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How Do MP3 Players Work Explained in Plain English

How do MP3 players work? Would you believe magic? Not really of course, but it almost seems that way when you compare them with the previous 110 years of audio recording technology.

A Brief History of Recorded Music

Recorded music - or any audio recording for that matter - became possible in 1877 when Thomas Edison invented the phonograph. Edison recorded Mary had a little lamb on a hand-cranked machine with a tinfoil cylinder and a megaphone-like "speaker" (remember the old RCA logo?). For 50 years cylinders and disks of metal, wax and other materials were the primary recording media.

Vinyl records hit the scene in 1929 and dominated the next 40 years. Magnetic recording tape was developed in the late 1920s but didn't gain widespread popularity until the 1960s (remember the ill-fated 8-tracks?). In 1985 Sony and Philips developed the Compact Disc standard. Three years later CD sales surpassed vinyl records, and eventually tapes, as the media of choice.

In 1987 Fraunhofer IIS created the MP3 encoding algorithm, making today's digital audio players possible. The portable MP3 player made its debut in the spring of 1998 when Saehan-Eiger Labs of Korea introduced the MPMan. Diamond Multimedia's Rio PMP300 was introduced a few months later with greater success, leading many to mistakenly believe it was the first.

Mechanical and Analog vs. Electronic and Digital

Unlike the mechanical functions of records, tapes, and CDs, digital music players have few or no moving parts. Records and tapes store an analog sound signal while CDs are digital. But play-back is similar in that each must interface with and move past a sensing device to read the signal - stylus (needle) for records, magnetic head for tapes, and laser for CDs. The signal is then amplified and sent to the speakers or headphones.

Sounds we hear are air pressure waves, that when recorded are called analog audio. The closer the wave's peaks and valleys, the higher pitched the sound (higher frequency). Lower frequencies like deep bass are widely spaced waves. A good example is a speeding race car. As the car approaches you the waves are compressed, creating a high-pitched whine. As it moves away the waves spread out and the pitch lowers to a roar.

Because a digital file is a series of ones and zeros it can't duplicate the constantly curving analog wave, so a technique called sampling is used. Samples, or bits, are taken thousands of times per second. The rate of this sampling is the bitrate, expressed as Kbps. Graphically bits appear as stair steps going up and down the wave. The higher the bitrate, the smaller and closer the steps and the more closely they resemble the wave.

A Short Lesson on Codecs

Converting music to a digital file closely resembling its analog waveform can require more than a million bits of data for each second of sound. Without getting too technical you can see this will consume a lot of memory in a hurry. Think about it - even a standard CD only holds about 80 minutes of music. The solution is file compression, which can be lossless or lossy. Lossless encoding like FLAC, on average, will compress a music file about 35%, so you still have very large files.

But here's the good news. The human ear can only discern sounds from about 20 Hz to 20 KHz, a relatively small portion of the sound spectrum. Lossy compression algorithms discard all sounds outside this range and certain frequencies within it in a way that tricks the ear into thinking they are still there. Lossy compression is known as "destructive" because discarded sounds are permanently lost, but near-CD quality sound can be retained with compression rates of 90% or more.

Hooray! Now we can store more than just a few songs without using up our entire computer or player's memory. These algorithms are called codecs, which stands for the compression/decompression function they perform. MP3, WMA, AAC, OGG and ATRAC are some of the more common lossy codecs.

Putting It All Together...

The codec software coverts analog music to a small digital file which is stored in the MP3 player's memory. Depending on the bitrate, flash memory players will hold up to 250 songs and hard drive players several thousand. The codec is embedded in the song's file so the player must support it. For example if it's an AAC file and your player only supports MP3 and WMA, it won't work.

But assuming everything matches, here's what happens when you listen to your songs. Software embedded in the player reads the file, decompresses it, converts it back to analog (remember you can't hear digital), amplifies the signal and sends it to the headphones. And voilà, we have crystal clear sound without the annoying cracks, pops and hisses common to records and tapes.

Choices, Choices, Choices...

Even with a seemingly never-ending stream of new products, there are really only three types of personal MP3 players to choose from.

1. Flash Players - the smallest, least expensive, and most reliable. Solid state memory means they have no moving parts, so batteries last longer and skips are eliminated. Capacities range from about 128MB to 4GB and will increase to 16GB in the next couple of years. The newest models support photos and video as well as music, and aren't much larger than a credit card.

2. Hard Drive Players - tiny hard drive memories in these mp3 players are up to 80GB or more and hold thousands of tunes. Some also support photos and video. Anti-skip technology helps, but shock or vibration can still cause skips. They typically have more features than most flash players, and are roughly the size of a deck of cards.

3. CD MP3 Players - the latest generation of portable CD players employ MP3, WMA and ATRAC formats to play (some also burn) CD's that hold 10 to 45 hours of music per disc on standard and/or 3" MiniDisc CDs. Standard CD-sized models are very inexpensive. MiniDisc models cost more but hold the most music per disc and aren't much larger than a hard drive player.

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