page_title: Data compression
section_title: Lossy audio compression
hierarchical_section_title: Data compression / Uses / Audio / Lossy audio compression
caption_attribution_description: English: Manowar The Power of Thy Sword (1992), frequencies of the uncompressed, 128 aoTuV, mp3 and ATRAC3 Files. Deutsch: Frequenzspektrum von Manowars 'The Power of Thy Sword' (1992) des Albums 'The Triumph of Steel', Unkomprimiert, 128er aotuV, mp3, ATRAC 3 @ 292 und 132kBit/s, Musepack ~128, LC-AAC und HE-AAC ~128 und wma auf 128kbit/s
context_page_description: In signal processing, data compression, source coding, or bit-rate reduction is the process of encoding information using fewer bits than the original representation. Any particular compression is either lossy or lossless. Lossless compression reduces bits by identifying and eliminating statistical redundancy. No information is lost in lossless compression. Lossy compression reduces bits by removing unnecessary or less important information. Typically, a device that performs data compression is referred to as an encoder, and one that performs the reversal of the process as a decoder.
  The process of reducing the size of a data file is often referred to as data compression. In the context of data transmission, it is called source coding; encoding done at the source of the data before it is stored or transmitted. Source coding should not be confused with channel coding, for error detection and correction or line coding, the means for mapping data onto a signal.
  Compression is useful because it reduces resources required to store and transmit data. Computational resources are consumed in the compression and decompression processes.
context_section_description: Lossy audio compression is used in a wide range of applications. In addition to the direct applications (MP3 players or computers), digitally compressed audio streams are used in most video DVDs, digital television, streaming media on the Internet, satellite and cable radio, and increasingly in terrestrial radio broadcasts. Lossy compression typically achieves far greater compression than lossless compression (5–20% of the original size, rather than 50–60%), by discarding less-critical data.
  The innovation of lossy audio compression was to use psychoacoustics to recognize that not all data in an audio stream can be perceived by the human auditory system. Most lossy compression reduces perceptual redundancy by first identifying perceptually irrelevant sounds, that is, sounds that are very hard to hear. Typical examples include high frequencies or sounds that occur at the same time as louder sounds. Those sounds are coded with decreased accuracy or not at all.
  Due to the nature of lossy algorithms, audio quality suffers when a file is decompressed and recompressed (digital generation loss). This makes lossy compression unsuitable for storing the intermediate results in professional audio engineering applications, such as sound editing and multitrack recording. However, they are very popular with end users (particularly MP3) as a megabyte can store about a minute's worth of music at adequate quality.
caption: Comparison of spectrograms of audio in an uncompressed format and several lossy formats. The lossy spectrograms show bandlimiting of higher frequencies, a common technique associated with lossy audio compression.
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