How It Works: Hardware MP3 Players

Michael Gowan, special to PCWorld.com

Hardware MP3 player: a device that stores, decodes, and plays digital audio files without requiring a PC.

The digital music revolution has freed your favorite songs from the tyranny of a physical form. Virtually identical digital copies, in formats such as MP3 or WMA, allow you to listen to the same song over and over without fear of wearing out a cassette or scratching a CD.

But the idea of digital music isn't nearly as interesting if you can listen to it only on your computer. That's the beauty of MP3: Not only can you transfer these small files but you can store them easily on inexpensive portable playback devices. All you need is a player to transfer your music files to. You can now find a ton of portable players and components for your stereo that set the music free from your PC.

Here are the vital statistics:

• Many hardware MP3 players use a digital signal processor (or DSP) to handle the tasks of transferring and decoding MP3 files.
• In addition to the traditional portable players, manufacturers now produce MP3-capable stereo components, car stereos, and even digital cameras and mobile phones that can play MP3 files.
• You can expect the next generation of players to store more music, have faster processors, and support more music file formats.

A hardware MP3 player is a stripped-down, application-specific computing device, with enough power and the specific components needed to store, organize, and play digital music files, as well as display information about them. The player itself behaves as an application would, managing the digital music files you've created and downloaded to the player beforehand.

The heart of any MP3 playback device is its digital signal processor. The DSP handles data transfers, controls the device's interface, and decodes the file for playback. The DSP does just a few things but does them quickly, and uses little power in the process (an especially beneficial trait for portable players).

The process begins when you create or download a digital music file using your PC. When you create a file in the MP3 format (or in the competing WMA and AAC formats), the software that creates the file tosses out bits of data to make the file smaller, a process called lossy compression. (For more on this process, see our companion article, "How It Works: MP3.")

Size Is Everything

The main limitation of most hardware MP3 players is the amount of onboard storage space for holding digital music files. You can create smaller MP3 files by compressing them more. You can tell how much information has been thrown out by looking at the compression level, expressed as the number of kilobits of data that represent 1 second of music. The lower this number, the greater the compression. However, the playback quality suffers below a subjective threshold that varies from person to person but averages about 128 kbps. A song MP3-encoded at 160 kbps will sound much better than the same song MP3-encoded at 96 kbps, but the 160-kbps song will take up nearly twice the space, leaving less room for additional songs.

Once you have a file, you must transfer it to the device's memory. If the device uses only built-in memory, you will have to connect the player to a PC's USB, serial, or parallel port connection, which sends the data from the PC's hard drive to the unit's memory. If the device uses a removable storage medium, you may be able to copy the files directly to the storage medium more quickly than you can via the USB port. Some stereo-component MP3 players also have a built-in encoder that can read and compress digital music files directly from a CD and store it on the unit's memory, without requiring a PC.

The first generation of players used nonvolatile flash memory--a type of data storage that is similar to your computer's RAM but doesn't lose its contents when you cut off the power--to store the digital audio data. Newer players offer more choices, including internal hard drives or removable storage such as Iomega's PocketZip or IBM's Microdrive.

After you select which song you want to hear (using the player's built-in controls and, often, an LCD screen that gives song, artist, and track time information) from the files in the player's memory, the data moves to the DSP, which decompresses the file. The decompression software can be embedded on the processor or in the unit's memory. Next, the DSP passes the song data to a digital-to-analog decoder, which converts it from binary digital information into the analog audio signal that controls how your headphones or speakers create the music. Some players also have small preamplifier circuits that boost the strength of the audio signal as it emerges from the decoder, before it reaches the headphone jack.

MP3 Everywhere

It seems as if every company that makes home audio equipment (not to mention a host of computer peripheral vendors) makes or sells at least one MP3 player these days. You'll find portable players that let you take the music with you, components that bring MP3 files to your stereo, and even hard-drive-based units that replace your car stereo.

Thanks in part to the music file-sharing phenomenon Napster, digital music has become more mainstream, and MP3 hardware sales reflect that. Ric Dube, an analyst with Webnoize, a digital-entertainment research firm, estimates that sales of portable players increased about 150 percent from the beginning until the end of 2000.

The first widely available player came from the company then known as Diamond and now known as SonicBlue. Its portable player, the Rio, tested the market (and the limits of the law, after the Recording Industry Association of America sued the company to prevent the player's sale). Though the music industry argued that the mere existence of MP3 players encouraged music piracy, it failed to prove its case, and the floodgates opened. Now consumers can choose from a wide variety of units--in all shapes, sizes, and memory capacities--from traditional consumer audio companies such as Sony and RCA, as well as PC hardware makers such as Intel and Creative Labs.

Consider Storage, Then Price

Portable players are the most common, and most affordable, hardware MP3 player option. You'll find a wide variety of products, but the most important factor to consider when you're contemplating a purchase is storage: How much does the player have, and what kind does it use? More storage obviously equates to longer play times; assume you'll get about 1 minute of music per 1 megabyte of storage.

On the low end, SonicBlue's Rio players and D-Link's DMP-CD100 ship with 32MB of onboard flash memory and cost less than $200. SonicBlue, Creative, and others also make portables with 64MB of flash memory that cost between $200 and $300. If you want to add more memory, you must buy fairly expensive flash memory cards, which can run you $100 for 32MB. Sony products such as the $300 pen-size Vaio Music Clip use Sony's less-expensive Memory Stick for storage.

Iomega and Sensory Science make players that use Iomega's PocketZip (formerly known as Clik) removable media, which costs $10 for 40MB. For those who want serious storage, Creative's $500 Nomad JukeBox and Archos's $350 Jukebox 6000 MP offer a far cheaper option: They store music files on internal 6GB laptop hard drives--enough space to hold hundreds of hours of music.

Take Your Home and Car Stereos Digital

For your existing home stereo system, you can get players with a lot of memory and music management options. Players from Request Multimedia and Sima have hard disk storage options at 10GB, 20GB, and even 40GB capacities, as well as built-in CD players that also encode the MP3 files without requiring a PC, with prices that start at about $800. Many of these players also include ethernet networking ports so that you can download music off the Internet using the PC and easily move the files to the component; some also allow you to connect the device to a TV set so you can use an on-screen interface to better manage hundreds of files.

But you don't play music just on a portable or on your stereo; you probably also want to listen to music wherever you are, whatever you're doing. For your car, MTE's Neo and Aiwa's CDC-MP3 are in-dash, hard-drive-based players. More car players are on the way from traditional car stereo companies and the big names in the MP3 market such as SonicBlue. You download your music collection from your PC onto the player's hard disk through a USB connection and then keep the unit in the car until you build up enough new MP3s to make it worth the hassle to lug it back into the house to download more.

Your personal digital assistant can also become a portable music player, with InnoGear's $259 MiniJam MP3 Player for the Handspring and PocketPyro's $299 Pyro for the Palm. You can even get mobile phones and digital cameras that have MP3 capabilities built in.

Webnoize's Dube says that in the coming years you can expect to see MP3 players built into almost any device you can link to a PC. Of course, most of these will fail, but that doesn't mean the manufacurers won't try. Also expect to see more (and cheaper) storage, faster processors, and more features, including portable players that can encode as well as decode.

Michael Gowan is a freelance technology author based in the San Francisco Bay Area.