www.newscientist.com/news/newsŠ

The World's No.1 Science & Technology News Service* *
Anti-piracy CD system raises distortion fear
16:03*16*July*01

*"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."

* 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.


Bursts of hiss

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,


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John I-22
(that's 'I' for Initial...)
Recognising what's NOT worth your time, THAT'S the key.
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