[linux-audio-user] Reading/playing a "copy protected" CD : Reed-Solomon correction?
mr at ramendik.ru
Thu Jul 1 20:19:01 EDT 2004
Maarten de Boer wrote:
> 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:
Question: what did the copy-protected CD sound like when played on
CD-ROM? I'm just starting to think that what I have is after all a
problematic recording, not copy protection. At least, no data track
seems to be there (at least Linux does not mount it).
Yours, Mikhail Ramendik
> 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.
More information about the Linux-audio-user