ReplayGain is a proposed technical standard published by David Robinson in 2001 to measure and normalize the perceived loudness 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 w ...

s such as MP3 and Ogg Vorbis. It allows

media players A media player could refer to: *Digital media player, home appliances that play digital media *Media player software, software that plays digital media *Portable media player, portable hardware that plays digital media *Windows Media Player Wi ...

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 at different loudness levels. Although this de facto standard 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 physical k ...

Operation

ReplayGain works by first performing a psychoacoustic analysis of an entire audio track or album to measure

peak level The amplitude of a periodic variable is a measure of its change in a single period (such as time or spatial period). The amplitude of a non-periodic signal is its magnitude compared with a reference value. There are various definitions of ampl ...

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 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 in the playback device.

Metadata

The original ReplayGain proposal specified an 8- byte 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 software p ...

and Ogg Vorbis use the REPLAYGAIN_* Vorbis comment 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 two ...

. Other formats such as

AAC AAC may refer to: Aviation * Advanced Aircraft, a company from Carlsbad, California * Alaskan Air Command, a radar network * American Aeronautical Corporation, a company from Port Washington, New York * American Aviation, a company from Cleveland, ...

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 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 hydrophone ...

. The SPL reference comes from a SMPTE recommendation used to calibrate playback levels in movie theaters. 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 Audio normalization is the application of a constant amount of gain to an audio recording to bring the amplitude to a target level (the norm). Because the same amount of gain is applied across the entire recording, the signal-to-noise ratio and ...

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, 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 mul ...

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 ...

. * Standard measurement algorithms for broadcast loudness monitoring applications have recently been developed by the International Telecommunication Union (

ITU-R BS.1770 Loudness, K-weighted, relative to full scale (LKFS) is a standard loudness measurement unit used for audio normalization in broadcast television systems and other video and music streaming services. LKFS is standardized in ITU-R BS.1770. In March ...

) and the European Broadcasting Union (

EBU R128 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. ...

Implementations

Audio players

* AIMP, Windows, Android - can write and read *

Amarok Amarok may refer to: Music * Amarok (band), a Spanish progressive rock band * ''Amarok'' (Mike Oldfield album), 1990 * ''Amarok'' (Nargaroth album), 2000 * ''Amarok'', 2010 album by Francisco López (musician) Other uses * Amarok (wolf), in In ...

KDE KDE is an international Free software movement, free software community that develops free and open-source software. As a central development hub, it provides tools and resources that allow collaborative work on this kind of software. Well-know ...

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), an open-source media player Ships * List of ships named ''Audacious'' * HMS ''Audacious'', various ships of the British Royal Navy * ''Audaci ...

, Unix-like systems and Windows * Aqualung Music Player, Linux and Windows * Banshee, Linux * Clementine, Windows, Mac OS X and Linux * cmus, Unix-like systems * Cue Broadcast Audio Player, Windows * DeaDBeeF, Linux, *BSD, OpenSolaris and Mac OS X * Exaile, 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, Windows * JavaTunes, Windows, Linux and Mac OS X *

Kodi KODI (1400 AM) is a radio station broadcasting a news/talk format. Licensed to Cody, Wyoming, United States, the station is currently owned by the Big Horn Radio Network, a division of Legend Communications of Wyoming, LLC, and features programm ...

, cross-platform * MediaMonkey, Windows * Mixxx 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 performance ...

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

Muine Muine is an audio player for the GNOME desktop environment which runs on Linux, Solaris, BSD and other UNIX-like systems. Muine is written in C# using Mono and Gtk#. The default backend is GStreamer framework but Muine can also use xine libra ...

, GNOME desktop environment * MusicBee, Windows * Nightingale, Linux, Mac OS X, Windows * Play, Mac OS X * Pocket Player, Windows Mobile, through the ReplayGain DSP plugin * ProppFrexx ONAIR, Windows * Pulsar+, Android * Qmmp, cross-platform *

Quod Libet A quodlibet (; Latin for "whatever you wish" from ''quod'', "what" and '' libet'', "pleases") is a musical composition that combines several different melodies—usually popular tunes—in counterpoint, and often in a light-hearted, humorous manne ...

, Unix-like systems. Reads ReplayGain metadata natively. Has a plugin to analyze and write ReplayGain information. *

QuuxPlayer QuuxPlayer is a freeware audio player for Windows developed by Matthew Hamilton of Quux Software. It is designed principally for sound quality, simplicity and ease of use. QuuxPlayer can support large music libraries of 100,000 tracks or more, w ...

, Windows * RadioBOSS, Windows radio automation software * Rhythmbox, GNOME (through a plug-in) * Songbird, Windows and Mac OS X * SoX, cross-platform * Squeezebox hardware and accompanying SlimServer/

SqueezeCenter 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 ...

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 d ...

* VLC media player, multiplatform. Reads ReplayGain metadata natively * Winamp, Windows *

XMMS X Multimedia System (XMMS) is an audio player (software), audio player for Unix-like systems released under a free software license. History XMMS was originally written as ''X11Amp'' by Peter and Mikael Alm in November 1997. The player was made t ...

, Unix-like systems with X11. 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 form ...

, Windows * Zortam Mp3 Media Studio, Windows

Portable media players

* All devices with a working Rockbox port * Sandisk Sansa Fuze 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

* DeaDBeeF *

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 Windows users to download music from an iTunes music share over a network, circumventing restrictions in iTunes that only allow streaming music. The software was widely popular on college campuses a ...

* PowerAMP * Vanilla Music * Winamp PRO for Android * Vinyl Music Player * XenoAmp Music Player * Musicolet Music Player Pro

Scanners

beaTunes {{Infobox Software , name = beaTunes , developer = tagtraum industries incorporated , released = {{Start date and age, df=yes, 2006, 08 , operating system = Mac OS X, Microsoft Windo ...

: 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 In classical logic, intuitionistic logic and similar logical systems, the principle of explosion (, 'from falsehood, anything ollows; or ), or the principle of Pseudo-Scotus, is the law according to which any statement can be proven from a co ...

: 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: Encoder writes metadata to LAME tag * MediaMonkey: ''Analyze Volume'' calculates RG values and writes them into the files as tags and into its library database * MP3Gain: (open source) generates metadata. Can directly modify original file and write undo information as metadata. *

for Windows: calculates gain values and saves them in its library database; optionally writes ReplayGain tags to files with ID3v2 tags. *

: Based on

. 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. * Winamp: 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

Notes

References

{{reflist, colwidth=30em

External links

ReplayGain specification

ReplayGain
at Hydrogenaudio wiki
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