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this post was submitted on 23 Feb 2024
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Do they last more than 20 years in ideal conditions?
Optical discs are already incredibly resistant and shouldn't be expected to fail in your lifetime. Most of the times they do, it's either old media (cd and dvd both had physical flaws in design), damage, or mistakes in manufacturing.
There's really no reason for the discs to degrade. It's just stamped plastic.
When they say plastic takes [huge number] of years to decompose, they're talking about how long it takes to disappear completely. The usable lifetime for most plastic objects seems to be only a few decades. (I don't know about the specific plastic they use for optical discs, though.)
Pressed optical discs will last a very long time. The lifetime of burned discs depends on the type of dye that's used to store the data. Many of the early CD-R's would get corrupted after a few years, but that was solved a long time ago.
And then unsolved as of late by manufacturers cheaping out.
As an optical media enthusiast, I’ve done a fair amount of research into how, why, and when discs fail. Because the discs use two or more polycarbonate layers pressed together, moisture can sometimes work its way between the layers and speed up degradation, especially if a disc has been overly flexed at the center. Heat and UV can also speed up degradation.
Another problem is that plastic is petroleum-based and it breaks down over time. A lot of people think that the reflective layer (the metal layer) is actually the data layer but it almost never is. The data layer itself is polycarbonate, sandwiched between the reflective layers and more polycarbonate layers.
The newer discs like blu-ray movies are made with better plastics that should last at least 100 years. Depending on the dye layer of writable and rewritable blu-rays, they should last either at least 25 years or 100 years.
The foil coating usually deteriorates first
On cds, yes. Technology from the 80s, designed in the 70s.
What disc is left? blu ray?
Bluray and uhd bluray are the current standard
The same promises we got with CD then.
Last year I ripped my whole DVD collection.
Blu-Rays were more of a pain because of the format itself; Handbrake itself wouldn't do the job, I had to use MakeMKV to get a huge mkv file then wash it through Handbrake to compress it to an mp4. Not a single one failed.
Movies on DVD, out of ~300 discs, I had a total of 6 fail because the discs are somehow damaged, most were visibly scratched and wouldn't play back in a normal DVD player either.
TV shows on DVD, out of ~150 discs, ~40 of them partially or totally failed, many had visible disc rot. And there was definitely a pattern that boils down to "cheaper discs tended to fail." Older discs from earlier in the format's life proved more reliable, I think because, for example, my copy of Friends was purchased in the mid-2000s relatively early in the "TV shows on DVD for binge watching" era, some 60 discs in total, no failures. Smaller runs of shows that not a lot of people bought that were kind of plunked out on DVD for the nine people that bought them like Kolchak: The Night Stalker or The Greatest American Hero? 50% failure rate. An interesting one is my copy of Stargate SG-1. I own some seasons from an earlier pressing that came in individual standard plastic cases in a cardboard box, you know what I mean? Those were reliable, only one disc failed because of scratches caused by mishandling. I own some seasons from a later re-release in those slimmer 5-discs-in-a-cardboard-foldy-thing, and more than half of those are unplayable due to disc rot.
Meanwhile I have CDs made in the 80's that still play just fine.
They last very long as long as no humidity catches it tho.
Real, good quality, factory-made discs, maybe. Anything else (from bad quality factory stuff to writable discs), not so much. And backups where not done on factory-pressed discs.
Anytime you get to that length, you always have to think about whether or not someone will have a drive to read it, a computer that it works on, and matching programs to decode the data. Think about some of the formats we had in the 70’s and 80’s and how often people actually have that hardware and software in working order now.
Well yea, but it's a matter of funding and business/government desire. 99% of the time the only people who care about accessing things that old are hobbyists and enthusiasts.
If something critical to a fortune 500 company or government was stored on it and they needed it they would have the means to contract out a specialty one off device just to read it (Or contract out to a very pricey data recovery shop)
And software is software, we can still run 70s and 80s software through a myriad of virtualization technologies fairly easily and cheaply.
You want to make some money? Start manufacturing microfiche readers. There was a brief time in the 20th century where microfilm and microfiche was all the rage for archiving and even publishing technical documents, and now there's a lot of data people need for various reasons and no device to retrieve it on because they all got put in a room in the back of a library and got kicked in when someone backed into the room carrying a heavy box.
old family videos? old government data?
its not just for hobby.
That's for future people to figure out
Aren’t most of those emulateable in dos-box or similar programs?
How do you emulate reading from a physical medium?
That’s the only hurdle if you have the software and decoding both of which are emulateable. Which wouldn’t be overly hard to reverse engineer a connector if you have everything else…
Assuming the software isn't lost, then yeah, typically it can be emulated or reverse engineered to work.
The bigger hurdle is the hardware, especially if the encoding of the data was proprietary, meaning that even if you could get a reading without it, you'd still need to figure out how to decode it into useful data