ANTI-PIRACY compact discs that cannot be copied by a computer have gone on
sale in California. The first CD title has already sold 100,000 copies, but it
is causing concern among audio experts because they fear that the music may be
audibly distorted.
The SafeAudio system was developed by Macrovision, a California-based company
best known for its anti-piracy video systems. The technology stops people
“ripping” music CDs to create high-quality digital copies on a computer hard
disc or for downloading to a portable player. The system also prevents people
creating digital files from the CD to swap over the Internet or copying music
onto a blank CD—although it would still be possible to make a poor quality
copy by converting the analogue output into digital code.
SafeAudio works by degrading the digital code. The CD will still play on an
ordinary player or through a computer’s speakers or headphones. But it cannot be
copied. Macrovision says that the changes made to the music are not
discernible.
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Macrovision is reluctant to discuss how SafeAudio works, but has told New
Scientist that it is based on work done by TTR Technologies of Israel.
Patents filed by TTR describe how a “copy-protected audio compact disc”
works.
The patents say the system deliberately gives some of the digital code on the
CD “grossly erroneous values”, adding bursts of hiss to the audio signal. In
addition, the error-correction codes on the CD, which would normally correct
such errors, are distorted. So error correction fails, leaving tiny gaps in the
music.
When this happens, a consumer CD player bridges the gaps. It looks at the
music on either side of the gap and interpolates a replacement section. A
computer does the same when playing CDs for listening.
But the computer’s CD drive cannot repair the digital data going to the hard
disc. So the hard disc copies nothing, or a nasty noise. TTR says the repairs
made by a music CD player are not audible. Macrovision has improved the TTR
system, says David Simmons, managing director of Macrovision’s British
subsidiary.
The company says it has spent six months playing discs to consumers, and to
professional listeners—known as “golden ears”—at two major record
companies. None detected any distortion. An as yet unidentified album with
SafeAudio copy protection has also gone on sale in California. “There was no
increase in return rate or complaints,” says Macrovision’s Heinz
Griesshaber.
But this doesn’t placate hi-fi buffs. “It’s a dreadful, dreadful thing to
contaminate the sound deliberately, says Martin Colloms, a British hi-fi expert
whose columns are syndicated around the world. “We all hate piracy but the idea
of mucking up the sound of a recording is reprehensible. It’s like slashing
paintings in a gallery to stop someone stealing them.”
