Talk:CD-ROM

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[edit] Spelling

No, it looks like "disk" is right. At least American Heritage Dictionary Fourth Edition says so, and I trust them.

Entry at http://www.bartleby.com/61/16/C0521600.html , and the discussion is pretty interesting.

[edit] Formats

Hi-Sierra and Joliet are top-tier formats for cd and ISO images.

Hi-Sierra and Joliet? What are they? How about the various formats of CD images, ISO, BIN etc? I am aware of these things, but not there exact meaning, so any informed addtion would be useful. Rich Farmbrough 10:04, 15 Dec 2004 (UTC)

High Sierra is the predecessor to the ISO-9660 filesystem (there are only a few minor differences between them).

Joliet is a Microsoft-developed extension to the ISO-9660 filesystem which addresses filename length, directory length, and wide character (16-bit) limitations. See the following:

[1]


The term "ISO" generally refers to a CD-ROM image file, typically used for interim storage of CD-ROM-destined content, generally in ISO-9660 filesystem format (or one of its derivatives). ISO images are sometimes temporarily created by filesystem creation software (mkisofs on Linux), but are commonly used to transfer full CD-ROM images from computer to computer.


Other formats like Ahead Software's Nero (.nrg) formats are essentially proprietary and likely contain additional metadata and features specific to the software.

[edit] CDROMs for the deaf?

We need a disambuigation thing for the Recorder ID / RID, but that means that we actually need an article on the recorder ID..

(Personally, I have not heard about this attempt at big brother)..

--Eptalon 22:52, 23 Mar 2005 (UTC)


[edit] Form factor

Is it just a coincidence that the CD was invented with a form factor such that their drives could be the same physical size as those of the earlier 5 1/4 floppy disks? If not, then this would mean that the inventors of the CD had it in mind all along that they might be used in PCs. Either way, there should be some discussion of this here and in the main CD article...

--4.245.5.118 23:17, 25 Apr 2005 (UTC)

It's just a happy coincidence. According to Kees A. Schouhamer Immink, the size of the CD was chosen based on the cassette tape, i.e. the CD diameter would be about the same as the cassette width. Not because there was any advantage to it, but simply because the cassette was a success. Mirror Vax 08:31, 9 May 2005 (UTC)

[edit] Those magnificient bulky CD-ROMs

I see that this topic does not cover those CDROMs of yesteryears that came in special "protective" tray for each CD and could be accessed only by a special CD-ROM drive where any CD had to be inserted into a blank tray. These were initially introduced as a sturdy alternative. I just don't remember their names and can't seem to find it on the net either. So if anyone knows their name, please go ahead and include that piece of history. It's surprising that Wikipedia does not mention this and I thought most of the users around here were computer buffs.--Idleguy 14:16, July 22, 2005 (UTC)

I don't remember any CDs that had to be used with one of those drives. Rather, there were drives that required discs to be put in a "CD caddy" because they didn't have trays or regular slot loaders, and I guess some discs might have come with their own caddies. It's still a regular CD inside the caddy, though. Mr2001 16:15, 22 July 2005 (UTC)
OK. Thx. Maybe I'll add a word on that in the article. --Idleguy 05:50, July 23, 2005 (UTC)
This is interesting. I've never seen that before. Does anyone have a picture? --Mmartins 08:04, 15 August 2005 (UTC)
Simply typing cd caddy into images.google gives a view results, this one here looks nice: http://www.pc-911.com/product_images/cd_caddy.jpg
You can press the 'buttons' in the lower left and right to open it up to pickup the CD from the inside and the metal-shutter slides away like on 3.5" floppy disk, so its basically like a normal CD case crossed with a 3.5" floppy disk. Only know those things from the time where CD where single speed and a few early CD writers had them two. Heard that BluRay might use them too, however not sure about that. -- Grumbel 23:52, 18 October 2005 (UTC)
A quote from the article:
"...whereas caddy owners could still play loose CDs by loading them into an openable cartridge which was then inserted into the drive (this of course defeated their entire purpose and was more fiddly than loading a disc into an ordinary drive)."
I don't see the defeating-of-purpose here. Just put the CD in the caddy and leave it there forever, right? --67.172.99.160 19:44, 26 December 2005 (UTC)
Then you'd need to buy a new reusable caddy for every disc you owned...
The problem was, most people didn't buy more than the one or two caddies that came with their drive, and just swapped the disc every time. Normally, you should by a pile, and put your frequently used CD-ROMs in the caddies, leaving one or two empty caddies for all other discs. 66.114.93.6 04:03, 12 January 2007 (UTC)
I remember an early form of DVD Burner that worked like that. Seano1 18:34, 10 May 2006 (UTC)

[edit] CD-ROM size

I am confused. If 100 MB = 95.4 MiB, why is a "700MB" CD-ROM 703.1 MiB? --Byronknoll 05:39, 19 December 2005 (UTC)

I added the following text to the Capacity section: "CD capacities are always given in binary units. A "700 MB" CD has a nominal capacity of about 700 MiB. But DVD capacities are given in decimal units. A "4.7 GB" DVD has a nominal capacity of about 4.38 GiB." --Byronknoll 04:19, 30 December 2005 (UTC)

[edit] CD-Rom Mass Production

I often ask "How are CD-Roms made?" and people invariable answer "They are pressed!" but then cannot elaborate. Google'd the top a little but could not find much in the way of results. Can anyone add something to describe the manufacturing process?


They are more like "stamped", because the process happens pretty fast. 66.114.93.6 03:58, 12 January 2007 (UTC)

They are injection-molded polycarbonate. The mold cavity is closed, the poly is injected, and the cavity is cooled briefly before opening. In the early days, molds closed for as much as 30 seconds per disc, maybe more. Modern molding machines can spit out a disc every 3 seconds or so. [2]

[edit] cd-rom disk

don't call it a cd-rom disk. CD already stands for compact disc

[edit] 1 and 0 encoding

Regarding this sentence;

The light/dark and dark/light (pit edge) transitions are translated into 1 bits, the areas with no transitions are translated into 0 bits

Where did this come from? On what level is it supposed to be true? It might apply at the 8-14 encoding level, but it's pretty misleading in that one might read it and reasonably assume that it applied to the file information read off the disk, when in fact there are many layers of encoding between the file information and the bottom (8-14) encoding. Fourohfour 21:01, 4 April 2006 (UTC)

At the lowest level, the eight-to-fourteen modulation is based upon run length encoding of 3 to 11. No pit edges may occur closer then three clock ticks, nor greater than 11 clock ticks apart, and the channel's native frequency (4.3218MHz for CD playback at 1X speed). The EFM employs NRZI, which encodes pit-to-land and land-to-pit transitions as ones in the EFM bit pattern stream. You are correct that there are several layers of encoding and error correction on top of this foundation (CIRC, layered error correction for CD-ROM, etc).

[edit] "To put the CD-ROM's storage capacity into context ... "

The whole section describing the size of a CD-ROM in terms of novels seems unencyclopedic, and does not really add any useful information to the article. Anyone wishing to contextualize the size of a CD-Rom can do so themselves with readily available data. Furthermore, the novel example is not based on actual data (such as the actual size of the average novel) but rather on mere conjecture. The section should be removed unless it can be enhanced to add value to the article in an encyclopedic manner. 199.74.100.30 17:45, 28 April 2006 (UTC)

Perhaps you are right that the figures for the novel given should be backed up a little more strongly. However, as an example, it has a purpose. Sure, people could "work out" such stuff for themselves given the information (assuming they have reasonable intelligence), but why should they have to? We could reduce and remove lots of stuff from various articles on the basis that people could derive the omitted facts from the remaining information, but how quick or easy would this be? An encyclopedia article does not have to be dry and pared down to the bare minimum to fulfil its purpose. Fourohfour 19:30, 6 May 2006 (UTC)
I agree that information like this is indeed useful in an encyclopaedia. The 14th Britannica article on protoplasm, for example, says of a creature that it is 'about the size of a shilling-piece'; ho ho.
But I'd like to tighten it up a bit - words are not 10 letters on average, and the average novel is more than a centimetre. John Wheater 11:03, 21 February 2007 (UTC)
I think it is very appropriate to tell readers in simple vivid terms how much plain-text info a CD can hold compared to ordinary plain-text books -- to very clearly make the point that the volumetric efficiency is greater by orders of magnitude, and so is the economic/materials efficiency. The details of how this comparison is made are not important -- if anyone thinks they have a better way to make this basic point, please suggest it here for everyone to consider. -69.87.204.244 14:44, 6 March 2007 (UTC)

[edit] Speed

I think there was 16x speed too, wasnt there? I dont see it on the list, maybe someone could add it...

I (still) have a 24x, which is not on the list either. It could be that the list wasn't meant to list every speed known to man? 66.114.93.6 04:08, 12 January 2007 (UTC)

The transfer speed section has a confusion between Megabits and Mebibits. I can not correct it as I do not know if the 1x speed is 150x1000 bytes/second or 150x1024 bytes/second.


The speeds are implementation-dependent, and vary from manufacturer to manufacturer, model to model. It's largely irrelevant for CD-ROM at this point, but there have been 1X, 2X, 3X, 4X, 4.5X, 6X, 8X, 10X, 12X, 16X, 20X, 24X, 32X, 48X, 52X, and probably others (including, of course, all the partial-CAV and CAV speeds). I wouldn't bother listing all the speeds.

1X (Real-time) in CD equates to 75 sectors per second; for CD-ROM Mode 1 tracks, this is 75 sectors per second * 2048 bytes user data per sector = 153,600 bytes per second.

[edit] First computer CD-ROM

I've read in some portuguese articles that the first computer in the world to have a CD-ROM was an MSX home-computer made by Philips. This information would be very important to this article provided it is true. Could someone find more information about it? Regards Loudenvier 16:51, 12 September 2006 (UTC)

I can't answer your question - but I CAN give you some other history that you might find interesting.
I actually worked on the team at Philips Research Labs (in Redhill, Surrey UK) who produced the first ever working CD-ROM.
We took a very early Philips audio CD drive and modified it to connect up to a 68000-based 'home computer' research prototype called 'C.H.R.I.S' which we'd designed and built in-house. The first ever CD-ROM disk was pressed on the Philips audio disk production line and just 50 of them were made. The huge capacity of the CD-ROM was a bit of a challenge for us because our biggest hard drives were only 20Mbytes and the CD-ROM could hold 600Mbytes or so. We quite simply had no way to author 600Mbytes of data. Data went to the audio disk factory on VAX-formatted 9 track magnetic tape - but we needed random-access to stand a chance of getting this together. We decided that a good application to try would be a dictionary - but we quickly realised that this would be a massive data-gathering exercise - so for research purposes we decided to do just one letter (we chose 'O' - for reasons now lost to history)...it was still an insane amount of work. The idea was to have word definitions (including links much like Wikipedia's), synonyms and antonyms, images (where apppropriate) and audio samples for pronunciation.
My job as a junior engineer was to write a paint program for an artist to use to paint the pictures. Remember, this was in an era before you could buy paint software (except in specialised systems for TV production houses) - this was also before the invention of the mouse. My paint program used a digitizing tablet but I believe the demonstration system for the CD-ROM used a touch-screen.
We employed a contract artist (who'd never sat in front of a computer in his life) come in and learn how to draw using my software. He painted an Oaf (our favorite image), and Oak apple, an Oak leaf and an Oak tree...and a bunch of other things beginning with 'O'...and much, much later...an Oyster. Our office secretary (who had a very nice speaking voice and a 'posh' English accent) read out all of the words (it took her a LONG time!) and the entire team took turns to type in the text (which took FOREVER). 100% of the software was custom-written for the demo - the entire C.H.R.I.S operating system - everything. I recall that David Penna wrote the bulk of the demo software - including some nice features like antialiased fonts which were way ahead of their time. Everything was written in C.
As I recall, most of the 50 disks we pressed worked - and 50 more were later pressed with more pictures, etc. As far as I know, none of those original disks survived (what I wouldn't give to have one of those!). The system was taken to a variety of trade shows and shown off to visitors to the research labs on dozens of occasions. Eventually, the team moved on to look into 3D graphics (my part) and into CD-ROM standards and authoring tools. Originally, we anticipated software on CD-ROM being interpreted from some kind of intermediate code rather than being raw machine-code because we believed that CD-ROM 'players' would be stand-alone machines connected to TV sets that would contain a variety of CPU types. This never really took off because the PC revolution hit us and pretty much all of the cool standards we drew up were blown away in favor of the (lame) "just like an MS-DOS file system" that we're stuck with to this day.
Whilst the audio CD was a joint effort between Philips and Sony - I don't recall who put the first CD-ROM drive into a production computer. We certainly made a variety of home computers - and we did make an MSX machine - so your suggestion is quite plausible. But I really don't know for sure.
SteveBaker 20:53, 29 September 2006 (UTC)
Steve, could you add a date to this information, which I'd like to see in an article. John Wheater 10:49, 21 February 2007 (UTC)
You mean a date to when the work was done? I'm not sure precisely. We started on it before the first Philips audio CD player hit the market - but not long before - so it would have had to be 1981 or 1982 or so - but I'm not 100% sure. However, I don't think you should write an article based solely on what a fellow Wikipedian says in a Talk area. You need references that other people can check - and frankly, I don't have any or I would have written the article myself. SteveBaker 13:51, 21 February 2007 (UTC)
I too don't think I should write this article! Indeed it never crossed my mind to do so. But, ahem, I think maybe you should, some time in the next forty years or so. The thing is, your narrative is what historians call a primary source. When Niels Bohr wrote his article on the atom for the 14th Britannica, he spoke from his own knowledge; CD-ROM history is less important, but worth having on record. And firsts are an important element of history. Maybe what is needed is not an article, but a history section in this article, as a third-person detached narrative, naming those involved, citing 'personal knowledge of Steve Baker' as the reference - the sole reference if there really is nothing else, though surely the Philips records must show something. And then someone would chip in a bit of Sony history, and so we'd wiki on into the sunset... John Wheater 16:28, 21 February 2007 (UTC)

[edit] Longevity

I think it would real nice if some info about the longevity of CD-ROM for long term archiving is included in the article : Jebrennan 03:27, 7 December 2006 (UTC)

It's a fairly controversial subject. Some CD's (not really CD-ROMs necessarily) were made with some kind of cheaper aluminium layer. If there was even the tiniest pinhole in the layer of aluminium, it would slowly grow by a weird process something akin to surface-tension in liquids) until it covered enough area to cause a mis-read. If there were sufficiently few of them, the CD's error correction processing would repair the data stream - but this only works if the hole doesn't grow too big - if the holes are not positioned fortuitously - and if there are not also too many surface scratches. Eventually there are too many errors and the error correction system would be overwhelmed.
But it's hard to place a definite lifetime on the CD because so much depends on where the holes are - how old the disk is - and how much usage it has had. I've had disks from that era fail in less than a year. Once the problem became really well known, most of the fabrication plants tweaked their processes to eliminate the problem - so I doubt that modern CD's suffer from the problem. Aside from that issue, a CD that's left in storage in a dark place - propped up on it's side and supported by the center hole - should have an enormously long shelf life. I don't think an upper limit has ever been established. The very first audio CDs I ever bought still play just fine (Dire Straits "Brothers in Arms", some Glen Miller and some Bach fugues), Those were bought on the first day that consumer CD players and disks went on sale - only to Philips employees and only in our "Staff Shop"). Those are probably amongst the oldest mass-produced consumer-grade CD's in existance and they still play just fine.
Recordable disks are a different matter - they work totally differently from mass-produced disks - I have no idea how long they might be expected to last.
SteveBaker 23:36, 28 January 2007 (UTC)

[edit] File Name Length

When burning a CD, the CD format seems to limit the length of file names. If someone knows the rules, it would be great to have it here. Also, there seems to be a limit to the number of characters in the title of a CD too. Thanks. Jebrennan 03:27, 7 December 2006 (UTC)

No need to clutter up the CD-ROM article with that kind of information, while it is available in the correct articles: Universal Disk Format, ISO 9660, Joliet (file system). Note that there's no such thing as a "CD format", but in fact more than one CD-ROM file system.
On a personal note, if you feel the file naming is too limited for your purposes, I'd suggest you use a better CD/DVD authoring software that supports UDF (IMHO, ISO9660 and Joliet are outdated and should only be used when you have to -> on old players or operating system.)--87.122.52.27 16:43, 23 January 2007 (UTC)

[edit] When was the first cd rom produced? What about the history of adoption of the format?

Trollderella 08:13, 14 December 2006 (UTC)

Scroll up a bit and read my comments under "First computer CD-ROM" - I actually worked in the group who produced the first ever CD-ROM. Sadly, I can't write about it for the article because that would be OR. SteveBaker 23:11, 28 January 2007 (UTC)

[edit] Read-only "media"

“ It is also debated whether the correct terminology is read-only memory or media. It is generally accepted that, in technical terms, media is the correct terminology. However, due to the widespread use of ROM to refer to other devices such as EEPROM and Flash-ROM (where memory is the correct terminology) most people define CD-ROM as also being memory as it sounds like the abbreviation is from the same origin. ”

I have removed this unreferenced and rather weaselly and spurious assertion (and other mentions of it) from the article. Plugging the term "compact disc read-only media" into Google returns a piffling 72 unique results, compared to 232,000 for "...memory". This suggests the "media" interpretation of the acronym is far from "generally accepted". FOLDOC, OED and Webster's all agree "memory" is the correct term. ~Matticus TC 20:16, 28 January 2007 (UTC)

(As I've said previously - I worked on the team that made the first CD-ROM). The term 'ROM' - meaning "Read Only Memory" was in common use a decade before we came up with the CD-ROM. There were already lots of kinds of ROM - 'PROM', 'EPROM', etc. The name 'CD-ROM' came about in the obvious way - from taking the name of the audio disk "CD" and tacking on "ROM". So it's definitely 'Memory' and not 'Media'. SteveBaker 23:18, 28 January 2007 (UTC)

Like many things, popular acceptance has asserted one over the other, so the number of links on Google isn't really a valid measure of 'correctness' in this sense (especially as the Google algorithm will naturally lean towards the currently indexed pages). I do however accept Steve Baker's comment and defer to his closer knowledge on this subject. Having said that, I worked in PC hardware when the CD-ROM was released and had an intimate knowledge of the market and the coverage in press. Whilst most of those paper-based arcticles have no on-line archives going back that many years (there is no call for them), I do not think it valid to ignore the large number of people who, at the time, believed (rightly or wrongly) that 'media' was the more correct definition. I did endeavour to reference my original statement, but as already pointed out, widespread use of the 'memory' acronym has rendered the 'media' use somewhat outdated. As you will notice, Steve also agrees with my statement that the reason the 'memory' was chosen/accepted was because of the widespread existing use of other 'ROMs'. My proposal is to rewrite my original statement in a more 'neutral' manner indicating that the debate is now somewhat moot because of the general acceptance of 'memory'. This should ensure it is not open to being interpreted as weaselly. Please enter comments on the subject here and I will endeavour to post at some point in the next few days. DanMatthewsUK 12:48, 16 February 2007 (UTC)

Duly amended as per my statement above. DanMatthewsUK

[edit] How is the rate of 150 kB/s calculated?

How is the 1x rate of 150 kilobytes pre second calculated? Is the unit SI base 1,000 or base 1,024? —Dispenser 01:18, 19 February 2007 (UTC)

[edit] recording at high speed

"Recording data CDs at very high speed (40x) can be done without losing information. However, if done the same with PlayStation or Audio CD it will result in an unreadable PlayStation disc or an audio CD with lots of clicks because there are no error correction codes and the errors are more likely to occur at high speed recording."

After the first sentence, this paragraph from the current article sounds kind of stupid. It should be deleted or re-written by someone who knows what they are talking about and knows how to write well. -69.87.204.244 14:31, 6 March 2007 (UTC)

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