Re: [linux-audio-user] Reading/playing a "copy protected" CD : Reed-Solomon correction?

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To: A list for linux audio users <linux-audio-user@...>
Date: Monday, June 28, 2004 - 7:56 am

Almost a year ago, I wrote a message to the list on how I managed
to play a Cactus Data Shield copy protected (mutilated) 'CD' with
linux. See below. The link to the original thread:


A collegue of mine just bought the new Radio Head CD, Hail To The Thief.
As the box says, this CD is "Copy Controlled". Some searching on the web
revealed that it's using so called Cactus Data Shield 200 protection, which
means deliberate errors on the cd, that most (not all!) CD players deal
with correctly, but cd-rom readers don't. So, what if you want to play
your "CD" on a computer? Well, the CD also includes a data track, with a
MS Windows (yeah..) application. However! This application does not play
the CD audio but a compressed format also included on the CD! Another
interesting issue is that the fake errors might actually cause problems
when some real errors occur on the CD, that normally would have been
corrected, but not anymore in combination with the fake errors.

Obviously, all this is completely unacceptable, so I advice you to never
buy a Copy Controlled CD. If you have bought one, bring it back to the
store. They have absolutely no reason not to give you your money back.

(From the web: 'Philips controls the CD standard and their spokesman
says: "Any changes that put a disc outside the CD standard result in a
disc that should no longer be described or marketed as a CD." Philips,
because of conformity issues, has warned the record labels that the
discs are actually not compact discs at all, and must bear warning
labels to inform consumers.'). I'd add that stores should then not be
allowed to sell these CD's in a part of the store that says "Compact

Note that I did manage to play the CD with Linux. My very old (>6 years)
SCSI cd writer has been able to read the copy protected CD with
cdparanoia. but... in the left channel, every 5.8 sec some values are
distorted: about 10 groups of 1 to 3 samples in a row get an extreme
value (not always the same, but near maximum). I wrote a small
application that corrects those distorted values (linear interpolation
with the surrounding samples). I assume this information is legal,
because it is only to play the cd, not to copy it.


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Messages in current thread:
[linux-audio-user] Reading/playing a "copy protected" CD : R..., Mikhail Ramendik, (Sun Jun 27, 11:13 am)
Re: [linux-audio-user] Reading/playing a "copy protected" CD..., Maarten de Boer, (Mon Jun 28, 7:56 am)
Re: [linux-audio-user] Reading/playing a "copy protected" CD..., Erik de Castro Lopo, (Fri Jul 2, 9:34 am)
Re: [linux-audio-user] Reading/playing a "copy protected" CD..., Sampo Savolainen, (Sun Jun 27, 12:50 pm)
Re: [linux-audio-user] Reading/playing a "copy protected" CD..., Mikhail Ramendik, (Sun Jun 27, 11:24 pm)
Re: [linux-audio-user] Reading/playing a "copy protected" CD..., Malcolm Baldridge, (Mon Jun 28, 1:22 am)
Re: [linux-audio-user] Reading/playing a "copy protected" CD..., Mikhail Ramendik, (Sun Jun 27, 11:21 pm)
[linux-audio-user] The copy-protected (or broken?) recording, Mikhail Ramendik, (Fri Jul 2, 1:49 am)