Talk:Compact Disc

Size of the data-holes

I am interested in the size of the data-holes (the binary is stored in various small holes) and cannot find any info on the topic. Any of you know the radius of the holes? --Shivaya4 (talk) 09:16, 8 February 2010 (UTC)

The term I searched for was q=compact+disc+pit+radius; from which the seventh and eighth results gave values of:

Source	Pit depth	Width	Length
[1]	110–150 nm	600 nm	830–3,600 nm
[2]	100 nm	500 nm	850–3,500 nm

The first of those gives reasonable explanations for two of the values (subdivision of the wavelength of the light used) and lengths being 3–11 times bit rate (at 1.2–1.4 m/s), but perhaps you can investigate further (eg. the Patents) and come back with what you've found. The first also points out the length varies depending on the linear velocity across the CD.

I note that this is your first contribution to Wikipedia (welcome), so I really hope I didn't just do your homework for you. —Sladen (talk) 09:51, 8 February 2010 (UTC)

Compact Disc release dates

I am confused by the various dates given for the release dates of the CD onto the general market, Some dates show 1980 some 1982, however, I have handled and listened to a CD in 1977/8. Also, Philips claims to have invented the CD in order to replace their Cassette Tape invention, but a Mr Russell claims to have invented the CD around 1965. What's correct? Barry. —Preceding unsigned comment added by 203.129.146.52 (talk) 07:12, 26 February 2010 (UTC)

Barry, you are absolutely right. I brought this error in the wiki page up a number of years ago, but it was decided by...someone who wasn't alive in 1970 and held a CD in their hands...to maintain that the compact disc was invented in the 80's by Philips. James Russell did, in fact, invent the compact disc in 1965. This is a perfect case in point why Wikipedia cannot be used as a reference in legitimate historical discourse.

Phearox (talk) 17:37, 4 July 2011 (UTC)

Guys, this has been discussed multiple times. There are links to the archives closer to the top of this page. Click on them and use your browser to search for "russell".

Wikipedia would be a worse resource if it relied on "I was there" or "I am an expert" kinds of unsubstantiated claims, no matter how true or plausible they may be. If Russell invented the CD as we know it, surely there will be some historical, citable published somewhere about it. If there is a noteworthy debate on the subject, surely the debate itself has been covered in a newspaper, journal, conference paper, or thesis. Otherwise it's just folklore. Familiarize yourself with the Wikipedia policies WP:V and WP:RS and come back with things we can cite. —mjb (talk) 18:39, 4 July 2011 (UTC)

Well, There are patents in his name on the subject (yes, the original purpose was video and audio together, but the technology is unarguably covered by the patents): http://www.google.com/patents?vid=3501586, http://www.google.com/patents?vid=3795902 (Ironically, I found these right on his Wikipedia entry...) There are meeting minutes from live discussions with the man himself: http://www.aes.org/sections/pnw/pnwrecaps/2005/russell/. You could also tell the Massachusetts Institute of Technology they are wrong if you like: http://web.mit.edu/invent/iow/russell.html.

I don't mean to sound combative, but this is something that has frustrated me for years - the presence of such an overabundance of evidence (patents, live presentations and meetings, even research by respected educational institutions), and yet there is not even the slightest mention of Russell in the compact disc entry of Wikipedia. An absolutely essential piece of the compact disc's history has been omitted from a resource some children in school often take as gospel.

I wouldn't defend this point so vehemently except that I /held a CD in my hands/ prior to the supposed invention by Philips. The stance that Sony/Philips invented the CD is preposterous on its face. Phearox (talk) 19:34, 4 July 2011 (UTC)

Naturally, there is always prior art that contributes to aspects of a given technology. When writing the history of pretty much anything, one must make editorial decisions on where to start telling the story. How far back do you reach? How much of the technology that predated and/or was built upon to create what we know today as the Compact Disc needs to be mentioned in the article on the Compact Disc? There's already an optical disc article linked to from the lead, and a videodisc one as well. Those have their own histories which overlap some with the CD history. I mean, I don't doubt that you held in your hands an early optical disc that maybe contained audio and/or video data in some pre-Red Book format. Was it all-digital? Was it referred to as a Compact Disc, the name Philips came up with in 1977–1979, as reported by the BBC? I'm guessing no and no. So if you held something more aptly described as CD-like, is it not an overstatement to say Sony & Philips are wrongfully claiming to have created the CD? Compact Disc is a specific name for a specific combination of technologies and standards. It's not a generic name for all small audio optical discs ever invented or demonstrated. So lines have to be drawn.

I hope I don't sound intractable; there's always room for improvement in any article, and this one is no exception. Others may disagree, but I personally don't think it would hurt the article to make some mention of Russell's work, using whatever good sources we can find. But we do have to avoid characterizing it in the way some seem to be advocating, which is along the lines of "Sony and Philips have perpetrated a great fraud, lo and behold the CD was actually invented by someone else, as shown by these patents." You'll have more success if you try not to focus on debunking; the article has to focus on how the CD as we now know it came into existence, without reaching too far into the history of all optical discs or placing undue importance on dead-end branches of digital audio disc research. —mjb (talk) 23:12, 4 July 2011 (UTC)

I would suggest that the information you present about James Russell could help improve Optical_disc#History. Be careful about using primary sources they're useful in some technical contexts but using them to try and demonstrate who was first would probably constitute original research. --Kvng (talk) 19:53, 6 July 2011 (UTC)

Disc Manufacture Clarification Request

After reading this article, I am left unclear on the manufacturing process. In the Manufacturing section, does the initial disc formation from plastic granules introduce a spiral into the resulting surface? Later, does the data die press the data into the metalic layer alone? Is the thin, metal coating thick enough to hold the data or is the plastic substrate involved? Without clarity on these areas, I am left unable to think clearly about the physics of what happens when a disc degrades. Of course, commercially recorded discs, writable discs, re-writable discs, etc. are all different. My hope is that this article will be updated with greater detail in the Manufacturing section. Ideally, a disc diagram clearly showing the location(s) of the spiral and data will be provided. I suspect that the data reside in two places: in the metalic layer and in the plastic substrate upon which the metalic layer has been coated. However, it isn't clear to me how data could be introduced into the plactic substrate without the use of heat. Heat is not mentioned in the data impression step. --JimOfCR (talk) 15:37, 13 April 2010 (UTC)

It would be great to have this information added to the article (eg. with a diagram showing the construction at each stage of manufacture). Could you possible assist in researching it (eg. the best place to start is probably the original Philips patents). —Sladen (talk) 17:05, 13 April 2010 (UTC)

I too found the manufacture section lacking, specifically with "After a metallic reflecting layer […] is applied to the clear blank substrate…" but no mention of how this seemingly magical process is accomplished. I will continue my search as to how a metal so finicky as Aluminum can be deposited over 100-500µm "pits" and "lands" of polycarbonate plastic without destroying it. Hopefully someone more knowledgeable will be able to expound the article to include a more detailed explanation of this extremely interesting part of the process. —98.210.138.200 (talk) 05:02, 21 December 2010 (UTC)

the longest cd

The longest known single compact-disc is The Rest of New Order by New Order, which lasts exactly 80 minutes (80:02 with pregap), which is the longest a single CD album can go. Maybe this should be mentioned in the article. —Preceding unsigned comment added by 213.83.125.225 (talk) 09:00, 24 June 2010 (UTC)

The same sentence above was inserted[3] verbatium today on the Album article, also without citation. —Sladen (talk) 09:11, 24 June 2010 (UTC)

Physical parameters

This says that the speed is different from the edge to the middle. OK. But it also says the RPM is different from edge to middle! That's literally impossible! What the heck is going on here? --Jtle515 (talk) 17:22, 14 July 2010 (UTC)

Speed and rpm are the same thing—rpm is spinning speed—and the spinning speed lowers as the CD plays. It starts revolving fast at 495 rpm at where the laser is reading a short inner track near the middle, then gradually and smoothly reduces in rpm (spinning speed) until the laser is near the outside edge and the rpm is about 212, for a maximum length CD that has data all the way out to the outside edge. The laser reading speed is constant, called a constant linear velocity (CLV)—it reads about 1.2 meters (47 inches) worth of pits and lands every second for a 1x speed realtime player. To me, the article is quite clear and I don't see the need to modify it. Binksternet (talk) 18:27, 14 July 2010 (UTC)

Speed and RPM are two different things- Speed is linear, and because of the increased radius near the edge, would be higher than closer to the center on a CD. RPM is the same no matter what- the 'top' point of a disc on the outside and on the inner part will always reach the 'top' at the same time. Think of it this way, if you spin the disc 360 degrees in one minute, you are spinning every point on that disc 360 degrees in one minute. RPM is the same, in this case 1 RPM, while speed is different, as the point on the outside has to cover more distance than the inner point in the same amount of time. 66.143.200.27 (talk) 05:30, 11 December 2010 (UTC)

History Compact Disc, further reading

Hans B.Peek, "The Emergence of the Compact Disc", IEEE Communications Magazine, Jan. 2010, pp.10-17. —Preceding unsigned comment added by Peek (talk • contribs) 11:04, 25 July 2010 (UTC)

CD Playing time

A careful read on this article http://www.exp-math.uni-essen.de/~immink/pdf/beethoven.htm will reveal that the cd playing time of 74 minutes is more of a competition thing between Sony and Phillips than the usual story about Beethoven'w 9th. I would suggest reading the article and maybe correct the wikipedia article. —Preceding unsigned comment added by 88.218.48.34 (talk) 19:18, 27 November 2010 (UTC)

2-hour mono CDs announced in 1986

A Feb. 22, 1986 article in Billboard repeated a claim from Qualiton Imports that the BIS Records label was going to release CDs which, due to their mono content, had 2-hour playing time per disc, breaking the (then-) 75-minute barrier. The actual CDs that got released were nothing special: Gould Plays the Piano in Stockholm, 1958 2-CD set and Nicolai Gedda: Verdi 2-CD set, naturally both just containing mono content mastered in 2 channels. Apparently the Billboard article was a gross misinterpretation of the actual release announcement, whatever it was. Red Book doesn't allow for a 1-channel audio stream, does it? And the subcode can't theoretically address more than 99 minutes, anyway, right? Or was such a thing actually possible? —mjb (talk) 07:45, 28 January 2011 (UTC)

I recall that the disappointment of twin mono CDs was that the hardware vendors did not offer a CD player to address the format. No CD player I ever saw was able to play one channel and direct its sound to both Left and Right output jacks, then start over at the other channel and do the same thing. Binksternet (talk) 13:36, 28 January 2011 (UTC)

One of the major errors of the Red Book spec is that it assumes all recordings will be two-channel. (Hey, who wants to listen to mono?) Oddly, a quadraphonic format was spec'd, but it wasn't playable on two-channel machines. Duh. WilliamSommerwerck (talk) 14:03, 16 February 2011 (UTC)

CDR Capacity and Speed

Firstly, would there be any value in updating the stated maximum write speed of CDRs to 52x as these are now widely available? Secondly, how about mentioning CDRs with a capacity of 90mins/800MB and 100mins/900MB? They're available at various online stores in the UK and I imagine elsewhere, too. (One site picked at random: www.digitalpromo.co.uk) SP1R1TM4N (talk) 18:15, 10 February 2011 (UTC)

History

The History section is badly over-written. It can be cleaned up without removing useful content. I'll take a crack at it later today, or tomorrow, unless someone objects. WilliamSommerwerck (talk) 14:06, 16 February 2011 (UTC)

Blu-spec merge

Edokter (talk · contribs) has suggested a merge of Blu-spec CD into this article. We might want to also consider a few other similar techniques as part of this proposal.

• DSD-CD (Sony)
• K2 High Definition (JVC)
• XRCD (JVC)
• HDCD (Pacific Microsonics/Microsoft)
• SHM-CD

I oppose this proposal. I could not find a good place to work in this material. It looks like Compact Disc manufacturing might be a more workable merge destination but I am reluctant to clutter that article with these marketed refinements to the basic process. --Kvng (talk) 13:36, 8 May 2011 (UTC)

I support this proposal As the Two formats are compatible and the Blue-spec CD is playable on any CD player, I think it would make for a noteworthy section in the Compact Disk article. z'Comandif l'Statentaru l'Zeklingtonum! (talk) 22:24, 9 November 2011 (UTC)

30th birthday coming 17 August 2012

It would be good to have the article improved to meet WP:Featured article standards in the next few months so that it can be featured on the main page on the 30th birthday of the CD: 17 August 2012. Binksternet (talk) 02:51, 11 December 2011 (UTC)

James Russell the CD inventor

This must in History: "The Compact Disc, or CD, is an optical disc used to store digital data, originally developed for storing digital audio. In 1965, James Russell acted upon his idea that the music industry needed a new medium whereby a gramophone record and the needle on a phonograph would no longer come into contact with one another. With an interest in lasers, Russell soon began his research in an optical system that would replace a phonograph's needle and replace it with a laser that would read codes in order to record and playback sound.[173][174] At 12 inches (30 cm) in diameter, Russell in 1970 had successfully invented and built the world's first compact disc that contained digitized codes etched onto the disc that could be read from a laser.[175][176][177][178] After partnering with Digital Recording which was later acquired by Optical Recording Corporation, Russell and the parent company that he worked for, found it increasingly difficult to enforce and protect his patents from infringement by competitors such as Sony, Philips, and Time Warner who all profited from Russell's invention. The belief that Dutch and Japanese scientists "invented" the compact disc is a misconception in the sense that Philips and Sony used Russell's underlying technology in order to develop a disc more refined, practical, smaller and sophisticated. In 1982, Sony and Philips had commercially introduced the compact disc, twelve years after Russell had already created a working prototype in 1970. By 1986, Optical Recording decided to legally act by suing Sony, Phillips, and Time Warner. Two years later, the company came to a licensing settlement with Sony and soon thereafter, agreements with Phillips and others soon followed, including a June 1992 court ruling that required Time Warner to pay Optical Recording $30 million due to patent infringement." — Preceding unsigned comment added by 87.160.120.223 (talk) 15:49, 22 January 2012 (UTC)

http://inventors.about.com/od/qrstartinventors/a/CD.htm http://web.mit.edu/invent/iow/russell.html — Preceding unsigned comment added by 87.160.98.84 (talk) 16:22, 22 January 2012 (UTC)

http://www.google.de/imgres?imgurl=http://www.babusinesslife.com/Media/images/EntrepH0509-James-T-Russell-ea00887c-56f2-4649-8471-2063986ff745.jpg&imgrefurl=http://www.babusinesslife.com/Tools/Entrepreneurship/The-Digital-Music-Revolution.html&usg=__J9XXQwXyu19tJTkOCkMgmBw5AUw=&h=412&w=605&sz=49&hl=de&start=0&zoom=1&tbnid=1bYdt99WYhV0QM:&tbnh=127&tbnw=186&ei=TkEcT_eUBImCtQaTzLVH&prev=/search%3Fq%3DJames%2BT%2BRussell%26hl%3Dde%26biw%3D1170%26bih%3D639%26gbv%3D2%26tbm%3Disch&itbs=1&iact=hc&vpx=95&vpy=153&dur=177&hovh=185&hovw=272&tx=131&ty=202&sig=113535680373983037897&page=1&ndsp=21&ved=1t:429,r:0,s:0 — Preceding unsigned comment added by 87.160.96.158 (talk) 17:05, 22 January 2012 (UTC)