The CD is 30 years old today • Hacker News Board

Re: The CD is 30 years old today

#41

Post by sjwright » Tue, Oct 02, 2012, 6:58 AM UTC

thirdhaf wrote: post #38

stan_rogers wrote: post #35

Earlier quoted context omitted.

44.1KHz is not the output frequency; it's the sampling frequency from which an unambiguous 20KHz signal (of sufficient amplitude) can be reconstructed. So your calculation needs to take into account that the maximum peak resolution is 20Khz (and that 16 bits may not have sufficient amplitude sampling resolution to accurately interpolate the waveform peaks even if their frequency -- their spacing rather than their pos…

Completely agreed about 44.1kHz being a sampling rate. To make the rest of the numbers nicer I'm going to pretend we're talking about 40kHz sampling for the rest of this comment. It's clear that you can't distinguish between a 0-degree phase shifted 20kHz signal and a 0-degree phase shifted 60.0kHz signal (I thought we weren't going to talk about Nyquist here). However by the same token you CAN represent a 90-degree…

But then you have to ask what actually matters, if the final delivery destination of this information is the ear canal of an adult human.

Given the speed of sound through air, how does a ~23usec time offset compare to the involuntary micro-movements of the head of a typical conscious human?

Re: The CD is 30 years old today

#42

Post by sjwright » Tue, Oct 02, 2012, 7:38 AM UTC

msh wrote: post #12

I am sad that the minidisc lost out to the cd :(

No way! The CD is almost everything you could have asked for in a pre-1995 physical distribution medium. Better-than-your-ear sound quality, cheap to manufacture, no moving parts, relatively robust, allowed for very simple playback hardware designs...

MiniDisc had audibly imperfect sound quality. The media has a complex diskette design with moving parts, is less robust, and requires more complex playback hardware. It was a backwards step in every respect except size and writability.

The perfect product given the technology of the time would have been to just squeeze the regular CD format with all 700MB of data into the 8cm "CD3" form factor. Perhaps adding a "long play" mode suitable for audiobooks (e.g. mono 12 bit/32 kHz PCM).

Re: The CD is 30 years old today

#43

Post by bitwize » Tue, Oct 02, 2012, 6:20 PM UTC

sjwright wrote: post #40

dollarpizza wrote: post #20

Earlier quoted context omitted.

invulnerable to dirt and damage Yeah. Who'd'a thought they'd end up being even more perishable, & way more disposable than vinyl....

Compared to vinyl, the CD would have seemed invulnerable to dirt and damage. Even more perishable? What bunkum. Every time you play a vinyl record, you're causing a very small amount of irreparable damage. Whereas I can still retrieve a bit-perfect copy of my 20+ year old CDs, even if the underside is severely scratched. That said, how can you resist the psychological conundrum of knowing that every time you play a r…

That's part of the beauty of vinyl. It makes you appreciate it that much more. It's wabi-sabi, maaaaaaaaaaaaaaan.

Re: The CD is 30 years old today

#44

Post by dollarpizza » Tue, Oct 02, 2012, 6:45 PM UTC

exogen wrote: post #30

dollarpizza wrote: post #20

Earlier quoted context omitted.

invulnerable to dirt and damage Yeah. Who'd'a thought they'd end up being even more perishable, & way more disposable than vinyl....

What about under the same conditions, I wonder? People handle vinyl pretty delicately, but toss around CDs with reckless abandon.

That's because CDs, as everybody knows, just don't deserve any better. Vinyl, meanwhile, practically calls out to be not only protected, but loved.

Re: The CD is 30 years old today

#45

Post by dollarpizza » Tue, Oct 02, 2012, 6:56 PM UTC

sjwright wrote: post #40

dollarpizza wrote: post #20

Earlier quoted context omitted.

invulnerable to dirt and damage Yeah. Who'd'a thought they'd end up being even more perishable, & way more disposable than vinyl....

Compared to vinyl, the CD would have seemed invulnerable to dirt and damage. Even more perishable? What bunkum. Every time you play a vinyl record, you're causing a very small amount of irreparable damage. Whereas I can still retrieve a bit-perfect copy of my 20+ year old CDs, even if the underside is severely scratched. That said, how can you resist the psychological conundrum of knowing that every time you play a r…

What bunkum.

OK, let me qualify: Vinyl (when played on commodity equipment) does, almost unavoidably, suffer mild (or worse) analog degradation. This is why (if you're of a certain age) you'll recall that for high-value purchases, we usually made cold replicas (uh, "tapes") to insure that the "master" got played as infrequently as possible.

CDs, however, not only degrade spontaneously (even when stored "properly"), but the degradation is pretty much "either-or" -- when they do degrade, usually the whole thing is pretty much unplayable (unless you're putting it in a very expensive player).

In any case, from my own extensive experience over the years, item for item, I've had quite a few vinyl records suffer "moderate" deterioration (aftr heavy playing), but virtually all were still playable to some degree. Really - unless you leave them in the back of your car for too long, that's usually the worst that happens.

Meanwhile, an annoyingly high % if CDs simply get scuffed, or are left out in the air too long -- and end up irreparably damaged and unplayable (at least on generic players).

Re: The CD is 30 years old today

#46

Post by sjwright » Wed, Oct 03, 2012, 8:36 AM UTC

dollarpizza wrote: post #45

sjwright wrote: post #40

Earlier quoted context omitted.

Compared to vinyl, the CD would have seemed invulnerable to dirt and damage. Even more perishable? What bunkum. Every time you play a vinyl record, you're causing a very small amount of irreparable damage. Whereas I can still retrieve a bit-perfect copy of my 20+ year old CDs, even if the underside is severely scratched. That said, how can you resist the psychological conundrum of knowing that every time you play a r…

What bunkum. OK, let me qualify: Vinyl (when played on commodity equipment) does, almost unavoidably, suffer mild (or worse) analog degradation. This is why (if you're of a certain age) you'll recall that for high-value purchases, we usually made cold replicas (uh, "tapes") to insure that the "master" got played as infrequently as possible. CDs, however, not only degrade spontaneously (even when stored "properly"), b…

What bunkum.

Other than some exceptionally rare examples of "bit rot" where errors in manufacturing cause the chemical composition of the plastics prematurely deteriorate, a compact disc will survive at least 50 if not 100 or more years, even with the most exceptionally modest storage and handling conditions.

A scuffed CD is often perfectly playable, and can otherwise be polished back to near-perfect playability with toothpaste and/or ultra-fine sandpapers.

Re: The CD is 30 years old today

#47

Post by msh » Wed, Oct 03, 2012, 10:45 AM UTC

sjwright wrote: post #42

msh wrote: post #12

I am sad that the minidisc lost out to the cd :(

No way! The CD is almost everything you could have asked for in a pre-1995 physical distribution medium. Better-than-your-ear sound quality, cheap to manufacture, no moving parts, relatively robust, allowed for very simple playback hardware designs... MiniDisc had audibly imperfect sound quality. The media has a complex diskette design with moving parts, is less robust, and requires more complex playback hardware. It…

The cd was bad when moving, skipping due to bump was a big issues.