EBU R 128

Last updated

EBU R 128
Loudness normalisation and permitted maximum level of audio signals
StatusPublished
Year started2012
First published2010
Latest version4.0
August 2020
Organization European Broadcasting Union
Related standardsITU-R BS.1770
Website https://tech.ebu.ch/publications/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. [1] It was first issued by the European Broadcasting Union in August 2010 and most recently revised in August 2020. [2]

Contents

R 128 employs an international standard for measuring audio loudness, stated in the ITU-R BS.1770 recommendation and using the loudness measures LU (loudness units) and LUFS (loudness units referenced to full scale), specifically created with this purpose. [3] The EBU Tech 3341 document further clarified loudness metering implementation and practices in 2016. [4]

Premise

Before the adoption of R 128, normalisation was based on the peak level of audio signals, which led to considerable loudness discrepancies between programmes and between broadcast channels. [1] The same peak level does not necessarily produce the same loudness, because the use of dynamic range compression and limiting can increase the average level of the programme without increasing its peak level. Starting from the early 1990s through the early 2010s, both the music and the advertising industries urged the continuation of this practice to ensure that music and advertising spots became louder without exceeding the maximum permitted peak level. This phenomenon is known as the loudness war.

The resulting inconsistencies and changes in loudness, especially between programmes and commercials, became a frequent cause of complaints from viewers and listeners. To help address these problems, the International Telecommunication Union (ITU) developed new algorithms to measure audio programme loudness in a manner similar to how the human ear perceives sounds and studied new methods to measure loudness over a long-term timeframe. This would allow normalising the loudness of different programs and programme contents appropriately. [1]

Development

To find practical solutions for the switch from peak normalisation to loudness normalisation, the EBU Production Management Committee formed an international working group comprising sound engineers from various radio stations and broadcasting institutes. Its name, PLoud, derived from a combination of the words production and loudness. [5]

The group first developed evaluation and measurement methods to guide the development of appropriate measurement instruments in the industry. [4] It drafted a technical document to enable broadcasters and programme producers to change their sound processing to the new recommendation, [6] while another technical document dealt with the procedures to follow in the signal distribution. [7]

Specification

Definitions

To characterise the level and the dynamic range of an audio signal, R 128 introduced new units of measurement:

UnitDefinitionDescriptionExamples and implementation
LK K-weighted loudness levelLoudness level measured with K frequency weighting.R 128 target level is: LK = −23 LUFS
LUFS Loudness Units referenced to full scale Loudness measurement unit on an absolute scale, K-weighted, [3] relative to a digital scale (the upper limit of which is 0 dBFS). Equivalent with LKFS, used in ITU-R BS.1770.
LULoudness UnitRelative loudness measurement. 1 LU corresponds to the relative measurement of 1 dB on a digital scale. LU can also express the difference in level from the target level. [5] In a loudness meter implementing EBU Mode: Reference level = −23 LUFS = 0 LU
A programme with an integrated loudness of −26 LUFS measures −3 LU in EBU Mode (i.e. is 3 LU quieter than the target level).
LRALoudness Range [8] A statistically determined value that describes the loudness variation (dynamics) of a programme.R 128 does not prescribe a maximum loudness range. LRA could be limited arbitrarily during production for aesthetic purposes (depending on style or genre) or practical purposes (depending on the environment where the programme is intended to be played back: for example, a home theatre, a mobile device or a cinema).
TPTrue PeakReconstruction of the inter-sample peak level of the signal (the peak level generated between two samples), calculated by oversampling. [9] The maximum true peak level permitted by R 128 in production is −1 dBTP.
dBTPTrue Peak level referenced to full scaleLevel in of the audio signal that takes inter-sample peaks into account, measured in decibels relative to full scale.

Normalisation

R 128 recommends normalising audio at the target level of −23 LUFS. This measurement is the integrated loudness calculated over the whole duration of the programme and in the entirety of its contents (i.e. without emphasising specific foreground elements, such as voice). [1] A deviation of ±0.5 LU is permitted. When practical limitations prevent achieving this accuracy (specifically, less predictable materials such as live mixed programmes), a wider tolerance of ±1 LU is permitted. Furthermore, the whole programme must not exceed the peak level of −1 dBTP. [1]

To ensure loudness meters developed by different manufacturers provide the same reading, EBU Tech 3341 defines EBU Mode which describes how to perform the measurement using the ITU-R BS.1770 recommendation. [4]

Metering

EBU Mode specifies three distinct methods which analyse loudness over three different timeframes:

Real-time meters must provide an update rate of at least 10 Hz for short-term meters and of at least 1 Hz for integrated loudness meters.

To prevent silent passages of a programme from misrepresenting the overall loudness measurement, integrated loudness is measured through two gating functions: absolute and relative. The detection gate, specified in ITU-R BS.1770-4, considers silence the portions of audio in which the signal falls below the absolute threshold of −70 LUFS; similarly, the relative gate also drops incoming loudness data if the average level falls 10 LU below the current integrated loudness value. [9] Measurement is not gated in momentary and short-term loudness metering. [4]

Implementation

Screenshot of ebur128, a part of ebumeter program to measure loudness normalisation according to EBU R 128 EBU R 128 measurement on Linux screenshot.png
Screenshot of ebur128, a part of ebumeter program to measure loudness normalisation according to EBU R 128

EBU R 128 and EBU Mode have been implemented by several software developers, audio technology companies and content distributors, including Adobe, Apple, Dolby, iZotope, Magix, PreSonus, Sonible, [10] Sony, Steinberg, TC Electronic, Toyo, Orban and Waves. [11]

Real-time metering plug-ins aid engineers in their mixing decisions and in delivering R 128-compliant programmes, while broadcasters and content distributors can check and normalise whole programmes by performing a faster-than-real-time analysis; programmes produced before the recommendation are likely to be lowered in volume to match the target level.

Ebumeter is open source software that provides level metering according to EBU R 128 [12] and libebur128 [13] an open source library that implements it.

Adoption and aftermath

The recommendation encourages the use of a wider dynamic range in production but does not restrict the use of dynamic range compression. In essence, it ties the use of compression to artistic and aesthetic decisions, rather than the necessity of obtaining a louder mix. [5] With the adoption of normalisation by broadcasters since the introduction of EBU R 128, reducing dynamic range in production does not render the program louder in broadcast. [14] Widespread adoption of ITU-R BS.1770 and EBU R 128, combined with the prevailing of streaming over physical media distribution in the 2010s, arguably put an end to the loudness war. [9]

Starting in 2012, European countries integrated EBU R 128 to their audiovisual legislation and television stations in Europe adopted it on all distribution channels. [15] Sky UK adopted R 128 in 2013. [16]

R 128 is applicable also to radio programmes and is gradually being introduced in European radio broadcasts: for example, German public broadcaster BR changed its radio programmes at the end of 2015. [17]

Since R 128 implementation is not binding,[ further explanation needed ] some television stations have imposed additional conditions on programme production. For example, Austrian public broadcaster ORF has a limit of −3 dBTP for data-reduced formats; Franco-German TV network ARTE has published guidelines for LRA; various broadcasters impose maximum momentary and short-term loudness values for short reports, such as commercials.

Through the 2010s, Internet streaming services have implemented loudness-based normalisation, even though each platform uses different methods and target levels: for example, YouTube and Tidal use downward normalisation only (turn down louder content to match the target level, but do not turn up quieter content). [18] Spotify uses ITU-R BS.1770 to measure loudness and normalizes to a selectable target level of −11, −14 or −19 LUFS. [19] Apple Music activates loudness normalisation when the iTunes Sound Check option is enabled.

Target levels (or estimated equivalent level) adopted by streaming services
Target levelPlatform
−14 LUFS Tidal, Amazon Music, [18] YouTube, [18] Spotify [19]
−16 LUFS Apple Music [20]
−18 LUFS Qobuz [ citation needed ]

Related Research Articles

<span class="mw-page-title-main">Weighting filter</span>

A weighting filter is used to emphasize or suppress some aspects of a phenomenon compared to others, for measurement or other purposes.

<span class="mw-page-title-main">Dynamic range compression</span> Audio signal processing operation

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 commonly used in sound recording and reproduction, broadcasting, live sound reinforcement and some instrument amplifiers.

<span class="mw-page-title-main">Loudness</span> Subjective perception of sound pressure

In acoustics, loudness is the subjective perception of sound pressure. More formally, it is defined as the "attribute of auditory sensation in terms of which sounds can be ordered on a scale extending from quiet to loud". The relation of physical attributes of sound to perceived loudness consists of physical, physiological and psychological components. The study of apparent loudness is included in the topic of psychoacoustics and employs methods of psychophysics.

ReplayGain is a proposed technical standard published by David Robinson in 2001 to measure and normalize the perceived loudness of audio in computer audio formats such as MP3 and Ogg Vorbis. 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 at different loudness levels.

<span class="mw-page-title-main">VU meter</span> Audio signal level measurement device

A volume unit (VU) meter or standard volume indicator (SVI) is a device displaying a representation of the signal level in audio equipment.

Audio normalization is the application of a constant amount of gain to an audio recording to bring the amplitude to a target level. Because the same amount of gain is applied across the entire recording, the signal-to-noise ratio and relative dynamics are unchanged. Normalization is one of the functions commonly provided by a digital audio workstation.

In digital and analog audio, headroom refers to the amount by which the signal-handling capabilities of an audio system can exceed a designated nominal level. Headroom can be thought of as a safety zone allowing transient audio peaks to exceed the nominal level without damaging the system or the audio signal, e.g., via clipping. Standards bodies differ in their recommendations for nominal level and headroom.

dBFS Unit of measurement for amplitude levels in digital systems

Decibels relative to full scale is a unit of measurement for amplitude levels in digital systems, such as pulse-code modulation (PCM), which have a defined maximum peak level. The unit is similar to the units dBov and decibels relative to overload (dBO).

<span class="mw-page-title-main">Peak programme meter</span> A quasi-peak audio level meter originally developed in the 1930s

A peak programme meter (PPM) is an instrument used in professional audio that indicates the level of an audio signal.

Broadcast Wave Format (BWF) is an extension of the popular Microsoft WAV audio format and is the recording format of most file-based non-linear digital recorders used for motion picture, radio and television production. It was first specified by the European Broadcasting Union in 1997, and updated in 2001 and 2003. It has been accepted as the ITU recommendation ITU-R BS.1352-3, Annex 1.

<span class="mw-page-title-main">ITU-R 468 noise weighting</span> Noise measurement standard

ITU-R 468 is a standard relating to noise measurement, widely used when measuring noise in audio systems. The standard, now referred to as ITU-R BS.468-4, defines a weighting filter curve, together with a quasi-peak rectifier having special characteristics as defined by specified tone-burst tests. It is currently maintained by the International Telecommunication Union who took it over from the CCIR.

In acoustics, noise measurement can be for the purpose of measuring environmental noise or measuring noise in the workplace. Applications include monitoring of construction sites, aircraft noise, road traffic noise, entertainment venues and neighborhood noise. One of the definitions of noise covers all "unwanted sounds". When sound levels reach a high enough intensity, the sound, whether it is wanted or unwanted, may be damaging to hearing. Environmental noise monitoring is the measurement of noise in an outdoor environment caused by transport, industry and recreational activities. The laws and limits governing environmental noise monitoring differ from country to country.

<span class="mw-page-title-main">Loudness war</span> Increasing levels in recorded music

The loudness war is a trend of increasing audio levels in recorded music, which reduces audio fidelity and—according to many critics—listener enjoyment. Increasing loudness was first reported as early as the 1940s, with respect to mastering practices for 7-inch singles. The maximum peak level of analog recordings such as these is limited by varying specifications of electronic equipment along the chain from source to listener, including vinyl and Compact Cassette players. The issue garnered renewed attention starting in the 1990s with the introduction of digital signal processing capable of producing further loudness increases.

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 subjectively valid measure of loudness that many would argue is needed to optimise the listening experience when changing channels or swapping disks.

The alignment level in an audio signal chain or on an audio recording is a defined anchor point that represents a reasonable or typical level.

RF64 is a BWF-compatible multichannel audio file format enabling file sizes to exceed 4 GiB. It has been specified by the European Broadcasting Union. It has been accepted as the ITU recommendation ITU-R BS.2088.

Dialnorm is the metadata parameter that controls playback gain within the Dolby Laboratories Dolby Digital (AC-3) audio compression system. Dialnorm stands for dialog normalization. Dialnorm is an integer value with range 1 to 31 corresponding to a playback gain of -30 to 0 dB (unity) respectively. Higher values afford more headroom and are appropriate for dynamic material such as an action film.

<span class="mw-page-title-main">A-weighting</span> Frequency response curves used in sound pressure level measurement

A-weighting is a form of frequency weighting and the most commonly used of a family of curves defined in the International standard IEC 61672:2003 and various national standards relating to the measurement of sound pressure level. A-weighting is applied to instrument-measured sound levels in an effort to account for the relative loudness perceived by the human ear, as the ear is less sensitive to low audio frequencies. It is employed by arithmetically adding a table of values, listed by octave or third-octave bands, to the measured sound pressure levels in dB. The resulting octave band measurements are usually added to provide a single A-weighted value describing the sound; the units are written as dB(A). Other weighting sets of values – B, C, D and now Z – are discussed below.

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.

Linear Acoustic is an American company based in Lancaster, Pennsylvania that develops technology and manufacturers equipment used by television stations, cable television and satellite television services providers, post-production facilities and other content services providers to control, measure, manage and monitor multi-channel digital audio. The company has been especially active in areas related to automated upmixing and downmixing of multichannel broadcast audio, and with issues related to relative loudness of broadcast audio.

References

  1. 1 2 3 4 5 "R 128 – Loudness normalisation and permitted maximum level of audio signals" (PDF). tech.ebu.ch. Geneva: European Broadcasting Union. June 2014. Retrieved 31 March 2020.
  2. ↑ "Change log R 128 v3.0" (PDF). tech.ebu.ch. 31 May 2016. Retrieved 5 April 2020.
  3. 1 2 "Recommendation ITU-R BS.1770-2 – Algorithms to measure audio programme loudness and true-peak audio level" (PDF). International Telecommunication Union. March 2011. Retrieved 31 March 2020.
  4. 1 2 3 4 "Tech 3341 – Loudness Metering: 'EBU Mode' metering to supplement Loudness normalisation" (PDF). tech.ebu.ch. Geneva: European Broadcasting Union. January 2016. Retrieved 4 April 2020.
  5. 1 2 3 "Ploud (Loudness) – FAQ". tech.ebu.ch. 18 December 2019. Retrieved 8 April 2020.
  6. ↑ "Tech 3343 – Guidelines for production of programmes in accordance with EBU R 128" (PDF). tech.ebu.ch. Geneva: European Broadcasting Union. January 2016. Retrieved 4 April 2020.
  7. ↑ "Tech 3344 – Guidelines for distribution and reproduction in accordance with EBU R 128" (PDF). tech.ebu.ch. Geneva: European Broadcasting Union. July 2016. Retrieved 4 April 2020.
  8. ↑ "Tech 3342 – Loudness Range: measure to supplement loudness normalisation" (PDF). tech.ebu.ch. Geneva: European Broadcasting Union. January 2016. Retrieved 4 April 2020.
  9. 1 2 3 Robjohns, Hugh (February 2014). "The end of the loudness war?". Sound on Sound . Retrieved 8 April 2020.
  10. ↑ "Sonible true:level manual" (PDF). sonible.com. March 2023. Retrieved 7 April 2024.
  11. ↑ "Ploud (Loudness) – Implementations". tech.ebu.ch. 18 December 2019. Retrieved 8 April 2020.
  12. ↑ "Ebumeter - Quick guide". kokkinizita.linuxaudio.org. Retrieved 29 December 2021.
  13. ↑ "libebur128" . Retrieved 12 September 2024.
  14. ↑ Schorah, Jon; Inglis, Sam (June 2017). "Mastering for streaming services". Sound on Sound . Retrieved 8 April 2020.
  15. ↑ "Loudness: France chooses EBU R128 to bolster audio laws". European Broadcasting Union . 25 October 2011. Retrieved 8 April 2020.
  16. ↑ Davies, David (9 December 2013). "Sky confirms formal adoption of R128 loudness specification". SVG Europe. Retrieved 8 April 2020.
  17. ↑ Rundfunk, Bayerischer (10 July 2015). "Angenehmer hören: BR optimiert Klang durch Aussteuerung nach Lautheit". BR.de (in German).
  18. 1 2 3 Shepherd, Ian (18 September 2019). "YouTube changes loudness reference to –14 LUFS". meterplugs.com. Retrieved 8 April 2020.
  19. 1 2 "Mastering & loudness – FAQ – Spotify for Artists". artists.spotify.com. Retrieved 11 May 2021.
  20. ↑ "Apple Switches to LUFS, Enables Sound Check by Default". meterplugs.com. Retrieved 8 May 2022.
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