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Understanding Digital Formats Part 1: The Digital Revolution and MP3s

[Based on an article by Matt Whitlock on Techlore.com]

The old days: You just stuck in the CD or cassette, and the music played over nearby speakers.

The brave new world: You find yourself downloading, storing, converting, transferring music. Many of us are “ripping” our CD collections into our computerized music libraries. We are buying music online, storing it on our computers, and carrying it around on our mobile Sansa devices (or phones).

Sansa players can use music files in the main widely used formats: MP3s, WAV and WMAs (including WMA Lossless and the secure WMA audio files used in many online store purchases).

So we have some questions to answer:

  • What format are we going to store our music in?
  • And, do we lose anything if we buy a music player that doesn’t use the less common formats?

Here are some basics that may help you understand digital music formats, and make the decisions you need to make.

  • Here, in Part 1, we’ll discuss some basics of digital formats and compression, and look at the main format used today: MP3s.
  • In Part 2, we will look at the other digital format used by Sansa players, Microsoft’s WMA and we will briefly look at other formats that Sansa players can not play.
  • And in Part 3, I will offer basic advice on which format to use.

A Little History of the Portable Music Explosion

Music used to be stored on vinyl records or cassette tape recordings that stored the sounds in analog format (meaning that the music is conveyed using continuous electric waves that mimic and reproduce the continuous sound waves we use to hear.) These formats meant that our music was stored in ways that were often fragile. (Records could scratch, tapes could fade!) And making the music required mechanical devices for sound production (remember the record needle?)

First the cassette revolutionized music listening by making everything portable. You couldn’t listen to a record walking down the street, but you could listen to an audio cassette on your new Walkman, and you could record your own music mixes, share them, and listen to them on earphones.

Then came Compact Discs (CDs) in the 1980s, which brought digitally encoded sound center stage. With digital recording, the sound is recorded in small bits (0s and 1s). If there enough bits per second, then they accurately reproduce the continuous tone of sounds. And the advantage of digital recording is that the sounds are now recorded in a way that can be stored and played in ways that are radically more stable and portable.

A CD holds music in the Pulse Code Modulation (PCM) format. This is a common method for digitizing analog signals. PCM signals are uncompressed. The resulting digital stream (and recordings) take up a great deal of space.

CD players stream music data off the CD disc at a rate of 1.41 million bits per second. This means that 30 minutes of audio will take up approximately 318 Megabytes of space. This is ok when you are storing the music on a CD (which has a huge capacity). But it is simply too large to efficiently store music on your computer, load it on your portable music player or download it over the Internet.

So, for the computer world, new music formats need to compress the music files – by cleverly taking out unnecessary data without destroying the final music quality. Throughout the 80's and much of the 90's, there was no great way to accomplish this task at home. Then it happened.

Now we are in a second major leap as new ways are being developed for compressing the digital recordings – so that it takes less space to store and less time to download.

MP3 Format

The arrival of the MP3 format shook the music world, and intersected with the explosion of the modern Internet. Suddenly music could be bought (and swapped!) online. New ways of selling, storing, sharing and pirating music started taking over. And we could suddenly carry and play our music in smaller and smaller devices that didn’t need to play jumpy CDs or fragile cassette tapes.

The name MP3 is an abbreviation for International Standards Organization - Motion Picture Expert Group Audio Layer 3 (ISO-MPEG Audio Layer 3). MP3 is now the extension used at the end of the music file name – for example: “songname.mp3”.

The heart of this story: MP3 is a very powerful compression codec (encode-decode system). MP3 revolutionized the way audio files were encoded, making it possible to store them in remarkably small files.

The sizes of the files vary depending on the “bit rate” you chose to encode them. A smaller bit rate produces a smaller file, but it also produces less quality of sound. The range of bit rate is from 32 to 360 kbps. The smaller bitrates are find for voice recordings (speeches, interviews, lectures, dictation etc.) And the most popular bit rates for music are between 128 to 192 kbps.

Most people now record, store, share and play their music in the MP3 format. It is so widely used that it has become the "standard." Nearly all software players and portables (including, of course, all the Sansa products) are designed to download, store and play this format.

However the same tricks that MP3 uses to make tiny files also create some problems and controversies. Specifically, MP3 is a “lossy codec” – meaning that it identifies data in the original recording that it considers “unneeded” and throws it away. However, this also means that MP3 files do not sound quite as crisp or accurate as the original CD recordings. Most of us (apparently) don’t notice or care about that difference – either because it is too small to notice, or because the size benefits of MP3 are irresistible.

Inevitably, other newer formats have emerged – some of which can make files that produce the same quality as mp3s but in slightly smaller files.

We will discuss them in Part 2.

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