Last-modified: 2003/05/25
Version: 2.46
Send corrections and updates to Andy McFadden. If you have a question you'd like to see answered in here, either post it to one of the comp.publish.cdrom newsgroups (if you don't have the answer), or send it to fadden@fadden.com (if you do).
This FAQ is usually updated about once a month. If you are looking at a version that is more than two or three months old, it may be an out-of-date copy. The most current version is always at http://www.cdrfaq.org/.
This was originally developed (and is still maintained) as a Usenet newsgroup FAQ. If you'd like to check out the newsgroups, point your news reader at the following (or go to http://newsone.net/ and read them with your web browser):
The "canonical" FAQ is available from http://www.cdrfaq.org/ in HTML format and from the MIT FAQ archives in plain text format. You can get an all-in-one-file version of the HTML in a .ZIP file, suitable for printing. Some translations are available:
If you're maintaining a translation, or just really want to know what has changed since the last update, you can get a set of context diffs in a .ZIP file.
Please DO NOT post copies of the HTML version on your web site unless you plan to keep them up to date automatically. I have on several occasions received e-mail from people reading versions that are several months old. Just use a link to the www.cdrfaq.org site instead.
| Search www.cdrfaq.org pages with Google: | |
The last-modified date of each section is shown below the Subject line. The date format used is YYYY/MM/DD. The date stamps were added on 1998/04/06, so you won't find any older than that.
This version of the FAQ is generated automatically by faq2html, an application developed specifically for converting the plain ASCII version of the CD-Recordable FAQ to HTML. The program is available in source form.
This document is Copyright (C) 1996-2003 by Andy McFadden, All Rights Reserved. All of the content here, except for attributed quoted material, is my original work.
Free distribution of the this FAQ is encouraged, as are conversions to HTML or other formats and translation to foreign languages, so long as no content is removed, and additions are clearly marked.
The plain ASCII text and www.cdrfaq.org HTML versions aren't otherwise restricted, but other conversions might be (the content is free, the presentation or translation might not be). Check with the publisher.
The date and version number on the FAQ *are* considered part of the content that must not be removed. I occasionally get messages from people who don't realize that the copy they're reading is more than a year and a half old.
Caveat lector: the information here is derived from Usenet postings,
e-mail, and information on WWW sites. As such, it may well be DEAD WRONG,
and you are encouraged to verify it for yourself.
I take no responsibility for damaged hardware, CD-Rs turned into coasters or frisbees, time lost, or any other damages you incur as a result of reading this FAQ. Information on specific models of hardware and software is based on *opinions* of other users, not scientific studies. I am not an expert in this (or any other) field. Everything here could be a total malicious lie, and should be treated as such. You have been warned.
I don't get paid to plug anybody's software or equipment. The sections on "what XXX should I buy" are not here because I want to sway purchases one way or another, they're here because the questions are asked *a lot*, and the answers are pretty consistent. You are invited and encouraged to investigate the capabilities and reputations of all products.
The various product and company names are trademarks of their respective companies.
Visit http://www.clari.net/brad/copymyths.html for a mini-FAQ on copyright laws.
This document attempts to answer Frequently Asked Questions about Compact Disc Recordable technology and related fields. It was originally developed as a Usenet newsgroup FAQ, and is updated and posted around the middle of each month. The main foci are explaining CD-R technology, describing hardware and software solutions for creating audio CDs and CD-ROMs, and helping people find solutions to common problems.
The FAQ is heavily biased toward PCs and computer-based recorders, because that's what I'm most familiar with, but I have made an effort to include useful information for owners of other equipment. I don't anticipate the section on stand-alone audio CD recorders expanding greatly, because they're far simpler to operate than computer-based recorders, and most of the "must know" information about them is more appropriate in an FAQ on stereo systems or studio recording. I do try to address deficiencies in Macintosh coverage.
I don't usually address questions that can be phrased, "how do I make my software do this?" The answers to those should be in the manual that came with your software. In general, this is a collection of answers to specific questions, not a "how to" guide. I have tried to make the answers easy to understand by an inexperienced user, but if you know absolutely nothing about recording CDs then some sections may be confusing.
This is not a newsletter. Actively maintained web sites are a much better source of breaking news than this document, which is updated at most once a month. I also don't try to track moving targets, like CD recorder firmware versions or software versions unless a specific release is especially interesting. Ditto for which recorders work with which packet-writing solutions, or which recorders can overburn.
This FAQ does not, and will not, cover DVD, DVD-ROM, DVD-R, DVD-RAM, DVD+RW, or any of the other formats in the ever-expanding DVD morass. There are other resources on the web for DVD topics.
You will not find a lot of detail about "backing up" copy-protected software, or where to find unlock codes or "warez". There are many web sites that explain these matters at length.
All sections are tagged with a modification date, so you can see how long ago something was revised. If you want to know *everything* that has changed since last time, you can get a set of "context diffs" from http://www.cdrfaq.org/txtdiffs.zip.
Highlights:
Added sections (2-46), (6-7-16).
There are a few translations available.
Hungarian, by Nagy Szabolcs: http://delfin.klte.hu/~nagysz/cdrgyik/.
French, by Marc Kergomard: http://www.lagravuredecd.com/.
Russian, by Oleg Nechay: http://members.tripod.com/greatkorzhik/cdrfaq.htm.
Italian, by Marzona Simone: http://web.tiscali.it/marzonaontheweb/faq/faq.html.
Italian, by Simone Parca: http://digilander.iol.it/cdrfaq/ (an older version; formerly at users.iol.it/parsi/).
Spanish, by [[[CAM]]]: http://cdrfaq.webcindario.com/CDRfaq.htm.
French, German, Italian, Portuguese, and Spanish translations can be done through http://babelfish.altavista.com/translate.dyn. This is an automatic language translator that is HTML-aware. It only translates the first part of each document, so it's not entirely helpful if you just want to read a translation, but it may make doing a full translation much easier. (The translation is pretty good for an automatic translator, but is still pretty rough. I don't want to post a translation that is inaccurate or misleading, so I'm not going to run the FAQ parts through babelfish automatically.)
If you're interested in translating this FAQ, you are welcome to do so, but please respect the amount of work that I and others have put into it. Don't strip out sections, remove author attributions, or hide the revision date of the document. I don't think the terms in section (0-1) are terribly restrictive. If, for whatever reason, you can't keep up with every update of the English version, that's fine; all I ask is that you include a link to the www.cdrfaq.org version, so that the current information is easily locateable. (Some commonly updated things, like the list of recorders in section (5-1), don't need much translation.) If you don't want to translate a particular section, just leave it in English.
If you want to start with an HTML version, use the pages from http://www.cdrfaq.org/. If you prefer to do the translation on a text document, and you're converting to an iso-latin language, the "faq2html" converter that I use can be found in the "downloads" section on http://www.fadden.com/.
If you do a translation, let me know and I'll put the URL here.
This FAQ covers the three newsgroups in the comp.publish.cdrom hierarchy, one for software, one for hardware, and one for multimedia. The names of the newsgroups imply that the intended topics are related to publishing material on CD-ROMs, but the current discussions cover most everything related to CD-Recordable devices.
Here are a few guidelines. These aren't hard and fast rules -- nobody died and put me in charge of making the rules -- but if you're not sure what the appropriate subject matter is then this may be helpful.
news:comp.publish.cdrom.hardware is the most popular of the groups. Appropriate material includes questions about past, current, and future CD-R devices. Asking for installation help or advice on what to buy is appropriate, as are questions about related hardware like SCSI adapters and CD-ROM drives. Some related newsgroups are:
news:comp.sys.ibm.pc.hardware.cd-romnews:comp.publish.cdrom.software is for discussions about software used to prepare material for and create CDs and CD-ROMs. Questions about how to do things with a specific piece of software belong here, as do "the CD-R software from XXX won't recognize my drive", and "does a program exist that does YYY". Some related newsgroups are:
news:comp.sys.ibm.pc.hardware.storage
news:comp.sys.ibm.pc.hardware.systems
news:alt.comp.periphs.cdr
news:comp.periphs.scsi
news:alt.cd-rom
news:linux.apps.cdwrite
news:alt.cd-romnews:comp.publish.cdrom.multimedia is for discussions about creating multimedia products on CD-ROMs. Questions about multimedia authoring software belong here, as do most production-type questions, e.g. "where can I go to get my CD pressed with jewel cases and glossy inserts?" Related newsgroups are:
news:linux.apps.cdwrite
news:comp.multimediaPlease try to keep cross-posting to a minimum. Broadcasting questions to 3 or 4 related newsgroups will increase the noise level and probably won't get you more answers.
news:rec.video.desktop
news:rec.video.professional
news:rec.photo.digital
news:misc.education.multimedia
Some general rules apply to all of the comp.publish.cdrom.* groups:
(1) Piracy of CD-ROM software or CDs: CD recorders can be used to make copies of copyrighted material, and while backups of data are legal, making or accepting copies from others most likely isn't. Whatever your opinion of the matter, software piracy and other copyright violations are illegal in most countries in the world, so requests and/or advertisements for pirated material should be kept off the newsgroup. Also, please don't start or participate in a debate about whether or not software piracy is bad. There have been hundreds of such debates over the past several years, and the only thing that either side has managed to prove is that piracy debates are a tremendous waste of time.
(2) Personal CD-R hardware and software sales: strictly speaking, these groups aren't appropriate for selling off your old hardware or software. Such things are best left in misc.forsale.computers.*, ba.market.computers, and related groups. Since many readers are in the market for new hardware, a limited number of clearly marked articles are tolerated. The common Usenet convention is to use "FS: HP4020i $400 obo" for "For Sale" messages and "WTB: HP4020i" for "Want To Buy" messages.
(3) CD-R product advertising: these groups by their nature are somewhat commercial. Many readers are in the market for new hardware or CD-R media, and for this reason a *limited* amount of retail/wholesale advertising is tolerated but discouraged. If you *clearly* mark your postings as advertisements, you will get relatively few complaints. Posting frequent and useless followups just to broadcast your 20-line signature will get you flamed and subsequently ignored. Feel free to send mail to people who post questions about product pricing and availability, but please don't create mailing lists and broadcast to everyone who posts.
(4) Other advertising: while it's certainly the case that most or all of the readers have a CD-ROM drive on a computer, the same could be said of almost every person reading news from a home computer today. Please keep ads in newsgroups that are more appropriate. Advertising the latest educational, game, or adult CD is inappropriate for these groups, as are "hot new Cyrix 686 PC" posts. Subtle attempts to advertise web sites ("golly, this looked really neat, so I thought I'd tell everyone") are more obvious than you might think.
(5) Spam: you cannot make money fast. That's life, get used to it. If the message involves putting your name at the top of a list of 5 or 10 people, don't post it. If it has an 800 or 888 number that a reader would call to hear more about your unique business opportunity, don't post it.
(6) Job postings: looking for job candidates on these newsgroups is a tolerated but generally futile exercise. Most of the readers are looking for or offering help on CD-Rs, not searching for a job. Try one of the other groups, like misc.jobs.offered.
(7) Binaries: as with most Usenet newsgroups, posting binary files (large or small) is inappropriate. If you want to make a binary file available to Usenet readers, send it to an appropriate alt.binaries newsgroup, and just post a pointer to it in the other group(s).
One final note: bear in mind that these groups are read by people all over the world. If you're looking for local retailers, be sure to specify what "local" is for you. Posting in English is the best way to ensure that you will get a response, but the readership is diverse enough that you will likely get a reply no matter what language you use. If you want to quote prices, specify the currency to avoid confusion (e.g. US$300 or CAN$300 or Y30000 or ...).
The first thing to do is look at the web pages for the products you're using. Sometimes there will be software or firmware updates, or pages with information on common problems. Doing a web search or scanning through news archives on servers like Google Groups (http://www.google.com/) will often turn up relevant material.
If you don't find anything, calling or sending an e-mail message to the technical support department for the product that is giving you trouble is a good second step. If you want to contact other users, posting a message to one of the Usenet newsgroups is a reasonable thing to do.
You will get faster, more accurate responses to questions if you include enough detail in your mail message or news posting. For most problems having to do with recording, you need to specify:
Whenever possible, the FAQ tries to use the correct spelling and terminology. Errors should be reported to the FAQ maintainer, but bear in mind that I don't modify the contents of quoted material, the names of products, or the titles of articles and web pages.
Some common mistakes are:
(1) Writing "CDROM" instead of "CD-ROM". It should be CD-ROM, CD-R, CD-RW, and CD-DA, not CDROM, CDR, CDRW, CDDA.
(2) Writing "disk" instead of "disc". The words have the same meaning, but are spelled differently in different countries, just like "color" and "colour". By convention, CDs are called "discs", while hard drives and floppies are called "disks". "Disc-to-disc" copies are different from "disk-to-disc" and "disc-to-disk" copies!
(3) Referring to a sector as a "frame". On a CD, the basic allocation unit visible outside the firmware is the 2352-byte sector (sometimes called a "block"). A "frame" is a structure at a lower level. There are 24 bytes in a frame, and 98 frames in a sector (24*98 = 2352).
Not really. In an effort to keep the FAQ fair and impartial, I don't accept advertising. Vendors with relevant products can have URLs added to appropriate sections of the FAQ. Vendors without URLs for their products aren't usually listed.
Products that solve specific problems, such as recovering data from damaged discs, repairing scratches, or removing pops and clicks from digitized audio tracks, will be listed under the appropriate topic. CD recording software and hardware vendors can get their own sub-section. Vendors that don't fit in a specific category will be listed in section (8).
I'm not set up to act as a mail server, but some other places are. You can request a copy of the FAQ from rtfm.mit.edu's mail server like this:
To: mail-server@rtfm.mit.edu
Subject: foo
send faqs/cdrom/cd-recordable/part1The mail server breaks each part into smaller pieces, so you will end up with about a dozen mail messages when all is done.
send faqs/cdrom/cd-recordable/part2
send faqs/cdrom/cd-recordable/part3
send faqs/cdrom/cd-recordable/part4
You can get a full FAQ list on "accessing the Internet through e-mail" from http://www.faqs.org/faqs/internet-services/access-via-email/ or by mail request:
To: mail-server@rtfm.mit.edu
Subject: foo
send usenet/news.answers/internet-services/access-via-emailDon't put anything else in the body of these messages; just one or more "send" lines. The "subject" line is ignored.
These are intended to be brief (if somewhat incomplete) answers to basic questions. More detailed information can be found later in the FAQ. For example, section (1-5), "How much can they hold?", is answered in far more detail in section (7-6).
CD-R is short for "CD-Recordable". Recordable CDs are WORM (Write Once, Read Multiple) media that work just like standard CDs. The advantage of CD-R over other types of optical media is that you can use the discs with a standard CD player. The disadvantage is that you can't reuse a disc.
A related technology called CD-Rewritable (CD-RW) allows you to erase discs and reuse them, but the CD-RW media doesn't work in all players. CD-Rewritable drives are able to write both CD-R and CD-RW discs.
All CD recorders can read CDs and CD-ROMs, just like a standard CD-ROM drive.
The CDs you buy in a store are pressed from a mold. CD-Rs are burned with a laser. They may look different (often green, gold, or blue instead of silver), they're less tolerant of extreme temperatures and sunlight, and they're more susceptible to physical damage. Whether CD-Rs or pressed CDs last longer is difficult to answer.
While they're not physically identical, they work just the same. Some CD players and CD-ROM drives aren't as good at reading CD-R and CD-RW discs as they are at reading pressed CDs, but by and large they work just fine.
By the way, you can't record on pressed discs, so you might as well throw out all those AOL CD-ROMs you've been accumulating. Buying a bunch of old CDs in the hopes of writing new stuff onto them is a bad idea. For similar reasons you can't record on DVD media, not even DVD-R and DVD+RW, unless your drive explicitly supports the DVD formats. You have to buy blank CD-R or CD-RW media.
Yes. You can create CD-ROMs from data on your hard drive, and you can create new audio CDs from anything you can record into a WAV or AIFF sound file. With an audio-only CD-Recorder, which hooks up to your stereo system instead of your computer, you can record directly from CD, cassette, DAT, or whatever.
The CD-ROMs you produce will play in ordinary CD-ROM drives, and the audio CDs you create will work in your home or car CD player.
Writing to CD-Rs and CD-RWs requires a CD recorder. You can't write CDs with an ordinary CD-ROM drive.
One of the more popular things to do with a CD recorder is make copies of old cassettes and LPs. See section (3-12) for information about this.
Yes, both audio and data CDs can be duplicated. You can even create audio CDs that are compilations of other audio CDs (perhaps a personal "best of" disc).
Bear in mind that most CDs are protected by copyright laws.
About 74 minutes of audio, or about 650MB of data.
Some CD-R blanks can hold 80 minutes of audio, or about 700MB of data.
See section (7-6) for more info.
Yes and no. The process can be a bit more involved than that, and requires software that (usually) comes bundled with the drive.
With "packet writing" software, and a recorder that supports it, you can treat a CD-R or CD-RW disc like a floppy. On a CD-R you can only write to each part of the disc once, so deleting files doesn't gain any space. There are other limitations as well.
With more traditional software -- necessary if you want broad compatibility -- you usually end up writing everything to the disc all at once. When you're doing the writing you can't interrupt the drive, and you can't reclaim the space you've used. If you want to write your files in smaller bunches, you lose a fair bit of space every time you stop and start again.
Nothing. This FAQ is about CD-R and CD-RW, and only crosses over into DVD when the two technologies rub up against each other.
To learn more about DVD, see section (2-14) and check out the DVD FAQ at http://www.dvddemystified.com/dvdfaq.html. For DVD recorders, check out the Usenet newsgroup alt.video.dvdr and perhaps rec.video.dvd.tech.
Not directly. CD and DVD are very different formats, so you can't write DVDs with your CD recorder. You may be able to convert the contents into a lower-quality format though. Be wary of scams. See section (3-49).
There are devices now that can record both DVD-R and CD-R. Those are usually advertised as "DVD recorders", not "CD recorders".
I don't know. I don't track prices. There are web sites dedicated to finding the lowest prices, and you can do a little research with a web browser, starting perhaps with the vendors listed in section (8-3).
Yes, from the manual that comes with your recorder and software. There's no information of this type in the FAQ because there are far too many permutations of hardware and software, and the instructions would have to be updated with every new release of the software.
Yup. You can download MP3s, write them to a CD, and play it in anything that handles audio CDs. In fact, many of the popular CD recording programs will decode the MP3s for you.
It's also possible to take songs from a CD and convert them to MP3s for use in an MP3 player.
Section (3-27) has more details.
There are some good glossaries on the web. Try these:
You only need "music" blanks if you have a "consumer" stand-alone audio CD recorder. If you have a recorder attached to your computer or a "professional" deck then the "music" blanks will work no better or worse than "data" blanks.
See section (7-17) for details.
This FAQ contains a great deal of information, but it's geared toward answering specific questions rather than providing a general education. Some of the other net resources are more like a tutorial than a Q&A list, and may provide a better starting point.
Mike Richter has a primer on CD-R at http://www.mrichter.com/.
Roxio has some good information at http://www.roxio.com/en/support/.
If you're new to CD recording and are feeling a little lost, you may want to buy a book on the subject. Try one of these:
You may be reading an out-of-date copy of the FAQ. Some sites like to make a copy of the FAQ with the version, date, and contact information stripped off the top (in violation of section (0-1)), which makes it hard to tell when it was last updated. The FAQ is updated about once a month, and the most recent version is always available from http://www.cdrfaq.org/.
If you are reading the current version, either the section hasn't been updated in a while (check the date in the section), or something has slipped past me.
If you want news articles updated daily, try the sites in section (8-4).
CD fundamentals.
From _The Compact Disc Handbook, 2nd edition_ by Ken Pohlmann, 1992 (ISBN 0-89579-300-8):
"Write-once media is manufactured similarly to conventional playback-only discs. As with regular CDs, they employ a polycarbonate substrate, a reflective layer, and a protective top layer. Sandwiched between the substrate and reflective layer, however, is a recording layer composed of an organic dye. .... Unlike regular CDs, a pre-grooved spiral track is used to guide the recording laser along the spiral track; this greatly simplifies recorder hardware design and ensures disc compatibility."
Your basic CD-R is layered like this, from top to bottom:
[optional] labelYes, it's real gold in "green" and "gold" CDs, but if you hold a CD-R up to a light source you'll notice that it's thin enough to see through (the gold layer is between 50 and 100nm thick). Something to bear in mind is that the data is closest to the label side of the CD, not the clear plastic side that the data is read from. If the CD-R doesn't have a hard top coating such as Kodak's "Infoguard", it's fairly easy to scratch the top surface and render the CD-R unusable.
[optional] scratch-resistant and/or printable coating
UV-cured lacquer
Reflective layer (24K gold or a silver-colored alloy)
Organic polymer dye
Polycarbonate substrate (the clear plastic part)
A pressed CD has raised and lowered areas, referred to as "lands" and
"pits", respectively. A laser in the CD recorder creates marks in the
disc's dye layer that have the same reflective properties. The pattern
of pits and lands on the disc encodes the information and allows it to be
retrieved on an audio or computer CD player. See section (2-43) for
specifics.
Discs are written from the inside of the disc outward. On a CD-R you can verify this by looking at the disc after you've written to it. The spiral track makes 22,188 revolutions around the CD, with roughly 600 track revolutions per millimeter as you move outward. If you "unwound" the spiral, it would be about 3.5 miles long.
The construction of a CD-RW is different:
[optional] labelSee the net references section for pointers to more data (especially http://www.cd-info.com/). You can find some nice drawings at http://www.nswc.navy.mil/cosip/nov97/cots1197-2.shtml and http://www.pctechguide.com/09cdr-rw.htm.
[optional] scratch-resistant and/or printable coating
UV-cured lacquer
Reflective layer
Upper dielectric layer
Recording layer (the part that changes form)
Lower dielectric layer
Polycarbonate substrate (the clear plastic part)
A quick summary of standards and commonly used identifiers:
See http://www.licensing.philips.com/ if you want to buy copies of the standards. They're not cheap! You can download some of them from http://www.ecma.ch/. ECMA-119 describes ISO-9660, and ECMA-130 sounds a lot like "yellow book" if you say it slowly.
For SVCD, see http://www.iki.fi/znark/video/svcd/overview/. The discs are a modified White Book format, using a 2x player and variable bit rate MPEG-2 instead of MPEG-1 at 1x like VCD.
For HDCD, see http://www.hdcd.com/. The discs are in Red Book format, but the low bit of the audio has additional information encoded in it. They sound good on a standard CD player, and better on an HDCD player.
SACD isn't really a CD format. It can have a Red Book compliant layer that is read by standard CD players, but to get the high-fidelity benefits you need a special player.
You can usually tell by looking at the packaging and/or the disc itself:
There are a few references to Compact Disc MIDI, or CD-MIDI.
See (4-46) for some comments on High Speed CD-RW.
Copy protection (sometimes erroneously referred to as "copyright protection") is a feature of a product that increases the difficulty of making an exact duplicate. The goal is not to make it impossible to copy -- generally speaking, that can't be done -- but rather to discourage "casual copying" of software and music.
The goal is *not* to conceal information from prying eyes; see section (3-19) for information on encrypting data on a CD-ROM.
A separate but related issue is "counterfeit protection", where the publisher wants to make it easy to detect mass-produced duplicates. An example of this is Microsoft's placement of holograms on the hubs of their CD-ROMs. There are full CD pressing plants dedicated to creating counterfeit software (the worst offender being mainland China), so this is a serious concern for the larger software houses.
Copy protection on CD-ROMs used to be rare, but as the popularity of CD recorders grew, so did the popularity of copy protection. A large percentage of games released in the past few years have been protected.
A more recent innovation is copy protection for audio CDs, inspired by the rise of MP3 trading over the Internet. This is more difficult to do, because the protection must allow correct behavior on a CD player but altered playback when being read by a CD-ROM drive. The best that can be accomplished is to force the user to play the music in an analog format and then re-digitize it, resulting in an imperfect reproduction.
The article at http://news.cnet.com/news/0-1005-201-7320279-0.html is a nice introduction to the issues.
Some people have questioned whether copy protection is legal. In some countries it may not be. In the USA, the law allows "fair use" of copyrighted material, but does not require that the content provider make it easy for you to do so. So while making a copy of a song for your own private use may be legal, there is nothing in the law that requires the publisher to make the material available in an unprotected format. Copy protection has been around for many years -- some of the schemes employed on the Apple II were remarkably elaborate -- and has never been challenged on legal principle.
See http://overclockers.com/tips907/ for an article about why "fair use" is a legal right rather than a constitutional right in the USA, and what that means to you. The article also has some interesting quotes from the courts regarding the DMCA and DeCSS, notably this one: "We know of no authority for the proposition that fair use, as protected by the Copyright Act, much less the Constitution, guarantees copying by the optimum method or in the identical format of the original." In other words, arguing that "fair use" means the publisher must allow you to make a perfect digital copy (as opposed to a lower-quality digital or analog copy) is without merit.
The next sections discuss data and audio individually.
There are several approaches. An article with a good overview of some popular protection technologies can be found at http://www.tomshardware.com/storage/02q2/020617/index.html. Another source is the "CD Protections" articles on http://www.cdmediaworld.com/hardware/cdrom/cd_protections.shtml.
For anyone interested in protecting their own discs: don't bother. Copy protection, on the whole, does not work. If you have a major application, such as a game or CAD package, you may want to consider one of the commercially licensed schemes listed later, or (heaven forbid) the use of a dongle. In general, though, if the disc can be read, then the contents can be copied. If you don't want somebody to make a copy of your stuff, then you'd better encrypt it (3-19).
A simple and commonly seen technique is to increase the length of several files on the CD so that they appear to be hundreds of megabytes long. This is accomplished by setting the file length in the disc image to be much larger than it really is. The file actually overlaps with many other files. So long as the application knows the true file length, the software will work fine. If the user tries to copy the files onto their hard drive, or do a file-by-file disc copy, the attempt will fail because the CD will appear to hold a few GB of data. (In practice this doesn't foil pirates, because they always do image copies. And, no, none of the standard software provides a way to create such discs.)
One possible implementation, given sufficient control over the reader and mastering software, is to write faulty data into the ECC portion of a data sector. Standard CD-ROM hardware will automatically correct the "errors", writing a different set of data onto the target disc. The reader then loads the entire sector as raw data, without doing error correction. If it can't find the original uncorrected data, it knows that it's reading a "corrected" duplicate. This is really only viable on systems like game consoles, where the drive mechanism and firmware are well defined. This can be defeated by doing "raw" reads.
A more sophisticated approach is to write special patterns of data to the disc. The stream of data that results, after EFM encoding, is difficult for some recorders to reproduce successfully, apparently because they don't choose correct values for the merging bits. This is often referred to on web sites as "writing regular EFM patterns" or "weak sectors". See section (2-43) for details on EFM.
A less sophisticated -- and no longer effective -- method is to press a silver CD with data out beyond where a 74-minute CD can write. Copying the disc used to require hard-to-find CD-R blanks, but now it's easy to use an overburned 80-minute disc (sections (3-8-1) and (3-8-3)).
The approach some PC software houses have taken is to use nonstandard gaps between audio tracks and leave index marks in unexpected places. These discs are uncopyable by most software, and it may be impossible to duplicate them on drives that don't support disc-at-once recording (see section (2-9)). With the right reader and software, though, this isn't much of a problem either.
A method that enjoyed some popularity was non-standard discs with a track shorter than 4 seconds. Most recording software, and in fact some recorders, will either refuse to copy a disc with such a track, or will attempt to do so and fail. A protected application would check for the presence and size of the track in question. Some recorders may succeed, however, so this isn't foolproof. (In one case, a recorder could write tracks that were slightly over three seconds, but refused to write tracks that were only one second. There may be a limit below which no recorder will write.) In such cases, the pirates need to remove the explicit check from the software itself.
Putting multiple data tracks interleaved with audio tracks on a CD will confuse some disc copiers. However, it's difficult to actually use the data on those additional tracks.
Sometimes the copy of a disc will have a different volume label. This usually only happens with file-by-file copies, not disc image copies, so checking the disc name is marginally useful but not very effective.
Modifying the TOC so that the disc appears to be larger than it really is will convince some copy programs that the source disc is too large.
Some of the fancier technologies use non-standard pit geometry that cause players to read the data differently on consecutive attempts. Sometimes the player sees a "1", sometimes a "0". If, when reading the track, the CD-ROM drive sees different data each time, the software knows that the disc is an original. A duplicate disc will return the same data reliably. (So too will some CD-ROM drives... this technology is not without problems.)
Some programs will examine the disc to try to determine if it's a CD-R. This doesn't work on all readers, and it's possible to disguise discs, so this isn't very effective.
CloneCD (section (6-1-49)) can copy many copy protected discs without trouble, given the right combination of reader and writer. Its main feature is "raw" reads and writes, which not all drives support.
The Laserlok system from http://www.diskxpress.com/ claims to be able to prevent unauthorized disc duplication at a low cost. It can be copied by CloneCD.
An unrelated product called LaserLock, from MLS LaserLock International (http://www.laserlock.com/) has similar features. It can be copied by CloneCD.
TTR Technology's DiscGuard (http://www.ttr.co.il/ or http://www.ttrtech.com/ claims to be able to write a signature onto pressed CDs and CD-Rs that is detectable by all CD-ROM drives but isn't reproducible without special hardware. A program could use this for copy protection by checking for the presence of the signature, and refusing to run if it's not there.
Sony DADC is promoting a simliar product called Securom. Some information is at http://www.sonydadc.com/hotnews/secu_fra.htm.
Yet another variant is C-Dilla's SafeDisc. They were bought by Macrovision (http://www.macrovision.com/). Their more recent product, SafeDisc 2, was the first to feature "weak sectors".
Yet another variant is CD-Cops from Link Data Security (http://www.linkdata.com/).
The challenge here is to create a disc that will play on a standard audio CD player but be difficult to copy or "rip" into an MP3. The techniques making headlines in mid-2001 were developed by Macrovision (2-4-3) and SunnComm (2-4-4).
The earliest form of audio CD copy protection was SCMS. This only works on recorders that support SCMS, specifically consumer-grade stand-alone audio CD recorders. "Professional" recorders, and recorders that attach to computers, do not support SCMS. See section (2-25).
Some CDs used a damaged TOC (Table of Contents -- see section (2-27)) that confused some CD-ROM drives and ripping software. More recent schemes attempt to modify the audio samples in ways that confuse CD-ROM drives into playing static. The next few sections describe these approaches in detail.
For a list of suspected copy-protected discs, and some tips on what you can do to let the industry know that the protection isn't appreciated, see http://www.fatchucks.com/corruptcds/.
Many forms of copy protection violate the CD-DA standard, and so the discs aren't allowed to use the official CD logo art. However, many CDs don't have the logo anywhere, so its absence doesn't prove anything.
A paper entitled "Evaluating New Copy-Prevention Techniques for Audio CDs" by J.A. Halderman (available only in PostScript format) can be found at http://crypto.stanford.edu/DRM2002/halderman_drm2002_pp.ps. The paper was submitted to the 2002 ACM Workshop on Digital Rights Management (http://crypto.stanford.edu/DRM2002/prog.html).
Incidentally, if you're convinced that record companies and artists are
raking in huge piles of cash from every CD they sell, you might want to
take a look at an Electronic Musician article that talks about where the
money comes from and where it goes. See:
http://industryclick.com/magazinearticle.asp?magazineid=33&releaseid=9554&magazinearticleid=132835&SiteID=15
(You may need to use IE; Netscape 4.7 for Linux couldn't view the site.)
Interesting figures: only about 16% of CDs sold make enough money for the publishers to break even. The ones that do make enough money have to pay for the rest. For the recording artists, only about 3% sell enough music to get any royalties. With figures like these, it's not surprising that the industry is taking steps to combat piracy.
For more news & commentary, see:
In the first part of the year 2000, TTR Technologies announced a product called MusicGuard (http://www.MusicGuard.com/) that claimed to prevent duplication of audio CDs. The product was withdrawn, but the technology has resurfaced in mid-2001 as a product called SafeAudio from Macrovision (http://www.macrovision.com/).
The basic idea is to create samples that sound like bursts of static, and scramble the ECC data around to make it look like an uncorrectable error. Audio CD players will interpolate the samples during playback, but CD-ROM drives doing digital audio extraction generally won't. The result is a disc that plays back correctly on a CD player, but won't "rip" or copy correctly on a CD-ROM drive.
Some relevant sites and news articles:
The digital path requires reading the "raw" audio samples off of the disc, possibly modifying the data (e.g. changing the byte ordering) into something appropriate for the sound card, and then writing them to the sound device. Until a few years ago, most CD-ROM drives did this very poorly, in part because the analog and digital data paths were logically distinct in the designers' minds. Audio CDs used the audio path, data CD-ROMs used the digital path, and while you *could* send audio over the digital path there didn't seem to be much value in doing so. (See section (2-15) for some additional notes.)
What Macrovision appears to be exploiting is the different handling of uncorrectable errors in audio samples on the digital path vs the analog path. When playing an audio CD in a CD player or CD-ROM drive, the analog path is used. This path deals with uncorrectable (E32) errors by examining the samples that come before and after the error, and interpolating between them. On a scratched-up CD, this means that, while you may not be hearing the exact samples that were originally recorded, you won't notice any glitches because they're smoothed over. This feature is definitely not something you'd want on a data CD-ROM -- interpolating pieces of your spreadsheet is not going to help you.
In most CD-ROM drives, reading an audio sector with digital audio extraction is handled the same way that reading a data sector is: uncorrectable errors are left alone. Instead of getting interpolated samples, you get to hear the original, scratched-up audio. This is why some CDs will play back just fine on your computer, but will come out all scratched up when you extract them with the same drive. The errors are there either way, but when using a desktop CD player the errors have been smoothed over by the logic in the analog output path.
Some drives may use interpolation during DAE at lower speeds. If so, it should be possible to "rip" a track from a copy-protected disc by reducing the extraction speed to 1x.
Some people have suggested that software could be used to perform the interpolation on extracted music, stripping out the bits that the music companies added in. The trouble with this approach is that, once the data has been extracted, the CIRC encoding is no longer visible. It may not be easy to tell where the glitches are. For example, it should be possible to create a low-level but rhythmic distortion that will be noticeable, annoying, and difficult to identify automatically.
(It's possible that any software specializing in defeating the copy protection would run afoul of the DMCA (Digital Millenium Copyright Act), and the authors subject to fines and criminal prosecution. Come to think of it, the preceeding discussion might be illegal. For more information about the DMCA, see http://www.eff.org/.)
How can you get a "clean" copy of a protected disc? There are four basic approaches, in order of least to most desirable:
(1) Record directly from the analog outputs of the drive, feeding the sound into a sound card or outboard A/D converter. Some fidelity will be lost when converting from digital to analog and back again, which is what the industry is counting on.
(2) It should be possible to play the disc on a CD player with an S/PDIF connector, and get error-interpolated digital output. If played into a digital sound card or a CD recorder with an S/PDIF input, it should be possible to capture an exact copy of the original. Of course, it has to be done at 1x, and the track breaks may have to be added manually, making it a potentially tedious affair. This might be avoidable on a CD-R "dubbing deck", but inexpensive models will add SCMS to the set of things to worry about. Don't forget that generation loss is possible with CDs, especially if you record from CD-Rs (due to their higher BLER rate), so copying to CD-R and then extracting from CD-R requires some care. See section (3-18).
(3) Some drives support an extension described in recent versions of the ATA/ATAPI and SCSI MMC specifications. This extension to the "READ CD" command returns a set of flags indicating which bytes in an audio block were not corrected at the C2 level (section (2-17). An audio extraction application with access to this information could do its own interpolation across errors. Some applications already make some use of this feature; see http://www.feurio.com/English/faq/faq_vocable_c2error.shtml. The "drive check" feature of cdspeed (section (6-2-11)) reports on whether or not a drive is capable of returning "C2 pointers".
(4) A CD-ROM drive with logic that interpolates uncorrectable errors during DAE would allow copying and ripping with no additional effort required.
The success or failure of audio CD copy protection hinges upon two factors:
how effective is it at preventing "casual copying", and what sort of
problems do the legitimate owners of audio CDs encounter when playing
their discs? Macrovision claims that their "golden ear" listeners were
not able to tell the difference, though the test might be biased if the
folks with the shiny lobes were using high-end CD players that did an
especially good job of concealing uncorrectable errors.
A legitimate technical concern is that the copy protection reduces the effectiveness of the error correction. Because some percentage of ECC is now required for proper playback on a *clean* disc, the odds of scratches and fingerprints causing audible degredation are increased. In practice, if the "static" samples are relatively few and far between, the difference would be statistically insignificant.
One last piece of advice: do not assume that any disc that doesn't extract cleanly is copy-protected. There have been many, many postings on message boards from people who think they have found a protected disc, or how some specific piece of software can defeat the protection. Start with the more common reasons: the disc is dirty, the disc was poorly made, your CD-ROM drive is not that great at audio extraction, you're using software that isn't the best. There are many reasons why ripping an audio track might fail. People have been having trouble getting clean audio for years. See section (3-3) for some advice if you're having trouble.
Certain web sites (notably cdfreaks.com) have been reporting that a replacement CDFS.VXD will fix everything. However, doing the audio extraction in a VXD instead of an EXE makes no difference. So far, none of the sites that have claimed victory list a single SafeAudio-protected disc that was copied, most likely because -- at the time this was written -- there weren't any discs known to use SafeAudio. (This phenomenon is not unheard-of; Sega's Dreamcast discs were widely reported to be copyable by a means that was quickly determined to be utterly ridiculous.) If the widely-touted CDFS.VXD is in fact a hijacked Plextor driver, then it may well use technique #3 mentioned above, but would only work on a drive that supported the extended READ CD feature.
SunnComm (http://www.sunncomm.com/) has a product called "MediaCloQ". It was used to protect the album _A Tribute to Jim Reeves_ by Charley Pride in mid-2001. The results were inconclusive: clean versions of the tracks appeared on the net, but SunnComm claimed they came from an unprotected disc released on Australia. Their plan was to alleviate "fair use" concerns by allowing users to download MP3 versions of the songs after they registered the original. Some articles:
The idea behind this protection is to make it hard for CD-ROM drives to identify the disc as being an audio CD. The disc is multisession, and uses a hacked TOC, so track rippers and disc copiers have trouble dealing with it. SunnComm hasn't publicly stated any details.
In August 2001, SunnComm announced v2.0 of their product, but didn't provide specific details.
Some personal notes on SunnComm's protection of the Charley Pride disc,
including the steps I took to get a clean copy:
The packaging is labeled with the SunnComm logo, and states, "This audio CD is protected by SunnComm(tm) MediaCloQ(tm) Ver 1.0. It is designed to play in standard audio CD players only and is not intended for use in DVD players." However, my DVD player was able to play the disc after overcoming some initial confusion.
The disc itself has an unusual construction. There is a heavy band at about the point where the music stops, and thin bands between tracks. These appear to be purely decorative (and, I'm told, increasingly common on non-protected discs). Some images are available on http://www.fadden.com/cdrpics/.
A computer running Win98SE with a Plextor 40max CD-ROM drive saw the disc as having two sessions and 16 data tracks. My CD player only saw 15 audio tracks. This feature alone makes the disc difficult to rip or copy, because the software doesn't see any audio tracks, and a CD-R copy would be full of tracks that even a CD player would see as data. Another machine, with a Plextor 12/20 and a slightly different set of software, seemed to have a lot of trouble figuring out what the disc was. It eventually sorted things out, but I get the sense the disc has been tweaked in ways that confuse the drive firmware.
I tried using "Session Selector" to select the first session and then access the tracks. This resulted in a Plextor 8/20 CD recorder becoming unusable until a reboot. I'd guess the firmware got confused.
The next thing I tried was to crank up CDRWIN v3.7a (section (6-1-7)), and extract some tracks using my Plextor 12/20. No dice -- the display showed 15 unselectable tracks and 1 MODE-2 data track.
Next, I tried the "Extract Disc/Tracks/Sectors" function, selected "Extract Sectors", chose "Audio-CDDA (2352)" for the data type, and entered a nice range (0 to 300000, where each audio sector is 1/75th of a second). This choked when trying to read starting at block 173394, so I tried again stopping at 173390. This resulted in a rather large WAV file, which I opened with Cool Edit -- revealing the entire contents of the disc, plain and clear. Playback revealed no audible defects.
I believe this worked because the sector extraction function ignores track and session boundaries, and just pulls the blocks straight off. Losing the track markers is annoying, but it's easy to add them back with something like CDWave (section (6-2-16)).
(FWIW, this same approach did *not* work for the _My Private War_ disc with the damaged TOC, described in (2-4-2). It would probably not be of help with a SafeAudio disc either.)
"zEEwEE" came up with a complicated but enlightening scheme for side-stepping the protection on discs with damaged second TOCs. It has the advantage of allowing you to use standard tools, such as Exact Audio Copy ( section (6-2-12)), which keeps the track breaks and can do fancy tricks to get the best extraction quality. See http://cdprot.cjb.net/. [ I'm told the disc used as an example was actually protected with Midbar Tech's Cactus Data Shield 100, not MediaCloQ. ] The method involves making the outer rim of the disc unreadable to the CD-ROM drive. It appears you can use dry erase markers instead of adhesive stickers for the procedure, which is good since an adhesive label might peel up and damage your drive. This method, first posted in August of 2001, resulted in a flurry of media attention in May of 2002.
Midbar Tech Ltd (http://www.midbartech.com/) appears to have two different schemes under the "Cactus Data Shield" brand. (The web site shows three now: CDS100, CDS200, and CDS300.) The first uses a non-standard TOC. The position of the lead-out and the length of the last track were tweaked, resulting in a disc that appears to be only 28 seconds long. The alterations didn't confuse all CD-ROM drives, and it has been reported that some Philips CD players couldn't play the discs. BMG Entertainment reportedly tried it and abandoned it.
In late 2001, Midbar Tech announced a different approach. A US patent (http://www.delphion.com/details?&pn=US06208598__) describes the invention.
The approach appears to involve inserting frames of bogus control information into a relatively constant part of the CD audio stream. During playback, the extra frames are skipped. A disc copy or digital stream on an S/PDIF output will include the bogus frames, and when written to CD-R the extra control information won't be included. The result is bad samples that only appear in copies.
News articles:
No specific disc titles have been announced, but Sony has reportedly released a few titles in eastern Europe that use this.
Some personal notes on the early version (CDS100?) of the Cactus Data
Shield: I bought a copy of _My Private War_, by Phillip Boa & The Voodoo
Club, from an online retailer. The disc is labeled "Kopiergeschützte CD -
nicht am pc abspielbar" which translates literally to "copy-protected CD
- not at the PC playable". Supposedly this is one of the BMG discs that
was protected with Midbar's first product.
The Plextor Plextools utility saw it as a single-session audio CD with 13 tracks, but when I asked it to play the disc it only saw the first 28 seconds of the first track, and stopped after playing just that much. My Panasonic CD "boom box" also thought the disc was only 28 seconds long, but it happily played past that point, and would let me select any track.
The page at http://uk.eurorights.org/issues/cd/docs/natimb.shtml has an analysis of the CD _White Lilies Island_ by Natalie Imbruglia.
http://www.cdrinfo.com/Sections/Articles/Specific.asp?ArticleHeadline=Cactus%20Data%20Shield%20200&index=0 has a very thorough examination of a CDS200 disc. Recommended reading.
This was used to protect promotional copies of the Michael Jackson single "You Rock My World". See http://www.key2audio.com/ for product information.
News articles:
The technology is designed to make the discs unrecognizeable to CD-ROM drives. According to the web pages, the product is licensed through Sony DADC.
The "Duolizer" system splits music into two pieces. The bulk of the music is on the CD, but a small but essential piece is streamed from a secure server over the Internet. The idea is to allow music publishers to distribute songs to the media and retail outlets ahead of scheduled releases. This was a response to songs appearing in MP3 form on the Internet before the CDs went into distribution.
See http://www.bayviewsystems.com/solutions/duolizer.htm for product info.
News articles:
This scheme can't be used for general CD protection, because if the music can be played on a computer at all, it can be captured with a program like Total Recorder (http://www.HighCriteria.com/). It will be reasonably effective for promotional copies of songs, though, where the goal is to prevent people from walking away with copies of the discs.
As an added bonus, because the music is streamed from a central location, it could have a digital watermark added. If (say) somebody at a radio station made an MP3 copy, it might be possible to trace the source of the MP3 file back to the source. There is nothing on the product pages to suggest that such a scheme is currently in place.
Sany has joined the growing list of companies to announce CD copy protection. It's not clear if this is their own scheme or one licensed from another company.
News articles:
The disc has an embedded secure micro (like a smart card) that is activated when the laser light strikes a photodetector. The light is converted to electrical impulses, the impulses drive the chip, and if all goes well the results are presented to the drive via an embedded light-emitting diode.
Making an exact duplicate of the disc would be very difficult. It's unclear whether this technology actually makes it harder to get a working copy of the contents. The scheme seems to essentially be a combination of an "uncopyable" disc and a hardware dongle, both of which have been around for years (neither of which have brought an end to piracy).
The company's web site is http://www.doc-witness.com/.
News articles:
A session is a recorded segment that may contain one or more tracks of any type. The CD recorder doesn't have to write the entire session at once -- you can write a single track, and come back later and write another -- but the session must be "closed" before a standard audio CD or CD-ROM player will be able to use it. Additional sessions can be added until the *disc* is closed or there's no space left.
Multisession writing was first used on PhotoCD discs, to allow additional pictures to be appended. Today it's most often used with "linked" multisession discs, and occasionally for CD-Extra discs. These require a bit more explanation.
When you put a data CD into your CD-ROM drive, the OS finds the last closed session on the disc and reads the directory from it. (Well, that's how it's supposed to work. Depending on your operating system and CD-ROM drive, you may get different results.) If the CD is ISO-9660 format - which it almost certainly is unless it's a Macintosh CD written in HFS - the directory entries can point at any file on the CD, no matter which session it was written in.
Most of the popular CD creation programs allow you to "link" one or more earlier sessions to the session currently being burned. This allows the files from the previous sessions to appear in the last session without taking up any additional space on the CD (except for the directory entry). You can also "remove" or "replace" files, by putting a newer version into the last session, and not including a link to the older version.
In contrast, when you put an audio CD into a typical CD player, it only looks at the first session. For this reason, multisession writes don't work for audio CDs, but as it happens this limitation can be turned into an advantage. See section (3-14) for details. This limitation does *not* mean you have to write an entire audio CD all at once; see section (2-9) for an overview of track-at-once writing.
(Some audio CD players do seem to be able to recognize all of the tracks on a multisession audio disc. Most do not. The only way to know for sure is to try and see. If you are planning to give an audio CD you create to others, it would be wise to write it in a single session.)
Note that mixing MODE-1 (CD-ROM) and MODE-2 (CD-ROM/XA) sessions on a single disc isn't allowed. You could create such a thing, but many CD-ROM drives will have a hard time recognizing it.
See also http://www.roxio.com/en/support/cdr/multisession.html, which goes into more depth.
Discs written with packets are an entirely different story. See section (6-3).
Quick recap: if you want to write some data to a CD-ROM now, and some more later, you write a single data track in multiple sessions (or with packet writing). If you want to write some audio tracks to a CD now, and some more later, you write multiple audio tracks in a single session.
There are eight subcode channels (P,Q,R,S,T,U,V,W). The exact method of encoding is discussed in section (2-43), but it's really only important to note the data is distributed uniformly across the entire CD, and each channel can hold a total of about 4MB.
The P subcode channel identifies the start of a track, but is usually ignored in favor of the Q channel.
The Q subcode channel includes useful information, which can be read and written on many recorders. The user data area contains three types of subcode-Q data: position information, media catalog number (MCN), and ISRC code. Other forms are found in the lead-in, and are used to enable multisession and describe the disc TOC (table of contents).
The position information is used by audio CD players to display the current time, and has track/index information. This can be controlled when doing Disc-At-Once recording.
The ISRC (International Standard Recording Code) is used by the recording industry. It states the country of origin, owner, year of issue, and serial number of tracks, and may be different for each track. It's optional; many CDs don't use this. The media catalog number is similar, but is constant per disc. Note these are different from the UPC codes.
See http://www.ee.washington.edu/conselec/CE/reports/Group.1/matt_page_individual/subcode.html for some details on P and Q.
The R-W subcode channels are used for text and graphics in certain applications, such as CD+G (CD w/graphics, supported by SegaCD among others). A new use has been devised by Philips, called ITTS. It enables properly equipped players to display text and graphics on Red Book audio discs. The most recent result of this technology is "CD-Text", which provides a way to embed disc and track data on a standard audio CD.
Not many publishers use them, and not all devices can read all of the fields.
Programs that identify audio CDs automatically don't rely on an embedded serial number. Instead, they compute an ID based on the quantity and positions of the audio tracks, measured down to 1/75th of a second. http://www.cddb.com/ has a collection of CD information.
It depends on how much data you're going to burn, and how fast your drive is. Burning 650MB of data takes about 74 minutes at 1x, 37 minutes at 2x, and 19 minutes at 4x, but you have to add a minute or two for "finalizing" the disc. Remember that single speed for CD-ROMs is 150KB/sec, double speed is 300KB/sec, and so on.
If you have half the data, it will finish in (about) half the time. If you record the same thing twice as fast, it will finish in (about) half the time.
Most CD recording speeds are linear, i.e. recording at 12x is twice as fast as recording at 6x. If the drive uses a PCAV mechanism (see section (5-22)) the speed varies depending on which part of the disc you're recording. If a "20x" drive uses PCAV to get 12x at the start of the disc and 20x near the outside, you know that burning 60 minutes of audio will take somewhere between about 5 minutes and about 3 minutes.
There are two basic ways of writing to a CD-R. Disc-at-once (DAO) writes the entire CD in one pass, possibly writing multiple tracks. The entire burn must complete without interrupt