EBU recommendation R 128

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Recommendation R 128 of the EBU is a technical set of rules that redefines the sound control of radio and television programs. It has been partially used by public and private television broadcasters in Germany since August 31, 2012; in other countries it was introduced earlier.

prehistory

Up until now, German broadcasting had a level limit that was based exclusively on the peak level. A maximum level of +6  dBu , measured with a quasi-peak level meter , was not allowed to be exceeded. Since the same level does not mean the same level of loudness for the human ear, both the music and advertising industries have made massive use of compressors in the past decades to ensure that pieces of music and commercials get louder and louder without exceeding the peak level . In the professional world this phenomenon is called " Loudness War " ("Loudness War"). The resulting differences in the perceived loudness are a frequent cause of complaints from viewers and listeners to the technically responsible at the radio stations. Therefore, a solution was sought that enables the loudness of different programs and program contents to be adjusted.

EBU working group "P / LOUD"

As part of an international working group, engineers and sound engineers from various broadcasting stations and broadcasting institutes initially developed evaluation and measurement methods in order to enable the industry to design appropriate measuring instruments and offer them on the market. At the same time, an information document was drawn up to enable broadcasters and external program producers to convert their sound processing to the new recommendation. Another reference document deals with the procedures in the area of ​​the actual broadcast of the finished program, i.e. the signal distribution.

The recommendation "R 128"

With the EBU recommendation "R 128", new units of measurement are introduced to characterize an audio signal:

  • LUFS , "Loudness Units relative to Full Scale", ie "Loudness units relative to the digital standard level (0 dBFS)".
  • LU , Loudness Units, the relative value of LUFS. 1 LU corresponds to 1 dB.
  • LRA “Loudness Range”, a statistically determined value that describes the dynamics of a program section.
  • dBTP , "dB relative to true peak", a value for the correctly measured digital modulation, which takes peaks between samples into account.

It is stipulated that a target level of −23 LUFS ± 1 LU, measured over the entirety of the spot, contribution or broadcast, must be adhered to. In addition, a digital peak level of −1 dBTP must not be exceeded.

By implementing this recommendation, which leads to a “loudness normalization”, the loudness impression perceived by the listener should remain almost the same over the entire course of the program and there should be no constant readjustment of the volume on the receiving device when switching between different stations. The level can still fluctuate more, so the dynamics of the program can be increased and made more interesting.

In practice, the average loudness depends on the spoken, ostensible language, because experience has shown that most listeners adjust their listening volume accordingly.

Technical implementation

The loudness is measured using the defined EBU mode measurement algorithms (digital plug-ins or physical outboard devices). Real-time measurement algorithms can be used to measure 'instantaneous' loudness values ​​("M" for "Momentary", averaged over the last 400 milliseconds) as well as briefly averaged values ​​("S" for "Short Term" averaged over the last 3 seconds) .

On the other hand, the integrated average loudness of the entire audio section to be normalized (commercial, feature, feature film ...) is carried out either by a real-time scan using a start-stop button when listening with a subsequently determined value output (time-consuming for large to measuring time periods), or the integrated overall loudness is quickly carried out by an 'offline' measurement (faster than real time, without eavesdropping) (practical, the longer the time period to be measured).

A noise gate function is used to determine the overall loudness value , which is used to exclude silence and 'background noise' (below a prescribed threshold value) from the measurement, as these would otherwise distort the measured value. So only 'main' loudnesses (above this threshold) are included in the measurement.

Measuring instruments are available on the market for installation, as well as software that enables both the measurement and the normalization of entire audio files.

Existing productions must be normalized to −23 LUFS, which usually means that the overall level has to be reduced, since earlier productions were controlled significantly higher than −23 LUFS.

Since the implementation of the EBU recommendation "R 128" is not binding, individual television stations have already started to set their own additional conditions for the production of the program. For example, the ORF has a limit of -3 dbTP for data-reduced formats, arte issues guide values ​​for the LRA and various broadcasters require maximum M and S loudness values ​​for short programs such as commercials in addition to the average loudness of -23 LUFS.

outlook

In principle, the recommendation is also applicable to radio programs. So far, no binding introduction date has emerged there. In the meantime, loudness-related control is also being gradually introduced on the radio. For example, the BR changed its radio programs at the end of 2015. The introduction on the Internet is difficult: While the television stations have agreed on the new recommendation on all distribution channels, there will also be a large number of different providers of video and audio material on the Internet in the future who normalize their sound level to 0  dBFS , so that the Internet will continue to make significant leaps in loudness. There will probably only be a change here once the implementation of the R 128 on television has proven itself and is accepted.

See also

Web links

Individual evidence

  1. ↑ The EBU recommendation "R 128" in German (PDF; 401 kB)
  2. ↑ Document of the EBU on loudness measurement (PDF; 1.1 MB)
  3. ↑ EBU document on the practical application of the recommendation (PDF; 4.9 MB)
  4. ↑ Document of the EBU on the digital distribution of loudness-normalized programs (PDF; 1.3 MB)
  5. ↑ Document of the EBU on the Loudness Range (PDF; 1.1 MB)
  6. ↑ BR optimizes sound by modulating according to loudness (press release of July 10, 2015)