MP3 or MPEG 1 Audio Layer 3 is a lossy encoding format. Like many MPEG formats, it is designed to lose data while seeming to a person to be an acceptible representation of the original track.

This works by discarding data that is inaudible, or not important to the general perceived sound, and then losslessly compressing the result.

The MP3 format was first published in 1993, however it wasn’t until 1994 that Fraunhofer released an MP3 encoder to the public. In 1995 the first MP3 player capable of real-time decoding and play was released, this was Winplay3 – thus MP3 only began to gain in popularity in the years following, also based on a new and widespread trend of music filesharing over the internet.

Generally MP3 is designed to play songs encoded with a bitrate within a range of 128 to 320 kbits/second, with the design reference being a 128 kbit/second copy of Suzanne Vega’s Tom’s Diner. The practical average of general use has gone up over the years, and variable bit rate mode has been introduced, increasing the average general quality of an MP3 since it was first introduced and used in 1995.

The encoder used is quite important to the playback quality of an MP3, as there are various ways of encoding an MP3. Generally the open source MP3 encoder LAME is considered to be the best MP3 encoder for not only quality but speed of encoding as well.

MP3s are generally encoded with ID3 or ID3v2 metadata, as well as various other non-standard metadata formats, including ReplayGain – which adjusts/normalizes the volume of a song.

Problems with MP3

While MP3 is the undisputed king of audio formats in modern use, there are several limitations and problems with the format that have led some to choose alternatives such as Ogg, AAC, and FLAC.

• MP3 is always lossy, meaning that it will always sound worse than a CD and becomes a poor source for another round of compression. Within the standard the bitrate cannot go above 320kbit. (LAME is capable of encoding at double this, but the results may not be playable on many players)
• MP3 play is limited to 2 channels, which especially inconvenient for multi-channel audio such as DVD’s AC3 audio files.
• There is no provision for gapless or gap defined tracks play. (LAME can circumvent this with non-standard metadata, but not all players will recognize this).
• Although a subjective science, MP3 is widely considered to be obsolete in terms of sound quality for bitrate, being succeeded by newer codecs such as Ogg and AAC, which are widely claimed to achieve sound parity in fewer bits.
• MP3 is a patent encumbered format, the Frauenhofer Society claims that they own a patent on MP3 encoding and decoding software, and demanded software developers obtain their permission to develop MP3 software. (In 2010 these patents will expire)

MP3 projects

• mod_mp3 – an Apache module for MP3
• icecast – a server for streaming MP3

• XMMS
• foobar2000
• amaroK – KDE media player

• LAME – the gold standard MP3 encoder