Talk:Compact Disc/Archive 1

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Contents

See Also Section

I think the see also section is way too long. The linklist should be trimmed to a more managble size. I can take a look but other people should as well. Chipotlehero 16:02, 2 August 2007 (UTC)

800 MB, 90 Minute CDs?

This article asserts in several places that the capacity of a CD is 700 MB (or 80 Minutes of audio) - here in Britain, at least, 800 MB / 90 Minute CD-Rs are readily available - is this article wrong, or missing some information to clarify this discrepancy? --Zik-Zak 09:57, 1 November 2006 (UTC)

They exist as do even large 99 minuite ones but i'm pretty sure they violate the spec, also they go over the limit of the CD-R atip data spec so you have to use overburn options if you want to use the whole capacity. They are already mentioned over at CD-R but i don't think they are widespread enough (you don't see them in regular computer shops only places that specialise in CD media) to mention in the main CD article. Plugwash 02:57, 25 February 2007 (UTC)
For 90 and 99 minute CD-R, the ATIP has the correct time encoded in it. Going over the time value encoded in the ATIP is overburning. 90 and 99 minute CD-R discs aren't available in the USA on any store shelves I've seen.

99 Tracks?

I got to this article from this page, which mentions that CDs are limited to 99 tracks. But I can't find that fact anywhere on this page. I suspect it's true, but I hate to add it without actually knowing it for certain. Would someone that can verify that fact add it somewhere? Thanks. Rmarquet 00:16, 18 October 2006 (UTC)

If nothing else, the typical CD player cannot display a number larger than that.—überRegenbogen 02:48, 26 February 2007 (UTC)

Who's the fool who wrote this?

"equivalent to approximately 500 rpm at the inside of the disc, and approximately 200 rpm at the outside edge." That would mean that the inside is spinning more times than the outside in a given timeframe, creating a spiral. Physically impossible, and yet it's in the main section of the wiki.

Please sign your comments using four tildes (~~~~) and please take a look at WP:CIVIL. In this case, the misunderstanding is yours. The article states that CDs are read at constant linear velocity, which logically requires a disc to spin more rapidly when it is being read near the center than when it is being read closer to the edge, where the circumference is greater. It does not say that it turns at these two rotational speeds at the same time.  ProhibitOnions  (T) 10:45, 15 October 2006 (UTC)
Also, headings should betray the content of the section. ツ —The preceding unsigned comment was added by Brian Patrie (talk • contribs) 05:58, 26 February 2007 (UTC).

This article is a complete mess!

Somebody needs to go through and fix the dozens of grammatical errors and cases of redundancy. Theswillman 15:40, 3 June 2006 (UTC)

  • Oh, yeah? In that case, you are welcome to help. Along with all the other people who leave such messages on talk pages. vLaDsINgEr 02:15, 17 May 2007 (UTC)

First albums?

What were the first album(s) released on cd, overall and in the USA? ---Scaryice 10:02, 9 August 2005 (UTC)

Speed notation and capacity

I hope to see the 1X unit of CD throughput defined here some day, also the 1X of DVD defined there. I'm guessing the "Google define: 1X" claims of 1X CD = 150,000 byte/s and 1X DVD = 1,380,000 byte/s are slightly incorrect, because seemingly imprecise, because rounded decimally. (Pat LaVarre, 21st September 2004)

CD audio has 176,400 bytes a second of data to be precise (44100 * 2 bytes (16 bits) * 2 channels (stereo)). The error correction overhead for a data CD is roughly 13% (derived by the number of bytes of data an 80 minute CD fits compared to the number of bytes of audio data if burned as an audio CD), so we get 153,333 bytes a second. Samboy 02:03, 10 Nov 2004 (UTC)
A CD sector has 2352 bytes (not counting elementary synchronization and error-correction info). In typical CD-ROM modes, 2048 bytes are used for data, the rest for error correction. You'll note that one second of audio data is stored in exactly 75 sectors, so the data transmission rate "1x" for CD-ROM data in typical modes is 75 * 2048 = 153,600 bytes per second. I'm saying typical modes because it's possible to use more or less than 2048 data bytes per sector, resulting in a different trade-off of capacity and speed vs. reliability. Aragorn2 12:07, 26 January 2006 (UTC)
CD (according to the article) can hold 650 MB or 74 minutes. So assuming that a cd drive can read 650 MB in 74 minutes at 1x, the 1x read speed of a 650MB data CD is 650MB / 74 min = 650MB / (74 x 60 sec.) = 146,396 B/s = 1.17 Mbit/s. If by MB the article was referring to 1024 KB (the article is unclear on this!), then multiplying by 1.024 x 1.024, the modified figures are 153,508 B/s = 1.23 Mbit/s. --Tokek 03:58, 29 Mar 2005 (UTC)


650MB is the capacity for data mode, which has more redundancy than audio mode. VCDs and audio CDs are written without the added redundancy, and have a max size of about 735MB on a "650MB" CD. So on a data CD, you're actually reading in the redundancy data along with the user data, which creates the 13% of overhead in Samboy's derivation. (I believe MB in this case does refer to the powers of two variety. Are we ever going to start using "Mebibyte"?) - mako 01:05, 30 Mar 2005 (UTC)
Right, audio is (176,400 B/s) * (74mins) = 783,216,000 B, data is 650 MiB = 681,574,400 B, data read speed is (176,400 B/s) * (681,574,400 B / 783,216,000 B) = 153,508 B/s = 1.228 Mbit/s. Different calculations (both took overhead into account btw), same results. --Tokek 07:16, 30 Mar 2005 (UTC)
I just wanted to point out that the CD drive reads in the same amount of raw data at 1x for audio as well as data. Perhaps the article could benefit from an overview of effective sector sizes in different data modes. - mako 21:13, 30 Mar 2005 (UTC)
Good work, but all this probably belongs on the CD-ROM page. --Dtcdthingy 00:40, 31 Mar 2005 (UTC)

Are we ever going to start using "Mebibyte"?

A vote has been started on whether Wikipedia should use these prefixes all the time, only in highly technical contexts, or never. - Omegatron 14:59, July 12, 2005 (UTC)
How about for articles on computer technology from before the (rather silly mebi/kibi etc retcon IMHO) "new wave" prefixes were invented, stick with the usage contemporary to the technology? Editing an article on the apple ][ to say it had 64 kibibytes of RAM is anachronistic, eh? Anyone who grew up with computers during the boomtime years of the lates 70's and 80's knows *exactly* what kilobyte, megabyte etc mean. They ARE NOT CONFUSED by them because they learned those numbers in school, in computer classes and from the people who invented digital electronics- who are the people who coined the original terms. Kibibyte etc is a slap to the faces of computer pioneers! "We know better and we're going to change these terms!"

I was under the impression 24 bit audio was in use, and I know higher mastering rates are used. Please explain how this relates to the cd (I know hard drives arent' limited for bit rate and are used for storage, is the cdabsolutely limited for bitrate in consumer audio?). thank you for sharing you knowledge!--Tednor 10:43, 5 December 2006 (UTC)

Audio CDs are and always have been 16 bit stereo at 44.1khz, no more and no less. A data CD can of course contain any format you like subject to capacity limitations.
Production is done in higher bit depths and frequencies than the final product in order to reduce the buildup of errors and artifacts. Plugwash 17:54, 5 December 2006 (UTC)
AFAIK, There is provision in the format for 1 and 4 channel, but it is rarely—if ever—used. And it would not surprise me if there are players that would grossly mishandle anything other than stereo. —überRegenbogen 05:40, 26 February 2007 (UTC)


Well doesn't "dithering" in itself introduce artifacts and require something called "noise shaping" and what the hell is "triangular distribution" anyway?

A 120mm disc can store about 74 minutes of music or about 650 megabytes of data.

Is it true that 74 minutes length was decided to have enough room for Beethoven's 9th symphony? I couldn't find any definitive reference.
Yes. The president of Sony at the time (some Japanenese guy whose name eludes me at the moment) was a huge Beethoven fan. He wanted the compact disc to be big enough to hold Beethoven's 9th symphony its entirety (so that he wouldn't have to change the disc), so he basically demanded that the engineers make it hold 74 minutes. →Raul654 03:23, Jul 1, 2004 (UTC)
There is a lot of urban legends about this entire thing, so I will point people to this page. The general impression I get is that, yes, the length of Beethoven's 9th did increase the diameter by one centimeter so that a CD could fit all fo the 9th (which usually doesn't need 74 minutes, but needs more than 60 minutes, which is how much time we would have gotten if we didn't increase the diameter by a centimeter). Samboy 01:57, 10 Nov 2004 (UTC)
Actually, you're wrong. The length of time is a function of the diameter of the CD. From http://www.exp-math.uni-essen.de/~immink/pdf/cdstory.pdf it can be seen that the diameter was derived from the diagonal length of the 1962 Cassette (11.5cm, +0.5cm due to a Phillip's executive decision).

dates

History, please! When was the CD created, 1983? CD-R, early 1990s? And the CD-RW? And how about a link to a more generic entry on data storage? Further, how did the engineers decide on the diameter? Was it to match the 5.25" floppy disks common in the early 1980s? Or was it to have enough room for an hour of music or for Beethoven's 9th Symphony?

Please see above, I just answered this question. (10/10/06)

The CD was created in 1979. It was introduced to the U.S. in 1982. The first CD recorder was made by Yamaha and imported to the U.S. in 1988 (I was working for the company that imported it). CD-RW didn't come into being until about 1996.

disc vs disk

In my opinion, the discussion about disc vs. disk is a moot point because "compact disc" is a tradename not a generic name.

What is with the disc vs. disk anyway? I have always used disk for a disk and disc when referring to something round. My spell checker seems to say that they can be both used for a tech disk though, odd. --Josquius 16:58, 20 May 2004 (UTC)

You're right - despite what any dictionary says, the inventors of teh compact disc named it disc. It's a brand name. You don't accept "cleanex" as a correct spelling for "Kleenex", or "zerocks" for "Xerox". Disc it is disc it always has been, and disc it always shall be. Don't believe me, go look at the logo. It's on every CD jewel case.

The Philips trademark may spell it "disc", but that's not itself definitive as to general usage. The current article text is needlessly prescriptive; newspaper style guides are poor sources on such matters, since their purpose is internal consistency, not to determine the "only correct usage". If a section like this is even appropriate, better that it mention the trademark and the history, not seek to provide "usage notes" as the current text does. Alai 03:25, 20 Mar 2005 (UTC)
It goes to show that some people consider the correct spelling to be very important. And from what I've seen, it's always been disc with a "c". I do agree that quoting the entire style guide entry is unnecessary; a small mention is sufficient. - mako 08:26, 21 Mar 2005 (UTC)

I have tended to see disc used for optical formats and disk for magnetic; where people distinguish between the two. However the OED only has the following to say on the matter:

The earlier and better spelling is disk, but disc is now the more usual form in British English, except in sense 2g, where disk is commoner as a result of US influence.

FOLDOC more or less agrees. belg4mit 2005-11-21

Although the general consensus seems to be that both terms (disc and disk) are acceptable, would it be possible to have some kind of consistency within this article? It does seem to change from one to other quite a bit? I would suggest using 'disc' thoughout (when refering to a CD) simply for a smoother flow. Either way, when the word 'compact' precedes it, it should be 'disc' in view of the reference being to the product rather than its use. Interestingly, I understand that the term 'disc' was in use for gramaphone records long before the launch of the CD.

Bill Gates?

The CD-ROM was pushed by Bill Gates? This needs a bit more info! - David Gerard 13:09, Jan 13, 2004 (UTC)

See Bill Gates Mikkalai 04:35, 27 Jan 2004 (UTC)

Storage Capacity

The advantage of MP3 is that it increases CD storage capacity by up to ten times without significant degradation in sound quality.

That statement is patently false. MP3 does not affect CD storage capacity at all. However, at 128kb/s, MP3 is very roughly 10× smaller than CD-audio and that is why you can fit 10× as many songs in MP3 as in CD-audio.--NRen2k5 16:25, 30 August 2006 (UTC)
That's likely to get an argument from some audiophiles! --Charles A. L. 16:46, Feb 15, 2004 (UTC)
Not to be pedantic, bu the statement is wrong in itself as well: the storage capacity is still the same (650 Mb of wav or 650 Mb of mp3 is still 650 Mb)

The statement is NOT wrong! What you have failed to notice is that cd's can store 80 minutes of music or HOURS of music, so the statement is correct if one is measuring minutes of music. Where it went wrong was in not defining what was being measured, but it is not patently false.--207.69.138.8 15:50, 7 December 2006 (UTC)

How about this: "Since MP3 files are much smaller, ten times more music can fit on a CD without significant degradation in sound quality ." --Calan 16:26, 18 December 2006 (UTC)
I have to take exception to "without significant degradation in sound quality". This is at best, highly debatable. At the cited level of compression significant loss above 16kHz occurs. Subjective remarks should be qualified. e.g. "Since MP3 audio is much more compact than PCM audio, much more audio can be fit on a disc (up to about 85 times as much, depending upon the quality needed—about 10 times for music, at quality acceptable to many listeners)." —überRegenbogen 06:30, 26 February 2007 (UTC)

Intro

That intro is a tangled mess and not at all a good encapsulated summary of what a CD is and is for - the sort of thing that would make a useful concise article in itself. Anyone want to try a rewrite? - David Gerard 16:08, Mar 10, 2004 (UTC)

Hardware photos

Hmm, the business-end of the CD is not depicted in a photo yet. Kim Bruning 14:09, 5 Apr 2004 (UTC)

I'm about to buy a digital camera ... mind you, I'll be on holiday with it for three weeks! Anyone? Anyone? - David Gerard 14:18, Apr 5, 2004 (UTC)
Interwiki rules:
http://nl.wikipedia.org/wiki/Afbeelding:CompactDisc.jpg
have a nice day :-)

Writable drives

For drives installed in computers, all current CD-ROM and DVD-ROM drives can read and write CD-R and CD-RW discs.

This is nonsense. ALL is VERY false. Recordable drives are almost never called ROM drives. This implies that no more CD-ROM or DVD-ROM drives are made. Only CD-RW drives, DVD-ROM/CD-RW combo drives, Or DVD+/-R(W) (also DVD-ram) drives are made. Therefore I have removed this Statement from the main page. Feel free to correct it and place it back on the page. Tacvek 22:55, 15 Jun 2004 (UTC)
Statement was poorly clairfied. Windows operating system itself calls all such drives ROM's, so this person isn't too far off. To propose that no cd read only's are manufactured is a stretch though. The truth is that the overwhelming majority of newly marketed drives will at minimum write to a CDR/RW.--207.69.138.8 15:50, 7 December 2006 (UTC)

Velocity specs

I realize that CDs are constant linear velocity, but what are the general maximum and minimum speeds for reading at 1X (CD audio)? Ckape 22:46, 22 Sep 2004 (UTC)

Red book standard is 125cm/sec with +-5 cm/sec tolerance. Thus the recording can be made to spin at track speed 120-130 cm/sec and CD-players have to be able to adust their speed accordingly. As the manufacturing process has matured it has become possible to use the red book tolerance values to an advantage by making the pits as small as possible, putting the traks closer to each other and making the disk spin as slow as possible, all within the red book tolerances. With these tweaks we can get more than 80 minutes out of 74 minute disk, without breaking Red Book rules. (Petrus)

Possible DMCA Violation?

Quoted from the current version:

Another copy protection method places a data track (usually containing bonus software for computer users) at the end of the disc and gives it an invalid size in the disc's table of contents. This is intended to prevent the data track from being ripped, but can be defeated by ignoring the table of contents and reading the disc sector by sector.

Isn't detailing circumvention measures to a copy protection scheme in violation of the DMCA unless for academic or virus scanning purposes? I'm specifically referring to the line:

but can be defeated by ignoring the table of contents and reading the disc sector by sector.

Could Wikipedia have any liability here?

Probably, but it's something very much worth fighting. The DMCA makes a joke of "Fair Use". Not to mention the part about detailing circumvention measures is clearly unconstitutional. But regardless, Wikipedia is most certainly "academic", so it should not be in violation of the letter of the law to begin with.--NRen2k5 16:36, 30 August 2006 (UTC)
I'm not sure of the exact language of the Dastardly Molestation of Consumers Act. But i think that such a crude "protection" measure (akin to locking a room by laying a 2x4 in front of the door) is beneath the level of its provisions. A user could easily clone a disc for backup (as i have done for some very hard to find discs) without ever noticing that there was any kind of protection mechanism—as easily as a person stepping over the 2x4, without ever knowing that they're meant not to. —überRegenbogen 06:49, 26 February 2007 (UTC)

sampling frequency

Explain why CDs have a sampling frequency of precisely 44.1KHz

I have added the answer to the article:
The reason why the unusual sampling rate of 44.1kHz was chosen was because, at the time the CD specification was being developed, the only way to make a reasonably affordable digital audio recorder was to convert digital audio in to a video signal, which was then recorded to a VCR. A NTSC video signal has 245 lines of resolution, updated 60 times a second; a PAL video signal has 294 lines of resolution, updated 50 lines a second. The technology could store 3 samples in a single horizontal line, either at 14 bits with some error correction, or at 16 bits with almost no error correction. There was a debate over whether to use 14 or 16 bit samples when they designed the compact disc; 16 bits prevailed. Hence, the decision to use the 16-bit, 44.1kHz sampling rate. The Sony PCM-1630, an early CD mastering machine, was just a modified U-Matic VCR Samboy 02:04, 10 Nov 2004 (UTC)
Researching this a littlmore a raw NTSC signal has 525 lines of resolution, updated 30 times a second (the number is different above because of interlacing). Some of this signal is part of the vertical blank, but some of this signal is the invisible part used for storing closed captioning and what not. Everyone says that NTSC has 480 lines of visible resolution, but the people who made those old PCM encoders (mainly Sony) figured out some way to get another ten lines in there somehow. I can't find any details online, but I guess they used part of the signal made invisible for closed captioning purposes and what not. Samboy 13:39, 20 Dec 2004 (UTC)
The vertical sync signal between each field is quite complex, spread out over several lines. I presume 245 is the maximum number of lines that VCRs would reliably record; and that would leave enough room for a reasonably valid sync signal in between that would not confuse a VCR.
The 525 lines figure actually just means 1 line lasts 1/525th of 1/30th of a second, it doesn't account for blanking interval. I guess the 480 lines figure comes from digitizing NTSC video.
Dtcdthingy 19:53, 20 Dec 2004 (UTC)
I think the 480 line figure also comes from people being conservative about the number of scan lines in a NTSC signal that contain actual picture information. The people that say "480 lines" are usually making digital TVs and what not; they mean "480 lines of picture". I found something here which gives us the following numbers (this is for programming those old Atari 2600s):
  • 192 visible lines
  • 30 "overscan" lines (presumably visible to a VCR, but not visible to some TVs) 222 lines so far.
  • 37 "vertical blank" lines. 259 lines so far.
  • 3 lines during the actual vertical sync. 262 lines total. 262 * 2 = 524; this is as close to the 525 number possible because of interlacing.
Now, from this, I get the sense they could have maybe have gotten as many as as 259 lines from a single frame. They grabbed 245 lines; it may be that the rotary heads on the old U-Matic VCRs spun at a speed such that they didn't record during some of the V-Sync signal. The specs for these old VCRs publically released do not tell us how many scan lines they recorded in a second, alas. I looked over at this page and the manuals only discuss horizontal resolution; the big number at the time was how much horizontal resolution you could get; people didn't even think twice about the vertical resolution.
If different numbers of scan lines were chosen, here is the sampling rates we would have had:
  • 240 ("480 lines" resolution): 43.2 kHz
  • 245: 44.1 KHz (this was the one chosen)
  • 250: 45 kHz
  • 255: 45.9 kHz
  • 259: 46.620 kHz (this would have been really pushing it)
Somebody in the 1970s decided that 245 lines in a single frame was the maximum number of scan lines they could safely use and we can only speculate about what factors they considered when making this decision. It's strange that something as universal as the 44.1kHz sampling rate is something whose origins we can't fully track down. And, oh, Merry Christmas! Samboy 12:52, 25 Dec 2004 (UTC)
I assume the "245 lines" thing is per field and not per frame. PAL and NTSC are interlaced video, meaning only every other horizontal line is updated every 1/50 or 1/60 of a second. Nearly all PAL/NTSC-based video recording formats utilise all 480/525 or 576/625 lines per frame - with exceptions of VCD and some early home video tape format that skipped every other field for long-play recording (I forget what it was), nothing reduces the vertical resolution. Also, sometimes I hear NTSC being quoted as having 483 lines of visible video. --Zilog Jones 16:54, 18 Jun 2005 (UTC)
NTSC (RS-170) video has 525½ interlaced lines of picture (525.5i, if you like). Sync does not subtract from this! VBI data does subtract from it—leaving about 490 lines of safe territory. (480 became the standard for NTSCoid digital video, because it was already a common digital resolution.) This translates into 245 safe lines per field. Accepting the above 3 samples per line, we get:
3 × 245 × 60 = 44100 samples per second. ☺
Okay then! Plug that data into the main article. Simple mundane technical limitations dictated the 44.1Khz sampling rate, not any of the technobabble many audiophiles like to recite when asked that question. :)

Size of center hole

THe size of the center hole of the CD is the dutch equivilent of the penny. Phillips developed it there and they needed a size for the center, so I guess that just used a coin. If anyone knows the coin name please add it.

Yes, it appears to be more or less the same size as a Dutch 10 cent coin, which appears to be exactly 15mm. --Zilog Jones 01:29, 13 Jun 2005 (UTC)
Can it be comfirmed there is an actual relation between the two? I've added it to the article for now - previously there was no mention of the hole and its purpose at all so I said some stuff on that too. --Zilog Jones 17:57, 15 Jun 2005 (UTC)
The diameter of CD's center hole is irrelevant for Wikipedia. It has no effect on the playing time, capacity, or other key parameters of the CD and DVD. The possible relationship with the Dutch 10ct coin is coincidental. In the same way as you did, I could write that CD's outer diameter, 12 cm, is the same as that of the Heineken beermat (coaster). And as you may know, Philips and Heineken are Dutch companies! So my conclusion, let us stop listing (unproven) trivialties in wikipedia, so pls remove your contributions regarding the center hole and the Dutch coin. Dsc 14:31, 19 Jun 2005 (UTC)
OK, similarities with the coin have been removed, but the mention of the hole being there is by no means irrelevant - especially in the "physical details" section. It is a vital part to the functioning of the disc. --Zilog Jones 20:58, 20 Jun 2005 (UTC)
I have checked this at Philips Natlab, their R&D centre (my father-in-law works there). They did confirm that the 10 cent coin story is true. During a design meeting the engineers discussed the drive mechanism and one suggested it should be 'no larger than this' while tossing the coin on the table. This was actually used in their test setup and it was carried over during the development cycle. They also confirmed that the 12cm dimension had nothing to do with Beethoven, it was decided together with Sony to have similar physical dimension as a audio cassette tape - they reasoned that one of the failures of the laserdisc was the large size of the disc making it uneasy to carry around.
I added the info earlier but it was removed (because of its' urban legend status) so I asked at the Philips R&D center if they would confirm this. So 10 cent dimension: true, Beethoven: false. Felsir 08:44, 28 September 2005 (UTC)
Great, Felsir, but could you quote somebody directly? It would really help settle this to be able to say something like: "According to audio engineer XXX, who worked on the development of the CD format at Philips from 1979-1982, the size of the center hole...." ProhibitOnions 14:12, 28 September 2005 (UTC)
I'll ask if they recall who actually made the suggestion. They did mention the name of Kees Schouhamer Immink (not sure of spelling) as one of the chief engineers but I don't know if he had part in this particular thing. Felsir 17:41, 28 September 2005 (UTC)
Ah, after rereading the CD article, I noticed that Kees A. Schouhamer Immink even has a wiki article written about him. I'll ask if they can backup the centrehole story with a name. Felsir 17:47, 28 September 2005 (UTC)

Fortunately it has been verified by Felsir's Dutch uncle in law or nephew, who works at Philips' Research: Ohga's Beethoven's Ninth is out, and we agree that CD's outer diameter, 12 cm, is the same as that of the Heineken beermat (coaster). Philips and Heineken are well-known Dutch companies, so at last we agree, and have back up from the great Philips' Research employees! Dsc 19:15, 28 September 2005 (UTC)

My wife's father works at Philips Natlab (which is the R&D center in Eindhoven, the Netherlands) where the CD was co-developed. So it's not a just a Philips R&D department. I don't know where the Heineken beermat story comes from, it has nothing to do with the development of the CD. In fact, the first CD prototype was 11.5 cm in diameter. See [1] (page 3) with Kees Immink's explaination of disc parameters (unfortunately the centerhole is not discussed). I have no reason to doubt the 10 cent coin centerhole story since all the details they told me at Philips Natlab seem to match with info I checked in various documents I found spead across the web.
I understand that the user Dsc either doesn't believe me, or doesn't want the 10 cent coin story in the article (since he/she removed it twice even I provided info on the talk page and the message in this thread stating that the centerhole is irrelevant).
What do other people think, include or not? Felsir 08:13, 29 September 2005 (UTC)

I agree with User:ProhibitOnions, who likes to see a 'real' source, for example, a quotation from a member of the Philips/Sony CD taskforce. May be, Kees Immink. The Internet is an unreliable source, too many copiers. For example, many Internet sources quote the 'true story' of the CD's playing time and Beethoven's Ninth. But according to Kees Immink's 'The CD Story' in [2], we should not believe the Beethoven story. What now? At this moment, the relationship between the center hole and the Dutch coin has the status of a rumor, and should, I think, not be mentioned in the Wikipedia article, and I therefore agree with User:Dsc, who deleted it. And, in addition, to quote User:Dsc, June 2005, why is it relevant for our CD article? Poculum 09:38, 29 September 2005 (UTC)

Agreed. Mirror Vax 12:49, 29 September 2005 (UTC)
Relevant or not, the story is told numerous times so it is about time the myth is busted or confirmed. For that alone it is worth to include it in the article. Next month there is a Philips Natlab reunion with many of the engineers from the CD development team present (most are retired now). I will ask them if the story is true or not. I will also have access to the NatLab library in january, I will check if the coin story is present in the design documents or design meeting notes. One of the engineers told me that the very first proof-of-concept prototype didn't use the same dimensions but ran on parts made for laser disc (with a bigger center hole). Felsir 07:36, 12 December 2005 (UTC)

Compact Disc Unique Number

does anyone know if there is a unique number that differs manufactured compact disks.. like a MAC adress in network devices.. and if this unique number or ID exists.. why it is not used for copy protection.. and if this number does'nt exists why manufacturers dont adding it to there product for them it will be a simple to create a CD with uniq ID that can't be flashed or overwritened... and for software,game or audio developers it will be more easy to protect there product..

To my knowledge there isn't. All there is that could be used is that the TOC of a pre-recorded disk looks different to that of a CD-R.

CD-ROMs are mass-produced, "stamped" out from aluminum "masters". That makes all of them identical. I suspect that CD-ROM manufacturers don't add unique serial numbers because
  • (a) Adding a unique serial number would definitely add cost.
  • (b) Adding a unique serial number might bring in slightly more income from people who otherwise wouldn't have paid for the CD. Or it might not make any difference.
In other words, I suspect that the CD-ROM manufacturers don't add unique serial number because they think the (hypothetical) benefits are worth the (all-too-real) cost.
On the other hand, I've been told that CD-R and CD-RW disks are tested by writing some data and making sure that data can be read without error. It wouldn't cost anything (just a one-time change to the test software) to add a unique number to each of those disks.

No Unique Number

CD's don't contain an individal serial number. The stamper would have to be changed (ever-so-slightly) for each disc produced. While that may be true about the CD-R data test, the average single cavity replicator is capable of turning out 20,000 or so identical discs in a 24 hour period. The production time increase to burn that many discs in CD-R drives would be impractical.

There is a number that identifies the manufacturer of a replicated CD that should be printed in the "mirror band" of every disc. It is usually prefaced with the letters "IFPI". Some IFPI numbers are also injection molded into the bottom of the disc near the center hole.

Overburn

The external links to overburning information, while useful, aren't really relevant here. I'm going to move them to overburning and place a reference to that article in the Recordability section. - mako 07:06, 2 Dec 2004 (UTC)

regarding 'other burning technology' for CD

I remember something regarding cd-writers able to burn ~1 GB of data in 700-MB CDs.
I've searched, but I've only found news regarding Plextor GigaRec writers (which do what I remember, but aren't the ones I read about years ago).
Could someone, knowing|finding, write a paragraph about this?

I don't think such a thing exists. There are ways to burn a little more information, but a 45% increase...no. Unless you play the games marketeers played in the mid 90s where a given data tape would hold "750 megabytes" of data but only really stored 250 megabytes of uncompressed data. Samboy 03:16, 30 Mar 2005 (UTC)


      • Such a technology *does* indeed exist although it never caught on. It's called HD-Burn and was developed by Sanyo. There was a brief period when MOST generic CD-Burners on the market licensed and included this technology from Sanyo.***

Sources: http://www.buildorbuy.org/burn-proof.html http://www.met.com.tw/download_file/cdrw/cyqve/3080/HD_BURN_CDR.pdf http://www.met.com.tw/eng/product/prointro/desktop/cyqve/dr3080.htm http://www.cdrfaq.org/faq02.html#S2-46 http://www.digital-sanyo.com/BURN-Proof/HD-BURN/

ScottyWH 18:15, 20 Jun 2006

History

I have a problem with the intro to this section:

"The Compact Disc is not an invention: it is the convergence of a series of enabling technologies, such as laser technology, mechanics, electronics, and coding technology. Therefore, nobody can claim that he or she is the inventor of the Compact Disc."

The same sort of argument could be made for just about any invention. Take the automobile - we couldn't have cars if someone hadn't invented the wheel, wagons, metalurgy, internal combustion engines, etc. And of course we never would have CDs if nobody had invented lasers, transistors, computers, digital audio formats, etc. But just because an invention builds on previous inventions doesn't mean that it's any less an invention in its own right.

Credit for the invention should be given to Philips and Sony and their "joint taskforce of engineers."

--4.245.5.118 23:05, 25 Apr 2005 (UTC)

Thank you for starting this discussion. I find it very interesting, but also extremely difficult, as one has to answer existential questions such as what is the Compact Disc? Is it just a digital version of the Videodisc developed in the 60s and 70s? What are the additional inventive steps? Taking 44.1 kHz as sampling frequency used in the prior art PCM adaptor? Is that a creative step? (':

In the (patent) literature one can find optical audio recorders/players developed in the 1930s. Of course the technology was analog as PCM was invented in 1937. Those machines could not be mass produced as the key components were not available. In the 1960s, pioneering experiments with optical recording have been made when the gas laser became available.

Digital audio and video optical recording became feasible for the consumer market after the invention and mass production of the solid-state laser and notably low-cost electronics. The ideas of optical recording have been around for a very long time, but could not be implemented in mass quantities without those key components. This is in sharp contrast with, for example, Edison's audio cylinder and Berliner's gramophone. The low-tech key components, wax, needle, and mechanics, were already available in the 16th century or earlier, but nobody came with the idea for the gramophone, or may be nobody had interest in it.

There is, I think, no doubt that there was a Sony/Philips task force of about eight top engineers who made the required choices and trade-offs based on joint experiments and discussions. I agree that those, mostly anonimous, engineers should receive more credit for doing an excellent job around 25 years ago.

I suggest that we delete the first sentence of the CD history section regarding the inventorship, and add the names of prominent members of the task force, such as Dr Toshi Doi (Sony) and Kees Immink (Philips).

I agree: The first two sentences of the History section come off sounding prematurely argumentative and not neutral. As 4.245.5.118 points out, applying the supplied logic everywhere would negate the vast majority of "inventions". I'm certain that plenty of people (but not all) would permit something that combines existing technologies in new, novel, and previously unforseen ways to be rightly called an "invention". Thus, the existing two sentences are simply one POV in an argument, so they should be either balanced or removed. --Ds13 16:42, 2005 Apr 30 (UTC)

The following paragraph is taken from the official Philips' history web site www.research.philips.com/newscenter/dossier/optrec/index.html

\begin{quote} Almost every week Philips receives a request for an interview with the inventor of the CD. That would undoubtedly make an interesting story. How do you put the gramophone record out of date in such a short space of time? And had the inventor already envisaged subsequent developments like the CD-ROM and the DVD? Unfortunately, the inventor of the CD does not exist. Nobody even invented one part of the technology alone. The CD was invented collectively by a large group of people working as a team. Emil Berliner, the founder of Deutsche Grammophon, might have been able to invent the gramophone record on his own in 1887, but the technology on which the CD is based is too complex for just one genius. \end{quote}

So the 'official' Philips' POV is that the CD is not invented. Or even 'Nobody even invented one part of the technology alone'. Why do they want the world to believe that?

Aren't you misinterpreting the quote. They never say that the CD wasn't invented, just that every part of it was invented by a team, not a single person.

Durability or longevity of the CD medium

I think it would be appropriate to add a longevity/lifespan/durability section in the article. With so much expensive audio and other data stored on CDs, it has become more common to discuss how long the data is expected to last and what can be done, if anything, to preserve or minimize degradation and/or to recover data from an aging CD. I'm no expert (thus, I'm on the talk page!), but related topics might be:

  • lifespan under ideal circumstances
  • normal wear and tear
  • damage

There was something else i herd on the radio. Aperently if you expose an audio cd to mold for long periods of time, different effects can occour, almost like a Natural Remix (Echo, panning and interesting skips can occour). Maybe someone should check that out when listing durability. I dont remember the professor's name, but he was at an australian university

  • Seconded - CD was presented to the world as an inert, effectively immortal storage medium which proves not to be the case. I am no expert either, but I do know that I own commercially manufactured music and data CDs from the early 1990s which have taken on a bronze tinge, and which are either unusable or unreliable now. Of course different manufacturers will have had varying manufacturing standards, but even the materials used are subject to deterioration. --Ndaisley 08:23, 11 April 2006 (UTC)
  • CD: PLEASE FIND REFERENCES. As for CD-R: I added the PC-Activ magazine citation about CD-R "rot". They tested 30 brands for 2 years, and saw wide unreadable areas appear in as little as 18 months. I hope the info is not reverted out again. --Lexein 13:06, 11 February 2007 (UTC)

Adding a link?

I found a CD-R FAQ, but before adding the link, should we advise the author?

http://www.cdrfaq.org/

Eptalon

You don't need to notify the author. Also, that link should go on the CD-R page. - mako 07:20, 27 May 2005 (UTC)

Hidden Tracks

I've deleted the mention of the Abbey Road 'bonus track'. This is neither a hidden track, nor a bonus track, nor any other such thing that the article describes. It is a full-fledged track, fully intended that way and proceeds exactly the way the original LP does. --patton1138 1 July 2005 13:33 (UTC)

A good example of a hidden track would be on Rammstein's album "Reise Reise". It's a clip from the CVR from a commercial airline crash in 1985.--NRen2k5 17:10, 30 August 2006 (UTC)

"To hear the hidden track, the listener must usually "rewind" the player past the beginning of the first listed track. Not all players allow this."

Not all players have a seek-function, right? But do all players with seek buttons, including high-end models, allow for this

Compaan's idea

After adding the mention of Klass Compaan as the originator of the idea of the CD, user DSC posted the following to my talk:

"I have noticed your contribution to the Compact Disc article regarding Klaas (not Klass; it is the Dutch version of the German Claus, like in SantaClaus) Compaan. Your statement is false, see the laservision article, where you may read that Laserdisc technology was invented by David Paul Gregg in 1958, patented in 1961 and 1969, and first publicly demonstrated by Philips and MCA in 1972. It was first available on the market on December 15, 1978, two years after the VHS VCR and five years before the CD. So please delete your addition to the CD article. Dsc 10:54, 28 July 2005 (UTC)"

However CDs and laserdiscs are different and there are many [3] sites which attribute the idea of the CD to Klass so.....??--Deglr6328 02:49, 29 July 2005 (UTC)

Does all sites write his name as Klass or Klaas? As the sites that you refer to do not even correctly write this simple name, why do you think they are right regarding his invention. Yes, sure, CDs and Laserdiscs are different: they have have different disc diameters etc. BUT the essential physics, protective layer, objective lense, including tracking servos etc of a LaserDisc and CD are all exactly the same. The only difference is the addition of different (analog FM vs digital EFM) electronics for switching on/off the writing beam. The physics of the Laserdisc was invented by Gregg in 1958. Please take the time to read Gregg's and Compaan's (much later) patents, before you start copying data from web sites that copy it from other websites. So please delete 'your' addition to the CD article (that you copied from other websites). Dsc 14:25, 31 July 2005 (UTC)

I have deleted the remark regarding 'Klass' in the CD article. The reasons are as follows: it is utterly wrong despite the fact that one may find similar data on the web (all with 'Klass' instead of his correct first name Klaas). In the CD article it is mentioned that it is built on the technology of the optical Laserdisc, which is due to companies like MCA, Philips the French Thomson (see that Laserdisc article), and others. There is no need to copy all that stuff in the CD article. Just a reference to it seems to appropriate. The CD article continues around 1975 when laserdisc technology was mature, and digital audio became possible for mass fabrication. Dsc 07:43, 2 August 2005 (UTC)

The reason you only saw the Klass spelling is because that is what the search was done with! The fact remains that there are over 500 sites which mention his name as being integrally associated with the creation of the compact disc and his name obviously belongs in the article somewhere.--Deglr6328 06:25, 3 August 2005 (UTC)

In fact the only reasonable conclusion I can draw from the above is that apparently 500 web sites can be utterly wrong, as they all, note the wrong spelling of his name, Klass, copy. Optical recording, please believe me as I do not copy this from other web sites, was invented by a number of companies such as MCA, Philips, and Thomson in the late 70s. The intention was to develop a videodisc, and not an audio disc, so that the huge warehouses full of movies could be distributed. This was before the introduction of the (VHS and Betamax) video tape. Please read the videodisc article. Actually, Klaas (not Klass), Compaan started with a disc with microfiche-like pictures on a disc (read the Philips History web site). Much later, we may recognize his efforts as modern optical video recording. Nothing to do with audio. Dsc 18:35, 9 August 2005 (UTC)

Reflections: 1 - central (mirror reflection?). 2 & 3 (due to diffraction?).
Reflections: 1 - central (mirror reflection?). 2 & 3 (due to diffraction?).

blank data spiral

"Recordable compact discs are injection molded with a "blank" data spiral." Could someone please describe the physcial details of the blank data spiral? --JWSchmidt 18:11, 2 October 2005 (UTC)

See the cd-R article. I agree it is a little bit thin on the 'pre-format' wobble, and additions are welcome. Dsc 19:01, 2 October 2005 (UTC)

The only reason I asked is because this is used on several wikipedia pages as an example of a diffraction grating. --JWSchmidt 23:42, 2 October 2005 (UTC)

AAD ADD DDD

"Many CDs, especially classical music, but also many popular recordings (especially on early CDs), come with a three letter code printed on the back, where "A" stands for analog and "D" stands for digital. The first letter represents how the album was recorded, the second how it was mixed, and the third how it was transferred (inevitably a D, as the CD is a digital medium). As a result, almost all early CDs are "AAD" (analog recording and mixing, digital transfer to CD). Often this code was accompanied by a short description such as "Full Digital Recording" for DDD and "Digitally Mixed Analog Recording" for ADD. The logo of record label 4AD is a spoof of this process designation."

Some clarification is needed here, ADD does not mean it digitaly mixed, but that the mixed down recording is/was digital - it could have been digitsed before or after mixdown. Is the former or the latter more common and which did George Martin use? The former is obviously obligitory if "tube production" is preferred.

The original sentence seems pretty clear to me. If analog signal sources are digitized before being mixed into a single stereo signal, it's ADD. If analog signal sources are mixed into a single stereo signal and *afterwards* digitized, it's AAD. What else could it possibly mean? --70.130.37.179 02:26, 28 August 2007 (UTC)

Name Confusion

In the subcategory name in the CD article, it says that CDs are commonly spelled "disc" rather than "disk," because Philips has a copyright under that spelling. What spelling does Philips have a copyright under? I couldn't tell from the article. I am making a request that that section should be cleared up. Thanx. Bob the ducq 02:50, 26 November 2005 (UTC)


Physical description

Someone made changes saying that the 125 nm depth was one-sixth of the wavelength of the light, not one-quarter. They are neglecting the fact that the laser wavelength is reduced by ~1.58 in the polycarbonate (its refractive index), and thus 125 nm is almost exactly λ/4. I removed this line:

The sixth, 125 nm, (and not a quarter) of the wavelength was chosen to have a good trade-off between the push-pull radial tracking signal and the full-aperture read-out signal

Since it makes no sense given that fact. --Bob Mellish 14:43, 5 December 2005 (UTC)

Dear Dr. Bobby, Please read the article on 'Physical Format of Read-Only Discs', which is taken from the official Pioneer website http://www.pioneer.co.jp/crdl/tech/dvd/2-e.html

The pits on CDs are typically about lambda/6 deep. This enables the use of both a push-pull tracking error scheme, which works best at a pit depth of lambda/8, and three-beam and differential phase tracking methods, which work best at a pit depth of lambda/4. Please revert your changes taking into account the above findings. Poculum 20:25, 5 December 2005 (UTC)

  • Then someone has got something wrong somewhere. The wavelength used on CDs is 780 nm, and in a polycarbonate medium, that wavelength will be reduced to 780/1.58 ~= 493 nm, which divided by 4 is ~123 nm. Unless the pit depth is not 125 nm, then there's no way it's λ/6. I'll check for references to this. --Bob Mellish 20:45, 5 December 2005 (UTC)
  • Unfortunately I can't get access to the Red Book specs, but Ken Pohlmann's The Compact Disc: a handbook of theory and use lists some of them. The material can be anything with a RI of 1.55, and the pit depth spec is 0.11 to 0.13 μm. So that's right on λ/4 and not anything like λ/6. Note: this is for standard read-only CDs. It's possible that there's differences in the structure for writable CDs, which that Pioneer page may be talking about. However, the section of the WP article is talking about standard CDs. --Bob Mellish 22:13, 5 December 2005 (UTC)

Dear Dr Bobby, I understand that you courageously think that the Pioneer web page is wrong regarding the pit depth equaling lambda/6. It is of interest that you mention the Red Book. I guess that you have never read it since the Red Book does not explicitly specify the pit depth (‘: .

Figure 1, page 8a, of the Red Book specifies many mechanical parameters including the pit depth. It specifies that the pit depth should be less than (and, thus, not equal) 130 nm. However, the Red Book implicitly specifies the pit depth by specifying the strength of both the push-pull radial tracking signal and full aperture detection signal. For a maximum full aperture signal, the optimum pit depth is lambda/4n = 130 nm (refractive index n=1.5, lambda=780 nm). For a maximum push-push radial tracking signal the best choice is lambda/8n = 65 nm. Most CD manufacturers, dependent on the exact pit geometry such as the slope of the pit edges etc, choose a pit depth of around 90 nm, (which is around lambda/6n) yielding a good trade-off between push-push radial tracking and full aperture detection signal. By the way, I do not understand your confusion with the Pioneer web site, since a (written) writable CD-R does not have ‘pits’. Poculum 11:50, 6 December 2005 (UTC)

  • Well then, the original part of the article I changed was wrong, since it specified a pit depth of 125 nm (exactly), but a λ/6 phase difference, which is impossible given the 780 nm wavelength. Since you have access to the Red Book, feel free to update with the actual spec. (edit : as I see you have done.) --Bob Mellish 14:31, 6 December 2005 (UTC)

made in canada?

it has recently come to my attention that most every cd's in north america are manufactured in canada. is this true? i don't notice cause i live in the great white north.

music industry

there's nothing here about the music industry's push to make cd's [sic] more accepted and widen adoption by limiting the returnability of vinyl records in record stores. this page is mostly technical info. And what about how they have steadily increased the retail price of cd's while the manufacturing costs have steadily gone down?

Well, at this point, that would be a matter of historical trivia. A more current issue would be the deliberate bad mastering of audio-CDs so as to make the DVDA and SACD releases of the same recordings sound better. Er, could you please sign your messages? There's a button on the toolbar to do so. --NRen2k5 17:17, 30 August 2006 (UTC)

Increasing levels of clipping/distortion in pop cds

I would like to add some material about the current trend towards ever "hotter" recording levels, which, along with limiting and compression, is creating cd's which have clipping nearly throughout the entire disk. There has been some discussion about this among some old hands in the recording industry, I understand, so I would like to add it somewhere so people could be more aware of the issue.

But where does it go?

Here is the issue: CD's have a 16-bit or 96 db dynamic range, which is more than enough for any music (it is plenty for classical music, which generally has a much greater range of quiet to loud than anything else.) But recording engineers want to create "hotter" and louder cd's, so they set their recording levels so that the average recording level is close to the maximum permissible. When that input level exceeds the maximum permissible, you get clipping, a nasty kind of distortion. With current limiters and compressors, it is easy to make a cd in which clipping is occurring nearly throughout the entire cd. That makes the cd harsh and fatiguing to listen to, particularly with high quality equipment. Apparently this problem is getting more and more common.

Any suggestions on where to put this stuff?

Here are some links:

http://www.audioholics.com/techtips/specsformats/currentrecordingtrendsP1.php

http://www.mindspring.com/~mrichter/dynamics/dynamics.htm

Some guys are even trying to put together a petition to get the Red Hot Chili Peppers to rerelease some recent albums so they don't have digital clipping. http://forum.doom9.org/showthread.php?t=103702

I suggest starting a new article - maybe Loudness war? Mirror Vax 05:50, 31 December 2005 (UTC)
Cool. Bear with me, I am new to this wiki stuff. Karl
Since you created a new article as I suggested, there's no need to have a lengthly section about it here. You can place a link in the "see also" section. Mirror Vax 07:09, 31 December 2005 (UTC)
I will do as you suggest. Karl

8mm CD picture.

As it is now, the pictures of a smaller-size 8mm CD and of normal 12cm CDs are nearly identical at a glance. I think it would be useful to have a picture of one of each side-by-side.

I agree. There is a ruler showing that the 8cm (not 8mm :) ) CD is 8cm long.... well, we don't need a ruler to explain that. The two together, along with a ballpoint pen (or possibly audio cassette) for scale would be more useful. (Note: U.S. coins are not a particularly great indication of scale for those of us who don't live there). Fourohfour 10:52, 9 January 2006 (UTC)

DTS-CD

The article completely lacks information about DTS-CDs. While they are not very common, they still exist and should be mentioned. For those who haven't heard of them, instead of 16-bit PCM at 44.1 kHz these CDs contain DTS encoded audio at 1411.2 kbit/s (ie the same bitrate as 'normal' CD audio). Those can be played by most normal CD players if they are linked digitally to a DTS capable surround decoder. This may sound hackish, but is a standard. Maybe in this context Dolby Digital CDs sholud be mentioned also which is the same principle used with AC3 encoded audio, but as far as I know this is really a hack and not a standard. Belgabor 80.129.94.211 19:01, 2 May 2006 (UTC)

Good point. I see that DTS-CD doesn't seem to have its own article, nor is it included in the general DTS article. --NRen2k5 17:24, 30 August 2006 (UTC)
I created a stub for DTS-CD and added a link under 'See Also' Edokter 22:35, 15 October 2006 (UTC)

compact disc logo

1: there are many other variants of the compact disc logo other than the traditional digital audio one (digital video, digital data,recordable,no subtext at all). Does anyone know what the status of theese is.

2: are the rules different for embossing the logo into the boxes different from those for putting it on the CD, I often see CD-ROMs sold by large companies in boxes with the digital audio logo (less so than they used to as lots of software vendors have moved to using bare DVD cases as the entire package rather than CD boxes as one item in a large cardboard box). Plugwash 11:34, 22 May 2006 (UTC)

Apostrophe hell

I know this is a really minor point, but I just can't get used to seeing "Philips's" with that "s" plonked on the end. I've tried to find some rationale for why it should go, but haven't succeeded yet; quite the opposite, in fact. Can anybody out there think of a good reason to get rid of it?
—Chris (blather • contribs • e) 15:45, 11 September 2006 (UTC)

I looked into this recently. Some style guides allow you to drop the second 's' but all I checked prefer leaving it in. I couldn't find anything in the Wikipedia style guide about it. Rees11 15:19, 11 June 2007 (UTC)
Wouldn't the correct grammar be " Philips' " when using the word as a plural?Arendedwinter 06:04, 30 June 2007 (UTC)

History Section needs work

The History section appears to by copied directly from [4]. It should be rewritten to avoid copyright trouble. Furthermore, the section is just a profile of J T Russell, not a history of the Compact Disc. In particular, it should probably mention early work on digital audio recording done at Bell Labs in the 1950s, Tom Stockham's work on high-quality optical/digital sound recording in the 1970s and work by many people on coding theory, in addition to the massive quantities of important engineering work that went on at Philips, Sony and elsewhere. Tom Duff 21:52, 12 October 2006 (UTC)

Looking over the history, I see that starting about Oct 7 anonymous editors have deleted what was an adequate historical section (and some other stuff) and replaced it with the J T Russell bio. Someone with better editing chops than mine should back those changes out Tom Duff 03:39, 13 October 2006 (UTC)
I've restored the previous History section. The article on James Russell is clear in that it states that Russell's work was independent of the work at Philips and Sony. Ergo, Russell is not the inventor of the standard digital audio medium we know as the CD. -Scipius

J T Russell invented the overall concept of optical digital recording and playback in 1965, under the auspices of Battelle Memorial Institute. The concept encompassed stereo, software distribution, recordable records and multi-layer video. The first patent (of 26) issued in 1970. He built prototypes, the first was operating in 1973. In 1973, 1974, 1975 his prototype was viewed by about 100 companies, and more than 1500 descriptive brochures were sent out to various interested parties. The concept was picked up by many technical and media magazines beginning in 1972.

Corporate visitors to Russell's Battelle lab in that time period included Philips and Sony engineers. And a representative visited Philips in Eindhoven in 1974 and explained Russell's system to the Audio/Video/LP/VLP groups there. This was about 6 months to a year before Philips began to work on digital optical.

Russell's optical digital inventions and development work preceded that at Philips by about 12 years, and were available publicly from 1970. It is fair to say that Russell's concepts, patents, prototypes, and literature instigated and in some measure guided the optical digital revolution. -[User:RealStory]

Capital or lower case??

Many times in this article we see "compact disc" with lower-case initials, and many times (including in the title) we see two capital initials. Which should it be? If the former, the article title needs to get changed accordingly. Michael Hardy 03:42, 14 November 2006 (UTC)

The name of the format should always be uppercase (and thus the name of the article should be in uppercase). When talking about the actual physical disc, there doesn't seem to be consensus one way or the other. --- RockMFR 22:57, 19 November 2006 (UTC)

I, hereby, assert that it should be "compact disk". It is my impression that the word is "disk". Please do note: "doughnut", not "donut"; if doo is formed as a nut, then there could be "doonut".

Thank You.

[[ hopiakuta | [[ [[%c2%a1]] [[%c2%bf]] [[ %7e%7e%7e%7e ]] -]] 00:09, 2 December 2006 (UTC)

Spin

Which way do the disks spin? Clockwise or countercloskwise? Am I missing something? 71.102.186.234 11:43, 9 December 2006 (UTC)

Manufacture

[(Temporary note, from a volunteer editor:) The paragraph above seems to have been written to describe laserdisc manufacture, and edited somewhat to describe CD manufacture. A 12-inch/30cm glass master is not for CDs, and the mention of foil doesn't look correct. Noted in the Edit summary. Apologies for the informal format!] —The preceding unsigned comment was added by 66.92.74.189 (talk • contribs) 17:40, February 5, 2007.

Image in Infobox

Is there a reason why we're using a vector image representation of a CD in the infobox? Isn't there a clean, hi-res photograph of an actual CD we could use instead? Pele Merengue 22:52, 22 March 2007 (UTC)

No good reason for it. I've replaced it with a real Commons image. ProhibitOnions (T) 20:49, 30 March 2007 (UTC)

"Shape CDs?"

The source for the information appears to be a video here: http://dabble.com/node/11373553 (I believe it's in German). I really do not think that one Mario Koss with a little side business hacking CDs into works of art (which I assume that they are, since it's doubtful they are playable in that condition) is significant enough to have a mention on an article about general technology standards. Therefore, I have moved the content here for now. If anyone disagrees, just tell me why I'm wrong, and put it back. vLaDsINgEr 02:31, 17 May 2007 (UTC) Also, the contributor who added this might have some non academic motives, seeing as how he (User:Chernavsky George Yury) is the songwriter (Yury Chernavsky) on the CD pictured, and has collaborated on records for the company Pikosso Records (makers of the "Shape CD"). I suggest that the information be rewritten from a nonpartisan standpoint.


Shape CD (example)
Shape CD (example)

Shape CD – is a type of CD-Rom or audio-format, but comparing with the usual round compact disk it has outlined as a contour of the objects like a cars, artist’s portraits, stars, heart-sign, Disney characters, credit cards and etc. (Shape CD was patented by German producer Mario Koss in 1995). Shape CDs are very popular mostly in the entertainment industry,

CD + Microwave

Preston + Steve did a Science Day, and they put a CD in a Microwave, and it glowed purple. --66.218.11.201 00:07, 25 June 2007 (UTC)

Data structure - sector and sector/frame ambiguities

This topic is in need of attention from an expert on the subject.
The section or sections that need attention may be noted in a message below.

In section 3.1 Data Structure the term 'frame' is described, and it amounts to 588 bits. This threw me at first, because I'm familiar with CUE sheets from CD extraction applications such as Exact Audio Copy (EAC), which, just like a CD track index can denote track marks (INDEX points) to 1/75 second accuracy, because CD audio data is divided into 588-sample chunks (=44100/75). With stereo, 16-bit, that's 2352 bytes of payload (=18816 bits of payload) and certainly not as little as 588 bits of anything! Confusingly, in most references such as the EAC FAQ and hydrogenaudio.org Wiki, especially when referring to CUE sheets in EAC, these 588-sample, 1/75 s chunks are called 'frames', and obviously these differ from the tiny 588-bit (not 588-sample) data frames referred to in this Wikipedia article, about which I know nothing and can only accept what I read here or follow up the references. Might the 1/75s chunks be called 'sectors' in this article and 'frames' elsewhere? Well no, I don't think so.

The CUE sheet frames are in my experience definitely 588 samples wide, and therefore must contain 2352 bytes of PCM audio payload at 16-bit depth, 2 channels. Yet section 3.1 of this article states:

Data on a CD-ROM are organized in both frames and sectors, where a CD-ROM sector contains 98 frames, and holds 98×24 = 2352 (user) bytes, of which 304 bytes are normally used for sector IDs and an additional layer of error correction, leaving 2048 bytes for payload data.

I take issue on a couple of points. Firstly, the paragraph to which this belongs is clearly supposed to still be about CD audio (red book) with EFM and CIRC codes, while CD-ROM (mentioned twice in the quote above) is talked about in section 4, which happens to be the next paragraph. Secondly, it's CD-ROM data not CD audio that has the additional third layer of error correction and proper sector identification that both reduce its data payload capacity compared to red book audio CD's payload.

I'm tempted to think some info about CD-ROMs has been incorrectly presented as CD audio data structure, and that frames in red book are actually much larger, containing 2352 bytes (588 samples, 1/75 sec) of user PCM payload, with additional overhead for error correction bits and the like, and possibly some type of synchronisation sequence that uniquely identifies frame boundaries to aid random access based on the table of contents (analogous to the CUE sheet) that may define up to 99 tracks.

If anyone has verifiable sources or personal knowledge enough to remove the fallacies and correctly name and describe the data structure on an audio CD, please edit the Wiki, crediting any sources quoted and possibly indicating very clearly that this section covers the data structure of audio CDs (red book) only and not that of data CD-ROMs, which ought to be covered in the CD-ROM article. With apologies for verbosity, but I feel I need to specifically point out the flaws--Dynamicimanyd 22:18, 2 August 2007 (UTC)

Well, if your are confident that your knowledge is correct, you are welcome to edit the article yourself. In any case, I tagged the section asking for expert input. --Edokter (Talk) 23:23, 2 August 2007 (UTC)
Thank you for tagging it, Edokter. I'm only confident that it's wrongly talking about CD-ROM data structure in a section about audio CDs. I don't have confidence in technical details of the whole data red-book structure, only fairly firm knowledge of the 1/75sec = 588 sample-pair indexing resolution, so I'm unable to add much of use. I'll check the Red Book (audio CD standard) article for further info, though I don't remember seeing this sort of detail.--Dynamicimanyd 20:05, 3 August 2007 (UTC)

Further to checking the Red Book article, it is disputed. It does mention 588-sample sectors read at 75 sectors per second, but not any frames of 588 bits each.--Dynamicimanyd 20:19, 3 August 2007 (UTC)

Biggest problem seems to be the meaning of a frame and a sector. The red book article states that sectors hold 2352 bytes of music (x 75 = 176,400 bytes / 2 tracks / 16 bits = 44100 samples). Also, look what I found on an old wikpedia mirror (meaning it was here once):

A CD-ROM sector contains 98 frames, and holds 98×24 = 2352 bytes. The CD-ROM is in essence a data disc, which cannot rely on error concealment, and it requires therefore a higher reliability of the retrieved data. In order to achieve improved error correction and detection, a CD-ROM has a third layer of Reed-Solomon error correction. Note that the CIRC error correction system used in the CD audio format has two interleaved layers. A Mode-1 CD-ROM, which has the full third layer error correction capability, contains a net 2048 bytes of the available 2352 per sector. In a Mode-2 CD-ROM, which is mostly used for video files, there are 2336 user-available bytes per sector. The net byte rate of a Mode-1 CD-ROM is 44.1k×2048/(6×98) = 153.6 kB/s. The playing time is 74 minutes, or 4440 seconds, so that the net capacity of a Mode-1 CD-ROM is 682 MB.

I wouldn't actually mind getting rid or simplyfying the Data structure section alltogether, as it is overly technical anyway. — Edokter • Talk • 10:47, 8 August 2007 (UTC)

Thanks for this detective work, Edokter. A Google search for 2352 bytes 75 CD revealed links to Wikipedia, of course, numerous forum posts and a few patent texts. A couple of them mentioned the concept of A-Time (absolute time since the start of the CD album) versus TR-Time (relative time since the start of the current track). And US patent 6119116 from an IBM inventor in Sept 2000 in particular verifies this and explains that both of these time formats are...

...expressed in minutes, seconds and frames, mm:ss.fff. Each frame corresponds to one sector which is 1/75 second. One sector or frame, it will be recalled, is equivalent to 2352 bytes of user data in Red Book format.

(emphasis mine)

The same information is present in an earlier patent from 1995 too, and tends to back up the accuracy, which in any case, a patent applicant is likely to be careful about, especially one from any of the major technology companies, including IBM.
Additionally, the further info regarding CD-ROM structure is exactly of the sort of magnitude that made sense when I read all this in the past, and the reduced payload in the same frame size makes sense, and I remember it was a power of 2 (2048 bytes for Mode-1 CD-ROM).
I'm confident enough that I'm going to simplify things and make an edit to the main article which was clearly wrong or misleading before. I'll leave the expert help tag on. --Dynamicimanyd 21:10, 15 August 2007 (UTC)

I have tried to rewrite the CD data structure, but I am afraid that Edoktor does not allow me to do so. Edoktor does not understand the difference between a sector and a frame (he apparently does not have a copy of the red book). He discusses C2 errors, while this is not the place to do so. I leave it in this messy state as I have no interest to see my work being ruined by a non-specialist. Izab1 16:04, 16 August 2007 (UTC)

I welcome any action that clarifies the technical aspects of the CD, but you removed an entire chunk of information (added by Dynamicimanyd btw.) that was at least a considerable improvement of what was there before. As explained above, in the music domain, one second of music constitutes 75 frames, not sectors. And as far as I know, one frame occupies one sector. Please tell us what the Reb Book says, and I'm sure we can come to the right defenition for all the terms. — Edokter • Talk • 17:11, 16 August 2007 (UTC)

What do you mean by "in the music domain"? You said: "And as far as I know, one frame occupies one sector." Do you know anything about this topic? Do you have a copy of the Red Book? Pls reverse this article to the state before you and Dynamicimanyd ruined it. Izab1 19:04, 16 August 2007 (UTC)

We "ruined" it? Did you actually read the entire discussion above? The problem is we have to go with whatever sources we can find, and the sources mentioned above say 1 sector = 1 frame. If we are wrong, the please prove us wrong and tell us what the Red Book says about sectors and frames. — Edokter • Talk • 19:15, 16 August 2007 (UTC)

Yes, I read it. It reads for example and obviously these differ from the tiny 588-bit (not 588-sample) data frames referred to in this Wikipedia article, about which I know nothing So he honestly states that he does not know, and also you, I infer, have not the slightest idea what you are doing. So pls reverse it to the state before you both started to ruin it. It was just fine, and in line with the red book, which, btw, is the only reliable source. The rest is "music domain", what ever that means.Izab1 19:41, 16 August 2007 (UTC)

You're not much help. I'll have to research it myself then. But I think I laready see the confusion: you are refering to s physical (288 bits) frame, while we have the logical (288 samples) frame/sector in mind. When I'm done, I'll try incorporating it into the article. — Edokter • Talk • 20:02, 16 August 2007 (UTC)

Izab1, I'm sorry that you feel I have ruined it. However, the previous state did include information about data CD-ROM structure in the same paragraph as discussion of audio CD structure, which was a best confusing. It also contained no citations or references. I was careful enough to look for confirming information, and I believe that Patents tend to have to be worded carefully enough with accurate information about the background art to be trustworthy sources, and if they're old enough they won't be quoting sources like Wikipedia and private web pages that may contain suspect information. I also found the same information in 2 patents (though I only cited the clearest) and it backed up by previous knowledge of the subject (which was second-hand, not direct from the Red Book). If you can find good references to cite for the previous assertion that Red Book frames are 588 bits, not samples, and differ from sectors, then I'd be only too happy to learn something and improve my knowledge (and printed sources, such as the expensive Red Book itself, would be fine - just cite the source and page/section number as you would in a scientific journal and anyone with the will can verify the facts). My understanding reflects terminology and numbers that are widely quoted on the web and in some printed sources like patents and accords with the structure of CD-derived lossless audio files with which I am familiar.

I'd be delighted if User:Edokter can discover whether his hunch is right, and if so, whether the word frame is used for two different entities, one in the physical structure and one in the logical structure, or some other word is used or a combination such as physical frame versus logical frame.

I'd be happy to have the C2 error passage cleaned up or removed, though I believe it adds some background to the difference between audio CD and CD-ROM storage capacity and error correction layers.

I hope we can enjoy a civil discussion and get some good sources to firm up the quality and clarity of information presented--Dynamicimanyd 20:22, 16 August 2007 (UTC)

Data structure - section break

Several online sources confirm the 588-bit frames, so I did a major rewrite. I also removed some information that is beyond the scope of the article and made it more readable for the average reader. I hope it meets everyone's approval. — Edokter • Talk • 11:00, 17 August 2007 (UTC)

I am glad that you have rewritten the section to essentially the state before it was improved a few days ago. The original text was just fine. I have edited your text, since at places it was false, as for example, mode II does not have any 3rd layer ECC. It would be nice if you could read the literature prior to imroving the text. The section on timing is false, but I have no time to rewrite it. I do hope that you will study this topic, and revert or remove the text. Izab1 14:44, 17 August 2007 (UTC)
First, I only edited what was already there (or in the history), so I can't be blamed for the mistakes regarding the mode II error corection. Second, I do think you use to many 'scholary' words. This is an encyclodepia article, not a research paper. And like I said, I can't read the literature, and have to make due with what's online. Regarding the timing section, I ask you again to quote the relevant text from the red book. I do know that 99% of all editing applications do refer to the 1/75th timing as a frame, and I have indicated it as such. — Edokter • Talk • 15:09, 17 August 2007 (UTC)

Thank you both for the great improvement in clarity that has resulted from this extra research and rewriting. I'm sorry that my discovery of sources with the wrong use of frame led me to confuse things in the meantime. The subsection "Frame" is particularly useful in disambiguating the two kinds of usage, both of which feature the magic number of 588.--Dynamicimanyd 19:44, 21 August 2007 (UTC)

Source for 30-billion-a-year number?

Anyone know where that 30 billion number in the introduction comes from?

That's a HUGE number... I'd love to see how that number was reached.

I have been hunting for similar data on floppy disks, too... if anyone knows.

--Beagley 18:42, 27 August 2007 (UTC)

Removed "anual". More likely the total sales since it's introduction. — Edokter • Talk • 21:39, 3 September 2007 (UTC)

Yesterday I wrote, quoting the BBC (and thus Philips) that 200 billion CD audio discs have been sold in 25 years. Ignoring the relatively low sales in the first 10 years, we estimate in 2007 a sales of around 20 billion audio discs. So adding sales of Cd-R and CD-ROM it is very likely that much more than 30 billion discs are sold in 2007. So it seems like a good idea to revert the edit.Sabbah67 14:31, 5 September 2007 (UTC)