MPEG-1 and/or MPEG-2 Audio Layer III,[4] more commonly referred to as MP3, is an audio coding format for digital audio which uses a form of lossy data compression. It is a common audio format for consumer audio streaming or storage, as well as a de facto standard of digital audio compression for the transfer and playback of music on most digital audio players and computing devices.
The use of lossy compression is designed to reduce by a factor of 10 the amount of data required to represent digital audio recordings yet still sound like the original uncompressed audio to most listeners.
Compared to CD quality digital audio, MP3 compression commonly achieves 75 to 95% reduction in size. MP3 files are thus 1/4 to 1/20 the size of the original digital audio stream. This is important for both transmission and storage concerns. The basis for such comparison is the CD-ROM digital audio format which requires 1411200 bit/s. A commonly used MP3 encoding setting is CBR 128 kbit/s resulting in file size 1/ 11 (=9% or 91% compression) of the original CD-quality file.[7]
The MP3 lossy compression works by reducing (or approximating) the accuracy of certain parts of a continuous sound that are considered to be beyond the auditory resolution ability of most people. This method is commonly referred to as perceptual coding.[8] It uses psychoacoustic models to discard or reduce precision of components less audible to human hearing, and then records the remaining information in an efficient manner.
MP3 was designed by the Moving Picture Experts Group (MPEG) as part of its MPEG-1 standard and later extended in the MPEG-2 standard. The first subgroup for audio was formed by several teams of engineers at Fraunhofer IIS, University of Hanover, AT&T-Bell Labs, Thomson-Brandt, CCETT, and others.[9] MPEG-1 Audio (MPEG-1 Part 3), which included MPEG-1 Audio Layer I, II and III was approved as a committee draft of ISO/IEC standard in 1991,[10][11] finalised in 1992[12] and published in 1993 (ISO/IEC 11172-3:1993[5]). A backwards compatible MPEG-2 Audio (MPEG-2 Part 3) extension with lower sample and bit rates was published in 1995 (ISO/IEC 13818-3:1995).[6][13]
MP3 is a streaming or broadcast format (as opposed to a file format) meaning that individual frames can be lost without affecting the ability to decode successfully delivered frames. Storing an MP3 stream in a file enables time shifted playback.
