CHEAT SHEET
How's this for a technological breakthrough? The music industry's latest gambit to keep you from copying CDs is making it impossible to play them in the wrong places. Trouble is, it isn't perfect. In December, the Universal Music Group began releasing "copyproof" discs that come with warning labels telling buyers to watch out for playback problems - as in, don't be surprised if the CD won't work in your stereo system, computer, game console, or car.
So just how does this stuff work? The companies marketing copyproofing aren't telling, but according to Chris "Monty" Montgomery, the lead programmer of open source MP3 rival Ogg Vorbis and the author of CD ripper cdparanoia, they employ one or both of two basic technologies.
Method 1: Include Errors
The data on a CD is stored in thousands of microscopic "pits." Because the information that makes up the analog signal to the amplifier is encoded with redundancies, a standard CD player can decipher the signal, even if it encounters a lot of errors (e.g., a scratch). CD-ROM drives are often stymied by these errors, so record makers lace CDs with corrupted data to keep music listeners from playing copyrighted discs in a CD-ROM drive, where they might be tempted to copy songs. "It's the data equivalent of rubbing a CD with 120-grain sandpaper," says Montgomery. "But a good CD-ROM drive will correct for the same amount of error that a CD player will, and a crappy Best Buy Walkman will trip up."
Method 2: Disguise Music as Data
CDs contain a table of contents that tells standard players and CD-ROM drives where each track starts and ends. It's the first thing any player looks for when you press Play. Files come in two varieties - music and data. Some copyproof CDs now mask audio files as data files. As a result, many ripping programs can't find any audio tracks on protected discs, so they can't copy them. There are two hitches, however. Programmers will quickly update their software to look past this. And some regular CD players won't play these discs; masked files can trigger a built-in safety mechanism that keeps them from reading data files because the noise could damage your speakers.
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