does not apply to recordable discs. For one thing, recordable optical media do not use aluminum; instead, they use silver, and very rarely gold, or a silver-gold alloy, for the reflective layer. "If the silver comes into contact with sulfates [i.e., pollution, or high humidity], it could affect the silver, but the likelihood of that is less than the likelihood of moisture coming into contact with the aluminum on prerecorded discs," says Byers.

Enduring Myth

The term rot has persisted, however inaccurately, as a means of identifying a plethora of problems with optical discs. "If you get a faulty disc and see a problem that you can visually see, you call it rot, but it could be the way the disc was manufactured," says Byers. "Or if it was subjected to extreme moisture and that moisture came into contact with the aluminum, it could be that the reflectivity has changed. It's not really rot, it's oxidation of aluminum. It should be a rare event on a disc, unless it's defective."

Beyond the realm of defective discs, improper handling can cause otherwise good discs to go bad. Since there's little protection between the label side of a CD and the data layer itself, "scratches on the label side can scratch the metal, and that will ruin the data," says Byers. It's not an issue for DVDs, though, since the dye layer is sandwiched between two plastic layers.

Byers observed a similar problem occurring with press-on labels: "For long-term storage, we recommend not using press-on labels on CDs; when these start to dry up, they can peel the metal right up, damaging data."

[KYYX4ever]

very interesting and informative, motors; thanks for posting.

I was also wondering: advice is to use "good quality" CD-Rs, or stick with brand names. What exactly is the problem with cheap-o CD-Rs ? Is it their surface integrity?

[Jimbo]

[quote][i]Originally posted by KYYX4ever[/i]
Really ?

I'd like to hear from more of you guys about whether CDs/CD-Rs rot or not. I sure hope not! I'm not up on technology, really, but I am not surprised. I still hope it's not true, though[:(]

Jimbo, what is this DVD-Audio you've mentioned ?[/quote]

OK, here is my take on CD/CD-RW rot.
It did happen in isolated instances in the past and occasionally still does happen but for the most part the problem is overstated and does not happen on every single CD, but it does happen from time to time and I have had it happen to me, especially with rough treatment in a car.

DVD-Audio is basically a CD but with about eight to sixteen times the amount of data on it. Supposedly the jump from 16bit to 24bit word lengths and a much higher sampling rate provide a much more detailed and realistic musical presentation.

If you want a very detailed and precise explanation you can go these two links KYYX4ever, and they should answer all of your questions.

http://electronics.howstuffworks.com/question344.htm
http://en.wikipedia.org/wiki/DVD-Audio

Audio
In digital audio, common sampling rates are:

8,000 Hz - telephone, adequate for human speech
11,025 Hz - 16 bit Stereo Wave Sound Files
22,050 Hz - radio
32,000 Hz - miniDV digital video camcorder
[b]44,100 Hz[/b] - audio CD, also most commonly used with MPEG-1 audio (VCD, SVCD, MP3)
47,250 Hz - world's first commercial PCM sound recorder by Nippon Columbia (Denon)
48,000 Hz - digital sound used for digital TV, DVD, DAT, films and professional audio
50,000 Hz - first commercial digital audio recorders from the late 70's from 3M and Soundstream
50,400 Hz - sampling rate used by the Mitsubishi X-80 digital audio recorder
[b]96,000 or 192,400 Hz[/b] - DVD-Audio, some LPCM DVD tracks, BD-ROM (Blu-ray Disc) audio tracks, and HD-DVD (High-Definition DVD) audio tracks
2.8224 MHz - SACD, 1-bit sigma-delta modulation process known as Direct Stream Digital, co-developed by Sony and Philips

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[KYYX4ever]

wow, thanks[:)]

That howstuffworks site is sooo cool; I just added it to my favourites. I was always interested in "how stuff works"...I was the kind of kid who'd take apart Mum's vacuum cleaner to see how it worked and then put it back together again. Sometimes it would even work properly afterwards!

[Bitter Almonds]

So what the hell IS that crackling sound in my [i]Echoes[/i] compilation?![:(!]

[Jimbo]

[quote][i]Originally posted by XXX[/i]
So what the hell IS that crackling sound in my [i]Echoes[/i] compilation?![:(!][/quote]

Well, it could be lots of things. It MAY be a sampling rate or encoding issue.
What sound card are you using and what programs are you using to do the final mix-down to MP3?

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[Bitter Almonds]

Maybe it's how the cd recorder copied it (I made the copy using an old Phillips cd recorder). I use crappy ol' Real Player for computer stuff. I have to go and check the original factory press to see if the crackle is from the source, from the machine, or from the cd-r. I noticed the same thing in a Section 25 song, which really pissed me off.

[Jimbo]

It sounds like an encoding issue.

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Fluffy bunny sez: Kill Hutter, kill Hutter...

[hutter]

XXX, that sounds like the same problems I had until I replaced my sound card and CD drive, and switched from RealPlayer to Windows Media Player. I wish I knew which of the three was the reason for the problem being fixed. Damn, I'm no help at all, am I?

[Bitter Almonds]

No, no. This cd wasn't made using a computer writer, although I do make compilations using Real Player too which sometimes have similar problems (Windows Media gives me a "tin" background noise whenever I copy stuff with it). The cd I'm talking about was made using one of those old skool cd-recorders from Philips.

It's one of these odd contraptions:

http://img.2dehands.nl/f/normal/9476655.jpg