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 鈥渞ipping鈥� 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 鈥� although it would still be possible to make a poor quality copy by converting the analogue output into digital code.
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SafeAudio works by degrading the digital code. The CD will still play on an ordinary player or through a computer鈥檚 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 杏吧原创 that it is based on work done by TTR Technologies of Israel. Patents filed by TTR describe how a 鈥渃opy-protected audio compact disc鈥� works.
The patents say the system deliberately gives some of the digital code on the CD 鈥済rossly erroneous values鈥�, 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鈥檚 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鈥檚 British subsidiary.
Golden ears
The company says it has spent six months playing discs to consumers, and to professional listeners 鈥� known as 鈥済olden ears鈥� 鈥� 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. 鈥淭here was no increase in return rate or complaints,鈥� says Macrovision鈥檚 Heinz Griesshaber.
But this doesn鈥檛 placate hi-fi buffs. 鈥淚t鈥檚 a dreadful, dreadful thing to contaminate the sound deliberately, says Martin Colloms, a British hi-fi expert whose columns are syndicated around the world. 鈥淲e all hate piracy but the idea of mucking up the sound of a recording is reprehensible. It鈥檚 like slashing paintings in a gallery to stop someone stealing them.鈥�
