Editing ReplayGain

{{short description|Loudness normalization system}}

'''ReplayGain''' is a proposed [[technical standard]] published by David Robinson in 2001 to measure and [[Audio normalization|normalize]] the perceived [[loudness]] of audio in computer [[audio format]]s such as [[MP3]] and [[Ogg Vorbis]]. It allows [[Media player (disambiguation)|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]] at different loudness levels.

Although this [[de facto standard]] is now formally known as ReplayGain,<ref>{{citation |url=http://www.hydrogenaud.io/forums/index.php?s=&showtopic=85536&view=findpost&p=736023 |title=ReplayGain Specification discussion |author=David Robinson |publisher=Hydrogenaudio |date=2010-12-17 |access-date=2011-07-12}}</ref> it was originally known as '''Replay Gain''' and is sometimes abbreviated '''RG'''.

ReplayGain is supported in a large number of [[media player (software)|media software]] and [[portable media player|portable devices]].

==Operation==
ReplayGain works by first performing a [[psychoacoustic]] analysis of an entire audio track or album to measure [[dBFS|peak level]] and perceived loudness. [[Equal-loudness contour]]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 (electronics)|gain]] value. Typically, the replay gain and peak level values are then stored as [[metadata]] 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 (audio)|clipping]] in the playback device.<ref>{{citation |url=http://wiki.hydrogenaud.io/index.php?title=ReplayGain_specification#Clipping_prevention |title=ReplayGain specification |access-date=2011-04-15}}</ref>

===Metadata===
The original ReplayGain proposal specified an 8-[[byte]] field in the header of any file. Most implementations now use [[Tag (metadata)|tags]] for ReplayGain information. [[FLAC]] and Ogg Vorbis use the <code>REPLAYGAIN_*</code> [[Vorbis comment]] fields. MP3 files usually use [[ID3v2]].  Other formats such as [[Advanced Audio Coding|AAC]] and [[Windows Media Audio|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 is specified as the loudness of a stereo [[pink noise]] signal played back at 89&nbsp;dB [[sound pressure level]] or −14&nbsp;dB [[DBFS|relative to full scale]].<ref>{{citation |title=ReplayGain 1.0 specification |url=https://wiki.hydrogenaud.io/index.php?title=ReplayGain_specification#Reference_level |access-date=2023-09-17 |website=Hydrogenaudio Knowledgebase}}</ref> This is based on [[SMPTE]] recommendation RP&nbsp;200:2002, which specifies a similar method for calibrating playback levels in [[movie theaters]] using a reference level 6&nbsp;dB lower (83&nbsp;dB SPL, −20&nbsp;dBFS).{{#tag:ref|Although the original ReplayGain proposal used the 83&nbsp;dB SPL reference level unchanged, an early departure from the proposal to 89&nbsp;dB SPL was endorsed by its author.<ref>{{citation|url=http://www.hydrogenaud.io/forums/index.php?s=&showtopic=83397&view=findpost&p=721854 |title=Does Replay gain work differtly {{sic|nolink=y}} in Media monkey |publisher=Hydrogenaudio |date=2010-10-07 |access-date=2010-12-30}}</ref>|group="note"}}

=== 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. [[Root mean square|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]] and on the [[iPod]].<ref>{{citation|url=http://ipod.about.com/od/itunes/g/soundcheck_def.htm |title=Using Sound Check with iPod |publisher=About.com |author=Sam Costello |access-date=2010-05-11}}</ref>
* Standard measurement algorithms for broadcast [[loudness monitoring]] applications have recently been developed by the [[International Telecommunication Union]] ([[ITU-R BS.1770]]) and the [[European Broadcasting Union]] ([[EBU R128]]).<ref name="ebur128">{{citation |author=EBU |author-link=European Broadcasting Union |date=August 2011 |title=Loudness normalisation and permitted maximum level of audio signals |url=http://tech.ebu.ch/docs/r/r128.pdf}}</ref> This new method has been used to measure loudness in newer ReplayGain utilities such as [[foobar2000]] (since 1.1.6)<ref group="lower-alpha" name="foobar"/> and loudgain.<ref group="lower-alpha" name=loudgain/>

== Implementations ==
{| class="wikitable sortable"
! Name !! Platforms !! Can write !! class="unsortable" | {{abbr|Ref.|reference}}
|-
| [[AIMP]] || {{csl|Windows|Android}} || {{yes}} || {{refn|group=lower-alpha|<ref group="lower-alpha">{{citation|url=https://www.aimp.ru/?do=features|title=Main features and Functions|website=[[AIMP]] for Windows|access-date=2023-02-25}}</ref><ref group="lower-alpha">{{citation|url=https://www.aimp.ru/?do=features&os=android|title=Main features and functionality|website=[[AIMP]] for Android}}</ref>}}
|-
| [[Amarok (software)|Amarok]] || {{csl|Linux|NetBSD|FreeBSD|macOS|Windows}} || {{yes}} || <ref group="lower-alpha">{{citation|url=http://padoca.wordpress.com/2009/02/15/amarok-21-back-to-the-future-english-version/ |title=Amarok 2.1 – back to the future |publisher=Padoca |date=2009-02-15 |access-date=2010-12-30}}</ref>
|-
|Amberol
|Linux|| {{no}} || <ref group="lower-alpha">{{Cite web |date=2022-07-25 |title=ReplayGain support (!100) · Merge requests · World / amberol · GitLab |url=https://gitlab.gnome.org/World/amberol/-/merge_requests/100 |access-date=2024-03-15 |website=GitLab |language=en}}</ref>
|-
| [[Audacious (software)|Audacious]] || {{csl|Linux|Windows}} || {{no}}
|
|-
| [[Banshee (media player)|Banshee]] || {{csl|Linux|macOS (beta)|Windows (alpha)}} || {{yes}} || <ref group="lower-alpha">{{citation|url=https://gitlab.gnome.org/Archive/banshee/-/raw/master/extras/YeOldeChangeLog|title=YeOldeChangeLog|website=[[GitLab]]}}</ref>
|-
| [[beaTunes]] || {{csl|macOS|Windows}} || {{yes}} || <ref group="lower-alpha">{{Citation |title=beaTunes |url=https://www.beatunes.com/en/itunes-replay-gain.html |access-date=2023-08-29 |language=en |quote=beaTunes allows you to perform the ReplayGain analysis and adjust the standardized, track-specific id3 tags}}</ref>
|-
| BTR Amp || {{csl|iOS/iPadOS}} || {{no}} || <ref group="lower-alpha">{{citation|url=https://btrlabs.com/btr-amp-v13-volume-normalization-replaygain-and-sound-check/|title=BTR AMP v13.0 – Volume Normalization – ReplayGain and Sound Check|website=BTR Labs|date=2022-04-07|access-date=2023-04-06}}</ref>
|-
| [[Clementine (software)|Clementine]] || {{csl|Linux|macOS|(32-bit) Windows}} || {{no}} ||
|-
| cmus || [[Unix-like]] || {{yes}} ||
|-
| [[DeaDBeeF]] || {{csl|Linux|macOS|Windows|Unix-like}} || {{yes}} || <ref group="lower-alpha">{{citation|url=https://deadbeef.sourceforge.io/|title=DeaDBeeF – The Ultimate Music Player|access-date=2023-04-06|website=[[SourceForge]]}}</ref>
|-
| [[Exaile]] || {{csl|Linux|Windows|macOS}} || {{no}} ||
|-
| [[Ex Falso (software)|Ex Falso]]/[[Quod Libet (software)|Quod Libet]] || {{csl|Linux|Windows|macOS}} || {{yes}} || <ref group="lower-alpha">{{citation|url=https://quodlibet.readthedocs.io/en/latest/guide/playback/replaygain.html|title=Replay Gain|website=Quod Libet|access-date=2023-04-06}}</ref>
|-
| [[foobar2000]] || {{csl|Windows|iOS/iPadOS|Android|macOS}} || {{yes}} || <ref group="lower-alpha" name="foobar">{{citation |title=Foobar2000:Preferences:ReplayGain Scanner – Hydrogenaudio Knowledgebase |url=https://wiki.hydrogenaud.io/index.php?title=Foobar2000:Preferences:ReplayGain_Scanner |website=wiki.hydrogenaud.io}}</ref>
|-
| [[JRiver Media Center]] || {{csl|Windows|macOS|Linux}} || {{yes}} || <ref group="lower-alpha">{{citation|url=https://wiki.jriver.com/index.php/Replay_Gain_Adjustment|title=Replay Gain Adjustment|website=JRiverWiki|access-date=2023-04-06}}</ref>
|-
| JavaTunes || {{csl|Java}} || {{no}} ||
|-
| [[Kodi (software)]] || {{csl|Windows|macOS|Android|iOS|tvOS|Linux|Xbox|[[*BSD]]}} || {{no}} ||
|-
| Lightweight Music Server || {{csl|[[Source code]]}} || {{yes}} || <ref group="lower-alpha">{{Citation |last=Poupon |first=Emeric |title= Web player: Replaygain support |work=lms issues |issue=38 |url=https://github.com/epoupon/lms/issues/38 |access-date=2024-01-21 |language=en}}</ref>
|-
| [[Lyrion Music Server]] || {{csl|[[Debian]]|Windows|macOS|[[RPM package]]|[[Perl]]}} || {{no}} ||
|-
| Loudgain || {{csl|Source code}} || {{yes}} || <ref name="loudgain" group="lower-alpha">{{Citation |last=Hormann |first=Matthias C. |title=loudgain |date=2024-01-04 |url=https://github.com/Moonbase59/loudgain |access-date=2024-01-21}}</ref>
|-
| [[madplay|MAD/madplay]] || {{csl|Source code}} || {{yes}} ||
|-
| [[MediaMonkey]] || {{csl|Windows|Android}} || {{yes}} ||
|-
| [[Mixxx]]<ref group="note>Uses MAD.</ref> || {{csl|Windows|macOS|Linux}} || {{yes}} || <ref group="lower-alpha">{{citation|url=https://mixxx.org/features/|title=Features|website=Mixxx|access-date=2023-04-07|quote=Mixxx reads existing ReplayGain tags and analyzes songs that don't have them.}}</ref>
|-
| [[mp3gain]] || {{csl|Windows}} || {{yes}} || <ref group="lower-alpha">{{citation|url=https://mp3gain.sourceforge.net/|title=MP3Gain|website=Sourceforge|access-date=2023-04-07|quote=MP3Gain analyzes and adjusts mp3 files so that they have the same volume.}}</ref>
|-
| [[mpg123]] || {{csl|Linux|Windows}} || {{no}} ||
|-
| [[Music Player Daemon|MPD]] || {{csl|Windows|Linux}} || {{yes}} ||
|-
| [[Mpv (media player)|mpv]] || {{csl|Windows|macOS|Linux}} || {{no}} ||
|-
| [[Muine]] || {{csl|Linux|Unix-like}} || {{no}} || <ref group="lower-alpha">{{citation|url=https://gitlab.gnome.org/Archive/muine/-/commit/da6bec783172a84084857455aa96f8f8f492fffb|title=updated TODO again, making the direction we're heading a bit clearer|website=GitLab|date=2004-02-13}}</ref>
|-
| [[MusicBee]] || {{csl|Windows}} || {{yes}} || <ref group="lower-alpha">{{citation|url=https://getmusicbee.com/forum/index.php?topic=11200.msg73245#msg73245|title=MusicBee 2.3|date=2014-02-17}}</ref>
|-
| [[Nightingale (software)|Nightingale]] || {{csl|Linux|Windows|macOS}} || {{no}} || <ref group="lower-alpha">{{Citation |last=Giger |first=Martin |title=Normalization? |url=https://forum.getnightingale.com/thread-864.html |work=Nightingale Forum |access-date=2023-05-31 |archive-url=https://web.archive.org/web/20230508072651/https://forum.getnightingale.com/thread-864.html |quote=there is no reference of it being loaded or written to the file |archive-date=2023-05-08}}</ref>
|-
| PowerAMP || {{csl|Android}} || {{no}} ||
|-
| ProppFrexx ONAIR || {{csl|Windows}} || {{yes}} || <ref group="lower-alpha">{{Citation |title=Features |url=https://qmmp.ylsoftware.com/features.php |work=Qmmp |access-date=2023-06-01 |quote=ReplayGain scanner}}</ref>
|-
| RadioBOSS || {{csl|Windows}} || {{yes}} ||
|-
| [[Rockbox]] || {{csl|[[Digital audio player]]s}} || {{yes}} ||
|-
| [[SoX]] || {{csl|Windows|Linux|macOS}} || {{yes}} ||
|-
| Vanilla Music || {{csl|Android}} || {{no}} ||
|-
| Vinyl Music Player || {{csl|Android}} || {{no}} ||
|-
| [[VLC media player]] || {{csl|Windows|[[Universal Windows Platform apps|UWP]]|macOS|iOS|[[Apple TV]]|Linux|Android|FreeBSD}} || {{no}} ||
|-
| [[Winamp]] || {{csl|Windows}} || {{yes}} ||
|-
| [[XMPlay]] || {{csl|Windows}} || {{yes}} ||
|-
| Zortam Mp3 Media Studio || {{csl|Windows|Android}} || {{maybe}}<ref group="note">Exclusive to the Pro version on Windows.</ref> ||
|}

===Streaming===
* [[Spotify]]<ref>{{citation |url=https://www.izotope.com/en/learn/mastering-for-streaming-platforms.html |publisher=iZotope |date=October 24, 2019 |author=Ian Stewart |title=Mastering for Streaming Platforms: 3 Myths Demystified |access-date=2020-10-28}}</ref>

== See also ==
* [[Alignment level]]
* [[Dialnorm]]
* [[EBU R 128]]
* [[Loudness war]]

== Notes ==
{{Reflist|group="note"}}

== References ==
{{reflist}}

=== Media player features pages ===
{{reflist|group=lower-alpha}}

== External links ==
* [http://wiki.hydrogenaud.io/index.php?title=ReplayGain_specification ReplayGain specification]
* [http://wiki.hydrogenaud.io/index.php?title=Replaygain ReplayGain] at Hydrogenaudio [[wiki]]
* [http://replaygain.hydrogenaud.io/proposal/ Replay Gain – A Proposed Standard], the original proposal, now out of date with respect to current practice
* [http://www.bobulous.org.uk/misc/Replay-Gain-in-Linux.html Replay Gain in Linux] — guide to using graphical and command line ReplayGain tools in Linux.

[[Category:Computer standards]]
[[Category:Digital audio]]