Stands for “MPEG Audio Layer-3.” MP3 is a compressed audio file format developed by the Moving Picture Experts Group (MPEG). A typical MP3 file sounds similar to the original recording, but requires significantly less disk space. MP3 files are often about one tenth the size of an uncompressed WAVE or AIFF file, which have the same audio quality as a CD.
The small file size and high fidelity of MP3 files helped popularize digital music downloads in the late 1990s and early 2000s. Instead of requiring a 40 megabyte download for a single song, the comparable MP3 file might be 4 MB. MP3s made it possible for users to download entire albums in roughly the same time it took to download a single WAV or AIFF file. For over a decade, MP3s were the most common way to store music files on computers and portable music players like the iPod.
While MP3s are still prevalent on the Internet, other file formats are now also used for audio compression. Advanced Audio Coding (AAC), for example, is used for songs on Apple’s iTunes Store. Ogg Vorbis is an open container format that is frequently used for royalty-free compression and streaming.
The MP3 File Format
An MP3 file includes a header, metadata, and compressed audio. The header includes information about the audio, such as the version of the encoding, the bitrate, and the (sample_rate|sample_rate). A high bitrate and sample rate produces better audio quality, but also a larger file size.A common MP3 compression setting is a bitrate of 128 kbps and a sample rate of 44.1 kHz. This produces a file size of roughly one megabyte per minute.
MP3 metadata provides information about the actual recording. This data is usually saved in an ID3 tag, which is a standard format supported by most hardware and software media players. The bulk of the MP3 file contents is the actual compressed audio, which is stored as binary data.