ReplayGain is a proposed

technical standard A technical standard is an established norm or requirement for a repeatable technical task which is applied to a common and repeated use of rules, conditions, guidelines or characteristics for products or related processes and production methods, ...

published by David Robinson in 2001 to measure and normalize the perceived

loudness In acoustics, loudness is the subjective perception of sound pressure. More formally, it is defined as, "That attribute of auditory sensation in terms of which sounds can be ordered on a scale extending from quiet to loud". The relation of ph ...

of audio in computer

audio format An audio format is a medium for sound recording and reproduction. The term is applied to both the physical recording media and the recording formats of the audio content—in computer science it is often limited to the audio file format, but its ...

s such as

MP3 MP3 (formally MPEG-1 Audio Layer III or MPEG-2 Audio Layer III) is a coding format for digital audio developed largely by the Fraunhofer Society in Germany, with support from other digital scientists in the United States and elsewhere. Origin ...

and

Ogg Vorbis Vorbis is a free and open-source software project headed by the Xiph.Org Foundation. The project produces an audio coding format and software reference encoder/decoder (codec) for lossy audio compression. Vorbis is most commonly used in conjun ...

. It allows media players to normalize loudness for individual tracks or albums. This avoids the common problem of having to manually adjust volume levels between tracks when playing audio files from albums that have been

mastered Mastering, a form of audio post production, is the process of preparing and transferring recorded audio from a source containing the final mix to a data storage device (the master), the source from which all copies will be produced (via meth ...

at different loudness levels. Although this

de facto standard A ''de facto'' standard is a custom or convention that has achieved a dominant position by public acceptance or market forces (for example, by early entrance to the market). is a Latin phrase (literally " in fact"), here meaning "in practice b ...

is now formally known as ReplayGain, it was originally known as Replay Gain and is sometimes abbreviated RG. ReplayGain is supported in a large number of media software and

portable devices A mobile device (or handheld computer) is a computer small enough to hold and operate in the hand. Mobile devices typically have a flat LCD or OLED screen, a touchscreen interface, and digital or physical buttons. They may also have a physic ...

Operation

ReplayGain works by first performing a

psychoacoustic Psychoacoustics is the branch of psychophysics involving the scientific study of sound perception and audiology—how humans perceive various sounds. More specifically, it is the branch of science studying the psychological responses associated wit ...

analysis of an entire audio track or album to measure peak level and perceived loudness.

Equal-loudness contour An equal-loudness contour is a measure of sound pressure level, over the frequency spectrum, for which a listener perceives a constant loudness when presented with pure steady tones. The unit of measurement for loudness levels is the phon and ...

s are used to compensate for frequency effects and statistical analysis is used to accommodate for effects related to time. The difference between the measured perceived loudness and the desired target loudness is calculated; this is considered the ideal replay

gain Gain or GAIN may refer to: Science and technology * Gain (electronics), an electronics and signal processing term * Antenna gain * Gain (laser), the amplification involved in laser emission * Gain (projection screens) * Information gain in de ...

value. Typically, the replay gain and peak level values are then stored as

metadata Metadata is "data that provides information about other data", but not the content of the data, such as the text of a message or the image itself. There are many distinct types of metadata, including: * Descriptive metadata – the descriptive ...

in the audio file. ReplayGain-capable audio players use the replay gain metadata to automatically

attenuate In physics, attenuation (in some contexts, extinction) is the gradual loss of flux intensity through a medium. For instance, dark glasses attenuate sunlight, lead attenuates X-rays, and water and air attenuate both light and sound at vari ...

or amplify the signal on a per-track or per-album basis such that tracks or albums play at a similar loudness level. The peak level metadata can be used to prevent gain adjustments from inducing

clipping Clipping may refer to: Words * Clipping (morphology), the formation of a new word by shortening it, e.g. "ad" from "advertisement" * Clipping (phonetics), shortening the articulation of a speech sound, usually a vowel * Clipping (publications) ...

in the playback device.

Metadata

The original ReplayGain proposal specified an 8-

byte The byte is a unit of digital information that most commonly consists of eight bits. Historically, the byte was the number of bits used to encode a single character of text in a computer and for this reason it is the smallest addressable uni ...

field in the header of any file. Most implementations now use tags for ReplayGain information.

FLAC FLAC (; Free Lossless Audio Codec) is an audio coding format for lossless compression of digital audio, developed by the Xiph.Org Foundation, and is also the name of the free software project producing the FLAC tools, the reference softwa ...

and Ogg Vorbis use the REPLAYGAIN_*

Vorbis comment A Vorbis comment is a metadata container used in the Vorbis, FLAC, Theora, Speex and Opus file formats. It allows information such as the title, artist, album, track number or other information about the file to be added to the file itself. Howeve ...

fields. MP3 files usually use

ID3v2 ID3 is a metadata container most often used in conjunction with the MP3 audio file format. It allows information such as the title, artist, album, track number, and other information about the file to be stored in the file itself. There are tw ...

. Other formats such as AAC and WMA use their native tag formats with a specially formatted tag entry listing the track's replay gain and peak loudness. ReplayGain utilities usually add metadata to the audio files without altering the original audio data. Alternatively, a tool can amplify or attenuate the data itself and save the result to another, gain-adjusted audio file; this is not perfectly reversible in most cases. Some lossy audio formats, such as MP3, are structured in a way that they encode the volume of each compressed frame in a stream, and tools such as

MP3Gain MP3Gain is an audio normalization software tool. The tool is available on multiple platforms and is free software. It analyzes the MP3 and reversibly changes its volume. The volume can be adjusted for single files or as album where all files woul ...

take advantage of this for directly applying the gain adjustment to MP3 files, adding undo information so that the process is reversible.

Target loudness

The target loudness of ReplayGain utilities is 89 dB

sound pressure level Sound pressure or acoustic pressure is the local pressure deviation from the ambient (average or equilibrium) atmospheric pressure, caused by a sound wave. In air, sound pressure can be measured using a microphone, and in water with a hydropho ...

. The SPL reference comes from a

SMPTE The Society of Motion Picture and Television Engineers (SMPTE) (, rarely ), founded in 1916 as the Society of Motion Picture Engineers or SMPE, is a global professional association of engineers, technologists, and executives working in the m ...

recommendation used to calibrate playback levels in

movie theaters A movie theater (American English), cinema (British English), or cinema hall (Indian English), also known as a movie house, picture house, the movies, the pictures, picture theater, the silver screen, the big screen, or simply theater is a ...

. A more common means of specifying a reference level is relative to a full-scale signal. ReplayGain nominally plays at -14 dB relative to full-scale leaving 14 dB of headroom for reproduction of dynamic material. In contrast, the SMPTE RP 200:2002, on which the ReplayGain reference was originally based, recommends 20 dB of headroom. The more recent

EBU R 128 EBU R 128 is a recommendation for loudness normalisation and maximum level of audio signals. It is primarily followed during audio mixing of television and radio programmes and adopted by broadcasters to measure and control programme loudness. ...

suggests 23 dB.

Track-gain and album-gain

ReplayGain analysis can be performed on individual tracks, so that all tracks will be of equal volume on playback. Analysis can also be performed on a per-album basis. In album-gain analysis an additional peak-value and gain-value, which will be shared by the whole album, is calculated. Using the album-gain values during playback will preserve the volume differences among tracks on an album. On playback, listeners may decide if they want all tracks to sound equally loud or if they want all albums to sound equally loud with different tracks having different loudness. In album-gain mode, when album-gain data is missing, players should use track-gain data instead.

Alternatives

* Peak amplitude is not a reliable indicator of loudness, so consequently peak normalization does not offer reliable normalization of perceived loudness. RMS normalization is more accurate, but does not take into account psychoacoustic aspects of loudness perception. * With

dynamic range compression Dynamic range compression (DRC) or simply compression is an audio signal processing operation that reduces the volume of loud sounds or amplifies quiet sounds, thus reducing or ''compressing'' an audio signal's dynamic range. Compression is ...

, volume may be altered on-the-fly on playback producing a variable-gain normalization, as opposed to the constant gain as rendered by ReplayGain. While dynamic range compression is beneficial in keeping volume constant, it changes the artistic intent of the recording. * ''Sound Check'' is a proprietary Apple Inc. technology similar in function to ReplayGain. It is available in

iTunes iTunes () is a software program that acts as a media player, media library, mobile device management utility, and the client app for the iTunes Store. Developed by Apple Inc., it is used to purchase, play, download, and organize digital mu ...

and on the

iPod The iPod is a discontinued series of portable media players and multi-purpose mobile devices designed and marketed by Apple Inc. The first version was released on October 23, 2001, about months after the Macintosh version of iTunes wa ...

. * Standard measurement algorithms for broadcast

loudness monitoring Loudness monitoring of programme levels is needed in radio and television broadcasting, as well as in audio post production. Traditional methods of measuring signal levels, such as the Peak programme meter and VU meter, do not give the subjective ...

applications have recently been developed by the

International Telecommunication Union The International Telecommunication Union is a specialized agency of the United Nations responsible for many matters related to information and communication technologies. It was established on 17 May 1865 as the International Telegraph Unio ...

( ITU-R BS.1770) and the European Broadcasting Union ( EBU R128).

Implementations

Audio players

* AIMP, Windows, Android - can write and read * Amarok, KDE desktop environment. Native ReplayGain support was added in Amarok 2.1. *

Audacious Audacious may refer to: * ''Audacious'' (album), a 2016 album by Cupcakke * Audacious (software) Audacious is a Free and open-source software, free and open-source audio player software with a focus on low resource use, high audio quality, ...

Unix-like A Unix-like (sometimes referred to as UN*X or *nix) operating system is one that behaves in a manner similar to a Unix system, although not necessarily conforming to or being certified to any version of the Single UNIX Specification. A Unix-li ...

systems and Windows * Aqualung Music Player, Linux and Windows *

Banshee A banshee ( ; Modern Irish , from sga, ben síde , "woman of the fairy mound" or "fairy woman") is a female spirit in Irish folklore who heralds the death of a family member, usually by screaming, wailing, shrieking, or keening. Her name i ...

, Linux *

Clementine A clementine (''Citrus × clementina'') is a tangor, a citrus fruit hybrid between a willowleaf mandarin orange ( ''C.'' × ''deliciosa'') and a sweet orange (''C. × sinensis''), named in honor of Clément Rodier, a French missionary who fir ...

, Windows, Mac OS X and Linux * cmus, Unix-like systems * Cue Broadcast Audio Player, Windows *

DeaDBeeF DeaDBeeF is an audio player software available for Linux, Android and other Unix-like operating systems. DeaDBeeF is free and open-source software, except on Android. History The player was first published in August 2009. Its author cited ...

, Linux, *BSD, OpenSolaris and Mac OS X *

Exaile Exaile is a cross-platform free and open-source audio player, tag editor and library organizer. It was originally conceived to be similar in style and functions to KDE's Amarok 1.4, but uses the GTK widget toolkit rather than Qt. It is writte ...

, Linux/

GNOME A gnome is a mythological creature and diminutive spirit in Renaissance magic and alchemy, first introduced by Paracelsus in the 16th century and later adopted by more recent authors including those of modern fantasy literature. Its characte ...

desktop environment *

, the reference FLAC decoder can create a new copy with ReplayGain applied, through the undocumented option --apply-replaygain-which-is-not-lossless as of version 1.1.1 *

foobar2000 foobar2000 (often abbreviated as fb2k or f2k) is a freeware audio player for Microsoft Windows, iOS and Android developed by Peter Pawłowski. It has a modular design, which provides user flexibility in configuration and customization. Stan ...

, Windows * hunisPRO automation system, Windows *

JRiver Media Center JRiver Media Center is a multimedia application that allows the user to play and organize various types of media on a computer running Windows, macOS, or Linux operating systems. JRiver Media Center is a "jukebox"-style media player, like iTu ...

, Windows * JavaTunes, Windows, Linux and Mac OS X * Kodi, cross-platform *

MediaMonkey MediaMonkey is a digital media player and media library application developed by Ventis Media Inc., for organizing and playing audio on Microsoft Windows and Android operating systems. MediaMonkey for Windows (sometimes noted as MMW) include ...

, Windows *

Mixxx Mixxx is free and open-source software for DJing.James, Daniel. "Drafting Digital Media". Apress, 2009, p. 213. It is cross-platform and supports most common music file formats. Mixxx can be controlled with MIDI and HID controllers and timecode ...

virtual DJ software, v1.9.0 and up * madplay, Unix-like systems *

Mpg123 mpg123 is a free and open-source audio player. It supports MPEG audio formats, including MP3. As a console application, it has no graphical user interface. mpg123's Assembly code is optimized with SIMD instructions to improve the performanc ...

, supported for only Xing/Lame/Info header * mpv, multiplatform. Can read ReplayGain tags * MPD, Unix-like systems * Muine, GNOME desktop environment *

MusicBee MusicBee is a freeware media player for playback and organization of audio files on Microsoft Windows, built using the audio library. Features * Audio playback: MP3, AAC, M4A, MPC, OGG, FLAC, ALAC, APE, Opus, , WavPack, WMA, WAV, MI ...

, Windows *

Nightingale The common nightingale, rufous nightingale or simply nightingale (''Luscinia megarhynchos''), is a small passerine bird best known for its powerful and beautiful song. It was formerly classed as a member of the thrush family Turdidae, but is no ...

, Linux, Mac OS X, Windows * Play, Mac OS X * Pocket Player, Windows Mobile, through the ReplayGain DSP plugin * ProppFrexx ONAIR, Windows * Pulsar+, Android *

Qmmp qmmp (for ''Qt-based MultiMedia Player'') is a free and open-source cross-platform audio player that is similar to Winamp. It is written in C++ using the Qt widget toolkit for the user interface. It officially supports the operating systems Lin ...

, cross-platform * Quod Libet, Unix-like systems. Reads ReplayGain metadata natively. Has a plugin to analyze and write ReplayGain information. * QuuxPlayer, Windows * RadioBOSS, Windows radio automation software *

Rhythmbox Rhythmbox is a free and open-source audio player software, tag editor and music organizer for digital audio files on Linux and Unix-like systems. Rhythmbox is designed to work well under GNOME, but can function on other desktop environments. I ...

, GNOME (through a plug-in) *

Songbird A songbird is a bird belonging to the suborder Passeri of the perching birds (Passeriformes). Another name that is sometimes seen as the scientific or vernacular name is Oscines, from Latin ''oscen'', "songbird". The Passeriformes contains 5000 ...

, Windows and Mac OS X * SoX, cross-platform *

Squeezebox The term squeezebox (also squeeze box, squeeze-box) is a colloquial expression referring to any musical instrument of the general class of hand-held bellows-driven free reed aerophones such as the accordion and the concertina. The term is so a ...

hardware and accompanying

SlimServer Logitech Media Server (formerly SlimServer, SqueezeCenter and Squeezebox Server) is a streaming audio server supported by Logitech (formerly Slim Devices), developed in particular to support their Squeezebox (network music player), Squeezebox rang ...

/ SqueezeCenter software from

Slim Devices Slim Devices, Inc. was a consumer electronics company based in Mountain View, California, United States. Their main product was the Squeezebox network music player which connects to a home ethernet or Wi-Fi network, and allows the owner to stream ...

VLC media player VLC media player (previously the VideoLAN Client and commonly known as simply VLC) is a free and open-source, portable, cross-platform media player software and streaming media server developed by the VideoLAN project. VLC is available for desk ...

, multiplatform. Reads ReplayGain metadata natively *

Winamp Winamp is a media player for Microsoft Windows originally developed by Justin Frankel and Dmitry Boldyrev by their company Nullsoft, which they later sold to AOL in 1999 for $80 million. It was then acquired by Radionomy in 2014. Since ve ...

, Windows * XMMS, Unix-like systems with

X11 The X Window System (X11, or simply X) is a windowing system for bitmap displays, common on Unix-like operating systems. X provides the basic framework for a GUI environment: drawing and moving windows on the display device and interacting wi ...

. Supports ReplayGain for Vorbis; for MP3 files, a patched version of the xmms-mad plugin which only supports APEv2 is available) * XMMS2, Unix-like systems *

XMPlay XMPlay is a freeware audio player for Windows. Initially released in 1998, it is often used as a reference player for tracker audio files. Overview Developed by ''Un4seen Developments'' in 1998, it originally only supported the XM file fo ...

, Windows * Zortam Mp3 Media Studio, Windows

Portable media players

* All devices with a working Rockbox port *

Sandisk SanDisk is a brand for flash memory products, including memory cards and readers, USB flash drives, solid-state drives, and digital audio players, manufactured and marketed by Western Digital. The original company, SanDisk Corporation was acquir ...

Sansa Fuze The Sansa Fuze is a portable media player developed by SanDisk and released on March 8, 2008. The Fuze is available in three different Flash memory capacities: 2 GB, 4 GB, and 8 GB and comes in six different colors: black, blue, pi ...

and Sansa Clip+ * iPod through other programs that convert ReplayGain data to the Apple proprietary Sound Check format (e.g. iPod Manager for

, other alternatives elsewhere on this page) Typical CD players and other legacy audio players do not support ReplayGain.

Android compatible players

for Android * GoneMAD Music Player *

Neutron Music Player The neutron is a subatomic particle, symbol or , which has a neutral (not positive or negative) charge, and a mass slightly greater than that of a proton. Protons and neutrons constitute the nuclei of atoms. Since protons and neutrons behave ...

* Muzio Player *

MyTunes myTunes is a program that originally allowed Microsoft Windows, Windows users to download music from an iTunes music share over a network, circumventing restrictions in iTunes that only allow Streaming media, streaming music. The software was wid ...

* PowerAMP * Vanilla Music *

PRO for Android * Vinyl Music Player * XenoAmp Music Player * Musicolet Music Player Pro

Scanners

* beaTunes: Writes the standard replaygain_track_gain/replaygain_track_peak tags and replaces the iTunNORM metadata tag value, which is used by

software and

music players for Sound Check volume normalization. * Ex Falso: Included plugin scans files on a per-album base, writes the standard tags into metadata. *

and metaflac: Encoder can optionally generate metadata. Tagger generates metadata. *

: Generates metadata through included plugin using EBU R128 (but at old 89 dB levels) for all supported tag formats. *

LAME Lame or LAME may refer to: Music * "Lame" (song) by Unwritten Law * ''Lame'' (album) by Iame People * Ibrahim Lame (born 1953), Nigerian educator and politician * Jennifer Lame (), American film editor * Quintín Lame (1880–1967), Colombian ...

: Encoder writes metadata to LAME tag *

: ''Analyze Volume'' calculates RG values and writes them into the files as tags and into its library database *

: (open source) generates metadata. Can directly modify original file and write undo information as metadata. * QuuxPlayer for Windows: calculates gain values and saves them in its library database; optionally writes ReplayGain tags to files with ID3v2 tags. * Quod Libet: Based on Ex Falso. Generates metadata through included plugin to analyze and write ReplayGain information * Rapid Evolution: Generates metadata * soundKonverter: frontend for various audio conversion tools. Is built using KDE Development Platform and has a ReplayGain tool. *

: Generates metadata * loudgain: A ReplayGain 2.0 loudness normalizer, based on the EBU R128/ITU BS.1770 standard (-18 LUFS) and supports FLAC/Ogg/MP2/MP3/MP4/M4A/ALAC/Opus/ASF/WMA/WAV/WavPack/AIFF/APE audio files. It uses the MP3gain command-line syntax but does not modify the actual audio data.

Streaming

Spotify Spotify (; ) is a proprietary Swedish audio streaming and media services provider founded on 23 April 2006 by Daniel Ek and Martin Lorentzon. It is one of the largest music streaming service providers, with over 456 million monthly active use ...

Notes

References

{{reflist, colwidth=30em

External links

ReplayGain specification

ReplayGain
at Hydrogenaudio

wiki A wiki ( ) is an online hypertext publication collaboratively edited and managed by its own audience, using a web browser. A typical wiki contains multiple pages for the subjects or scope of the project, and could be either open to the pub ...

Replay Gain – A Proposed Standard
the original proposal, now out of date with respect to current practice

— guide to using graphical and command line ReplayGain tools in Linux. Computer standards Digital audio