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How MP3 Players Work


The MP3 player is the most recent in an evolution of music formats that have helped consumers enjoy their tunes. Records, 8-track tapes, cassette tapes and CDs -- none of these earlier music formats provide the convenience and control that MP3 players deliver. With an MP3 player in hand or pocket, a consumer can create personalized music lists and carry thousands of songs wherever

they go.

All of that stored music and the MP3 player itself fit into a device that, in some cases, weighs less than one ounce. Portability is a large factor in the popularity of the MP3, considering the ease of transportation in comparison to a CD player and CD storage case. In addition, some devices provide additional technology, like video and photo viewing, alarm and calendar functions, and even cell phone and Internet service.­

­In this article, you'll learn more about the technology inside MP3 players and the diff­erent types of players available. You'll also find out how to get tunes and how you can accessorize your player. Get started by learning about the MP3 file format on the next page.

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The MP3 File Format

The MP3 file format revolutionized music distribution in the late 1990s, when file-swapping services and the first portable MP3 players made their debut. MP3, or MPEG Audio Layer III, is one method for compressing audio files. MPEG is the acronym for Moving Picture Experts Group, a group that has developed compression systems for video data, including that for DVD movies, HDTV broadcasts and digital satellite systems.

Using the MP3 compression system reduces the number of bytes in a song, while retaining sound that is near CD-quality. Anytime you compress a song, you will lose some of its quality, which is the trade-off for the ability to carry more music files in a smaller storage system. A smaller file size also allows the song to be downloaded from the Internet faster.

Consider that an average song is about four minutes long. On a CD, that song uses about 40 megabytes (MB), but uses only 4 MB if compressed through the MP3 format. On average, 64 MB of storage space equals an hour of music. A music listener who has an MP3 player with 1 GB (approximately 1,000 MB) of storage space can carry about 240 songs or the equivalent of about 20 CDs. Songs stored on traditional CDs are already decompressed, so it takes more CDs to store the same amount of songs. (Some CDs support MP3 files.)

Although MP3 is perhaps the most well-known file format, there are other file formats that can be played on MP3 players. While most MP3 players can support multiple formats, not all players support the same formats. Here are a few of the file formats that can be played on different players:

  • WMA - Windows Media Audio
  • WAV - Waveform Audio
  • MIDI - Music Instrument Digital Interface.
  • AAC - Advanced Audio Coding
  • Ogg Vorbis - A free, open and un-patented music format
  • ADPCM - Adaptive Differential Pulse Code Modulation
  • ASF - Advanced Streaming Format
  • VQF - Vector Quantization Format
  • ATRAC - Sony's Adaptive Transform Acoustic Coding 3

In the next section, we'll look at the technology behind the player that allows you to listen to your music.

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The Technology

Unlike earlier forms of music players that required moving parts to read encoded data on a tape or CD, MP3 players use solid-state memory. An MP3 player is no more than a data-storage device with an embedded software application that allows users to transfer MP3 files to the player. MP3 players also include utilities for copying music from the radio, CDs, radio or Web sites and the ability to organize and create custom lists of songs in the order you want to hear them. This list of songs is called a playlist.

The MP3 player is the convergence of many technologies. Alone, none of its components are revolutionary, but together they create an unprecedented consumer product.

Specific components may vary, but here are the basic parts of a typical MP3 player:

  • Data port
  • Memory
  • Microprocessor
  • Digital signal processor (DSP)
  • Display
  • Playback controls
  • Audio port
  • Amplifier
  • Power supply
 
 

The player plugs into your computer's USB port, FireWire port or parallel port to transfer data. USB-based players transfer data many times faster than those that use the parallel port. The MP3 files are saved in the player's memory.

Memory types include:

With the exception of the last one, these are all types of solid-state memory. The advantage to solid-state memory is that there are no moving parts, which means better reliability and no skips in the music. MP3 players that contain tiny hard disk drives can store 10 to 150 times more than Flash memory devices can.

The microprocessor is the brains of the player. It monitors user input through the playback controls, displays information about the current song on the LCD panel and sends directions to the DSP chip that tells it exactly how to process the audio.

 
 

In addition to storing music, the MP3 player must play music and allow the user to hear the songs played. To do this, the player:

  • Pulls the song from its memory.
  • Decompresses the MP3 encoding, through DPS, via an algorithm or formula.
  • Runs the decompressed bytes through a digital-to-analog converter into sound waves.
  • Amplifies the analog signal, allowing the song to be heard.

All of the portable MP3 players are battery-powered. Most use a rechargeable internal lithium battery and last for approximately 10 to 28 hours on a single charge. Many of the players also have AC adapters so they can be plugged into a normal electrical outlet, and some even offer DC adapters for use in a car.

In the next section, we'll learn about the different types of MP3 players.

Types of MP3 Players

The Apple iPhone has a 4 GB or 8 GB flash drive.
The Apple iPhone has a 4 GB or 8 GB flash drive.

MP3 players are as varied as the people who buy them. Choice is based on several factors, including how you plan to use it, the amount of music you want to carry in your MP3 player and how much you are prepared to pay. Let's take a look at the four basic types of MP3 players.

Flash Memory Players

The flash memory MP3 player is the smallest and lightest and typically stores fewer songs than hard drive players. Because it's small and contains no moving parts, it's ideal for exercisers. And with some models boasting up to 8 GB of storage (2,000 songs) and other models offering video and photo capability, it also appeals to the multimedia aficionado. Its batteries can last up to 28 hours.

Hard Drive and Mini-hard Drive Players

Hard drive players are larger and heavier than flash memory players and offer considerably more storage. (The Apple iPod holds up to 80GB.)

For those looking for a player that can contain their entire music collection (up to 20,000 songs), photographs, data, and video and allow podcast recording, the hard drive is best. However, these features and the hard drive consume more power, with some batteries lasting eight to 20 hours for music playback and up to six hours for video playback. The players include moving parts, which may skip. However, some players have anti-shock buffers and or anti-skip protection.

Smaller in size and internal storage capacity, miniature-hard drive players are lighter than traditional hard drive players, but contain less memory -- usually up to 8 GB. They, too, contain moving parts.

MP3 CD Players and MiniDisc MP3 Players

There is a breed of CD players available that plays MP3 and other digital files. These MP3 files are burned to CD-R/RW discs from your old CD collection and used in the MP3 CD player. A CD can hold about 10 hours of music. A CD burner is necessary for those buying an MP3 CD player. The MP3 CD player is cheaper than the flash memory and hard drive memory players, but may skip when jostled. They are also much larger in size than their digital counterparts.

Myvu video goggles connect to an iPod and project sound and “floating video images.”
Myvu video goggles connect to an iPod and project sound and “floating video images.”
Photo courtesy Damien Dovarganes/ Associated Press

­For those who appreciate MiniDisc technology, there's Sony's MiniDisc Walkman digital music player. This player supports the trademark Sony file format codec ATRAC3 -- but it also supports MP3, WMA and WAV formats, too. And the multitasking doesn't stop there. Sony reports that the 1GB Hi-MD discs can also store and transfer loads of PC data files (think PowerPoint presentations, spreadsheets, et cetera). The discs retail for less than $10, store up to 600 songs and are re-recordable. Depending on the model, users can expect anywhere from 30-plus hours of playtime from just one AA battery.

The Hybrid Players

MP3 is no longer just a stand-alone technology. Technology companies are now offering MP3 capability in other consumer products, including satellite radios, personal digital assistants, DVD players, sunglasses, swim goggles and even a combination Swiss Army Knife-MP3 player. Most notably, the iPhone from Apple crosses a cell phone with an iPod and Web browser, along with a variety of other features.

Filling Up Your Playlist

iTunes allows users to download music, audio books, television shows, movies, roadio broadcasts and podcasts.
iTunes allows users to download music, audio books, television shows, movies, roadio broadcasts and podcasts.
Photo courtesy Apple

With MP3 players, consumers become their own disc jockey, picking the songs they want to hear when they want to hear them.

Potentially hundreds or thousands of songs are at the listener's fingertips. Songs can be ordered into a playlist by genre, artist or mixed into random order. The first step to creating a playlist is finding songs. That's not a problem -- there are many sources for MP3 files.

Ripping

If you have a collection of CDs and want to convert those CDs to MP3 files, you can use ripper and encoder software. Some MP3 players come with such software. A ripper copies a song's file from the CD onto your hard disk. The encoder then compresses the song into the MP3 format, allowing it to be downloaded to your MP3 player.

The basic process for ripping is as follows, although steps will vary based on individual software programs:

  1. Place the CD into the CD drive of your computer.
  2. Select the track for the song you want to convert to MP3 format.
  3. Convert the track.
  4. Copy the new MP3 file to your hard disk.
  5. Download the MP3 file to your MP3 player.

For Free and For Fee

There are many online music sites, like iTunes, that offer songs for purchase, with some providing songs free of charge as a way to introduce an unknown artist.

Yet another option is subscription-based plans like Rhapsody. These services provide all the songs you want at one flat fee. However, there are two types of MP3 files that affect the subscription or song purchase: copy-protected and unprotected. The first ensures that the songs cannot be file-shared. If your subscription lapses, you can no longer play the songs. Music is also encoded with digital rights management technology -- anti-copying software -- to enforce the subscription agreement or limit the amount of times the song can be burned. The second, unprotected files -- offered on sites like eMusic -- is unrestricted, and once downloaded, can be used indefinitely.

Other Audio Sources

Many MP3 players have the ability to record songs directly from your CD player. For those who don't want to bother with a computer, this streamlines the conversion process. No longer do users put a CD into the computer, rip the track from it, convert it to MP3 format, save it and then download it to an MP3 player. The song goes directly from the CD to MP3 format in the user's preferred playlist.

Some MP3 players also have a built-in FM radio tuner, providing users with an additional source of entertainment. Radio listeners can record the tunes from their favorite stations in the MP3 format and instantly add it to their playlist. Several MP3 players allow you to playback your MP3 music on your FM radio using unused frequencies.

Some combination cell phone-MP3 players allow the user to browse and purchase songs, which are then delivered to the phone for immediate playback.

An additional audio source is the user's own voice, which can be recorded on an MP3 player and then transferred to a computer for storage or transmission via e-mail.

In the next section, we'll look at the many accessory options for your MP3 player.

Accessorizing Your MP3 Player

Apple iPods dominate the MP3 player market, resulting in myriad accessories.
Apple iPods dominate the MP3 player market, resulting in myriad accessories.
Photo courtesy Paul Sakuma/Associated Press

As with any popular consumer product, there is an entire industry devoted to selling MP3 player accessories. Users looking to personalize their digital music players can find myriad options to fit any lifestyle.

MP3 enthusiasts can choose from a variety of bags, belt clips and armbands to carry their music with them. These users may also have a need for battery packs to extend playback time. Battery packs can extend playtime up to 10 hours.

For music fans using their computers at home or at the office, the Radio Shark allows a user to record directly from their favorite AM or FM radio program, with the ability to schedule a recording. Additionally, the user can pause a show and return to it at that exact point hours later, just as a digital video recorder can be used to record and pause TV shows. The device works with any Mac or PC computer.

For iPod users looking to expand their video-watching options, there's Myvu Video Goggles. According the company, the lightweight goggles provide a "hands-free, big-screen viewing experience" by connecting to the iPod and projecting sound and "floating video images." The back-pack battery can be used for up to eight hours of viewing.

Docking stations can transform some portable players into a stereo system. A docking station or base includes speakers, and once the player is added, the volume can be controlled through the base. Some include a battery charger. In some cases, MP3 players and docking stations are replacing stereo components in home entertainment systems. There's even a George Forman grill that incorporates a docking station and allows the chef to listen to tunes while grilling.

In addition, the Instant Music Audio Capture device converts old analog records and cassettes into digital files that you can burn on your MP3 player.

And for those in transit, an FM transmitter uses FM radio frequency to broadcast MP3 player music through the car stereo, using either batteries or the cigarette lighter as a power source.

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