How do mp3 files work.

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How do mp3 files work

The MP3 movement started not with the industry itself but with a huge audience of music lovers on the . The MP3 format for digital music has had, and will continue to have, a huge impact on how people collect, listen to and distribute music.

The MP3 Format
If you have read
, then you know something about how CDs store music. A CD stores a song as digital information. The data on a CD uses an uncompressed, high-resolution format. Here's what happens when a CD is created:

  • Music is sampled 44,100 times per second. The samples are 2  (16 bits) long.
  • Separate samples are taken for the left and right  in a stereo system.

So a CD stores a huge number of bits for each second of music:

44,100 samples/second * 16 bits/sample * 2 channels = 1,411,200 bits per second

Let's break that down: 1.4 million bits per second equals 176,000 bytes per second. If an average song is three minutes long, then the average song on a CD consumes about 32 million bytes of space. That's a lot of space for one song, and it's especially large when you consider that over a 56K , it would take close to two hours to download that one song.

The MP3 format is a  system for music. The MP3 format helps reduce the number of bytes in a song without hurting the quality of the song's sound. The goal of the MP3 format is to compress a CD-quality song by a factor of 10 to 14 without noticably affecting the CD-quality sound. With MP3, a 32-megabyte (MB) song on a CD compresses down to about 3 MB. This lets you download a song in minutes rather than hours, and store hundreds of songs on your computer's  without taking up that much space.

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Is it possible to compress a song without hurting its quality? We use  all the time. For example, a GIF file is a compressed image. So is a JPG file. We create  to compress text. So we are familiar with compression algorithms for images and words and we know they work. To make a good compression algorithm for sound, a technique called perceptual noise shaping is used. It is "perceptual" partly because the MP3 format uses characteristics of the  to design the compression algorithm. For example:

  • There are certain sounds that the human ear cannot hear.
  • There are ...

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