The ABC's of In-Dash MP3's
Sun Feb 17, 3:08 PM ET
By IVAN BERGER The New York Times
CARS have taken the names of all sorts of places and things, but the Mazda MP3 is probably the first model to be named after a feature of its sound system.
That system (a Kenwood Excelon) plays not only regular compact discs but also discs carrying music in a highly compressed digital format called MP3. A single such disc can hold 10 hours or so of music, more than you'd get from six regular CD's in the optional changer of the Mazda. Not only that, but the system can display the name of each track as it plays.
These are not discs you can buy in your local record store or listen to on most home or car CD players. But you can make your own on any computer that can record (or "burn") blank CD's, and play them on computers, some home equipment and MP3-compatible car players made by most leading makers of car stereos, including Aiwa, Alpine, Audiovox, Blaupunkt, Clarion, Eclipse, Jensen, JVC, Kenwood, Pioneer, Rockford-Fosgate, Sony and Visteon. The players are available as original equipment on a few vehicles, including the Ford Mustang and F-150 pickup.
To get music in the MP3 format, you can copy ("rip") tracks from your own CD's. Free software for doing this is widely available. Or you can download music files from the Internet. Downloading is what made MP3 famous or infamous, from the standpoint of the music industry.
Music converted to MP3 data files can be transmitted relatively quickly over modems. As a result, the Internet has been humming for three years or so with music, most of it free, from a variety of sources.
Some MP3 tracks are deliberately posted to the World Wide Web by little-known artists struggling for exposure, but many more are commercial recordings posted without the permission of those who hold the copyrights. A series of lawsuits has changed the picture, and many free music sources are drying up or, like Napster, are converting to paid subscription services.
The sound quality of MP3 discs doesn't quite match that of regular CD's. But the difference in fidelity can be so small that few listeners will detect it, especially amid the noise in a moving car.
Considering how much data is subtracted from regular CD signals when converting them to MP3, the only reason there is so much music left is that MP3 is a "perceptual coding" system, designed with human hearing in mind.
Perceptual coding works because some musical sounds "mask" others from our hearing, the way the Mazda MP3 would be obscured from view if it were parked behind a bus. Perceptual coders first discard sounds that masking would make inaudible, then make the music even more compact by shaving away the least audible remaining parts, little by little, until the file shrinks to the desired size (a function of the music's length and the number of bits per second in the signal, the "bit rate").
The more that is removed, the smaller the resulting computer file and the lower the sound quality. The bit rates generally considered the best tradeoff between shrinkage and quality are 128 thousand bits per second (kbps), at which the music is compressed to one-eleventh of the size of the same music on a standard CD (or, better, at 160 kbps, which is one-eighth the standard size). If you are picky, you can use higher rates, up to 320 kbps (a mild 4-to-1 data reduction). Lower data rates are also available if storage space and transmission time count more than sonic fidelity.
So far, MP3 is by far the most popular perceptual coder for Internet music transfers, but others now available claim as much as twice the file compression of MP3's with no loss of quality. The best known of these is Microsoft's Windows Media Audio, which can be played by some MP3-compatible Aiwa, Blaupunkt, Kenwood, Pioneer and Visteon car stereos. But another new format claiming this, MP3Pro, can be played on the same equipment used for the original MP3 discs.
If you have downloaded MP3, MP3Pro or Windows Media Audio files, you can play them in your car without buying a whole new stereo. The simplest way is to convert this music to standard CD format before burning new discs from it. (Most CD- burning software provides for this.) That won't bring the sound quality back to true CD levels, but it will make the music available for use on any home or car system that can play home-recorded CD's.
You can also get MP3 players (from Blaupunkt, PhatNoise and others) that hook into your car's stereo system the way a CD changer would. These players store music on portable hard disks that you carry from your car to your computer to reload.
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