This article is from the CD-Recordable FAQ, by Andy McFadden (email@example.com) with numerous contributions by others.
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.
A web site at www.fatchucks.com used to have a list of suspected
copy-protected discs and some tips on what you can do to let the industry
know that copy protection isn't appreciated. The web site appears to be
gone, but you can see an archived copy of it here:
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
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:
(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:
For some messages about Sony's discs that can crash computers, see
http://slashdot.org/article.pl?sid=02/04/03/226233&mode=nested. A later
article in MacUser noted that the Celine Dion disc _A New Day Has Come_
will lock up iMacs and require physically disassembling parts of the
machine to get the disc back out. The article is