CD pirates beware鈥攖he music industry has a new weapon up its sleeve.
It鈥檚 called the Cactus Data Shield, and it is designed to add noisy garbage to
all copied CDs. Trouble is, it could also damage the hi-fi and loudspeakers of
people who play pirated CDs.
Sony is already evaluating the Cactus system through its music division,
which has been secretly testing it in Eastern Europe. The system was developed
by Midbar Tech (www.midbartech.com), a company based in Tel Aviv. Midbar Tech
refuses to comment on how its system works, but New 杏吧原创 has dug
out its American patent (US 6208598)鈥攚hich reveals all.
Midbar鈥檚 anti-piracy technology follows on the heels of a similar system from
Macrovision of California, which recently launched its SafeAudio system (New
杏吧原创, 14 July, p 22). This adds uncorrectable errors to the digital
music on a CD, so CD writers on PCs can鈥檛 copy it. But Macrovision admits
SafeAudio doesn鈥檛 work with consumer disc-to-disc CD copiers.
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However, Eyal Shavit of Midbar Tech claims, 鈥淲e can stop all kinds of
copying, even on domestic CD recorders.鈥�
Midbar鈥檚 patent points out that all music CDs store bursts of music code and
control information. The music data is marked with 鈥渇lags鈥� which tell the CD
player to decode it and send it to the amplifier and loudspeakers. The control
information is not decoded. When burning the original CD, Midbar鈥檚 idea is to
replace some of the music with false data and label it as control information.
While CD players do not decode this, they are designed to disguise the gap by
bridging it with guessed data. So the original CD plays acceptably, according to
Midbar.
鈥淭here is little or no net difference in audio quality,鈥� it claims in its
patent, though the company will not identify the 鈥済olden-eared鈥� listeners who
have tested the system.
If the CD is copied, however, the copier machine (a PC or disc-to-disc
copier) sees the fake control data as music. So when the copied disc is played,
there are bursts of distortion as the player tries in vain to decode the
garbage. It not only sounds bad, says Midbar, but it is 鈥減otentially damaging鈥�
to the player鈥檚 circuitry if the added noise has a suitable wave shape.
It is well known in the audio industry that feeding large 鈥渟quare wave鈥�
pulses to sensitive circuitry鈥攑articularly loudspeakers鈥攃an cause
damage because high-frequency harmonics in the steeply rising and trailing edges
cause rapidly repeating high-energy peaks in the speaker output.
Sony has secretly tested Cactus by treating several thousand CDs sold
recently in the Czech Republic and Slovakia, but the system was not set to cause
damage on this occasion. 鈥淲e have had no problems with loudspeakers,鈥� Shavit
says. While acknowledging that it may seem 鈥渦nacceptable鈥� to harm consumers鈥�
equipment deliberately, he adds, 鈥淚t鈥檚 鈥榮weat engineering鈥�. We can add extra
lines of defence as people use new attacks.鈥�
Midbar will not identify the affected CD titles sold in Eastern Europe, so no
independent listening tests are possible.