How MP3 Players Work

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.