Digital recording is a music lover's dream but a music company's nightmare. Since it offers essentially perfect reproduction--on compact discs, digital audiotapes, digital video discs, or even on music sent across the Internet--audiophiles can accumulate vast collections of music, transferring it from one format to another, copying it, and digitally altering it with little effort and no damage to the sound's quality. The same capabilities, however, make it easier for fans to avoid paying royalties to recording companies and artists. Joseph Winograd thinks he's found a way to protect the copyrights of digital music.
Ideally, music companies would like to permanently mark recordings as their own, and perhaps even hide a code in the music that would instruct recording devices not to reproduce it. Pirates could easily isolate and destroy such a code if it's inserted before or after the music, and inserting the code in the body of the recording would blemish the music. "The idea of hiding copyright and other information in music has been looked at for close to two decades," Winograd says, "but the codes were always audible to the listener." Three years ago Winograd, who is vice president of engineering at Aris Technologies in Cambridge, Massachusetts, set out to crack this problem. By analyzing what parts of the digital signal the human ear notices and what it ignores, he came up with a way to encode information by subtly modifying the ignored parts of the signal to generate a mathematically derived pattern. A computer monitoring the digital 0's and 1's of the music can spot the inserted code, but a human listener cannot.
Polygram Records began making cds with Winograd's digital watermarks in February. Royalty collection societies will be the first to electronically monitor songs being played on the radio and bill radio stations accordingly for royalties. The code may also be useful for storing all sorts of hidden information in music signals. Eventually, Winograd says, music companies might encode the name of the artist and song so that the information could pop up on a display on your radio, even though the DJ didn't bother to tell you.
