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Within Wwise, the signal can be measured in different ways. One example is loudness level.
The ITU-R BS.1770 and EBU R128 standards provide recommendations and specifications for measuring the loudness level and loudness range of a given audio program in loudness units (LU or LUFS). It also provides specifications and recommendations for the True Peak level. Wwise implements these specifications and recommendations in the Loudness Meter view and Meter view.
Wwise offers different measurements of the PCM signal:
|
Measurement |
Description |
|---|---|
|
Loudness level |
Provides a measurement of the perceptual loudness of a digital signal. The loudness level can be calculated using different time window sizes. The Loudness level is available in the Loudness Meter view. Units: LUFS or LU |
|
Loudness range |
Provides a statistical analysis of the loudness values over a period of time and a measure of the dynamic range. The Loudness range is available in the Loudness Meter view. Units: LU |
|
True-Peak level |
Provides an estimate of the maximum continuous signal level in the analogue world. This value is useful to ensure that the digital to analogue converter or an external codec is not saturated. The True Peak level is available in the Meter View. Units: dBTP |
|
Peak level |
Provides a measurement of the maximum or minimum values of a PCM signal for a very short period of time. The peak level is shown at the following locations in Wwise:
Units: dBFS |
|
Root mean square (RMS) |
The RMS level is measured with the peak meter values and does an average over a very short period of time. The RMS level is available in the Meter View. Units: dBFS |
The EBU R128 and ITU-R BS.1770 define units for measuring loudness. Loudness is not measured in dBFS.
|
Unit |
Description |
|---|---|
|
Loudness Unit (LU) |
0 LU is equal to the reference level (by default -23 LUFS). Note: The default value of 23 LUFS can be changed in the Loudness Meter settings. |
|
Loudness Unit Full Scale (LUFS) |
0 LUFS/LKFS is equal to 0 dBFs @ 1 kHz according to ITU-R BS.1770-4 and EBU R128 |
|
LKFS |
LKFS is the same as LUFS. ITU-R BS.1770-4 are using the terms LKFS. EBU R128 and using LUFS. |
Loudness can be measured using three different time scopes. In the integrated mode, the loudness level of a game can be determined at a larger scope.
|
Term |
Description |
|---|---|
|
Momentary |
Loudness level calculated using a sliding rectangular time window of length 0.4 seconds. The measurement is not gated. |
|
Short-term |
Loudness level calculated using a sliding rectangular time window of length 3 seconds. The measurement is not gated. |
|
Integrated |
Loudness level calculated using the user capture. The integrated loudness uses gating (all values below -70 LUFS are ignored) and is a long term measurement (an integration over the entire measurement time) based on the momentary loudness. The measurement starts when clicking the Measure button, and stops when clicking it again. Clicking the Reset button restarts the measurement. |
EBU R128 recommends a target level of -23 LUFS for integrated loudness. Selecting -23 LUFS specifically for a game as the target loudness level helps game users obtain a more consistent output level on the output device (television, mobile device etc.) they are using, with other sources. Selecting a specific loudness target level for the whole game also ensures consistent loudness over the different levels or parts of the game. A deviation of ±1.0 LU is acceptable for parts where an exact normalization to the target level of -23.0 LUFS is not practically achievable, due to the dynamic content of games. The loudness levels of a game part are often unpredictable. When a part consists of only background elements (for example, the background music), or where parts are deliberately mixed lower, the loudness level may lie outside the tolerance.
The Sony Worldwide Studios Audio Standards Working Group (ASWG) recommends in ASWG-R001 the following elements:
The Average Loudness Level of audio content within a title developed for home-based platforms should be normalized to a Target Level of -23 LUFS, with a tolerance of ±2 LU, and this tolerance is acceptable considering the non-linear nature of interactive entertainment audio content;
The Average Loudness Level of audio content within a title developed for portable platforms should be normalized to a Target Level of -18 LUFS, with a tolerance of ±2 LU;
Audio content should be measured as a whole, and should not focus on dialogue, sound effects or music specifically;
Audio content should be measured for as long as is practical and for a minimum of 30 minutes, and the measured sections of any title should be a representative cross section of all different parts of any title, in terms of game play;
The recommended maximum LRA is dependent on the genre, the targeted audience, or the environment where the game is intended to be played. The maximum LRA value may also be different for distribution platforms such as the mobile game. Here are a few examples of loudness ranges depending on the listening environment:
|
Environment |
LRA |
|---|---|
|
Home Theater |
20 |
|
Living Room |
18 |
|
Kitchen |
15 |
|
Living Room (Late night) |
9 |
|
Public Transportation (mobile) |
6 |
As a general rule:
A noisy environment requires a lower LRA so that the listener can hear all content correctly
Louder loudspeakers allow a greater LRA
Loudness Range is a measure that also helps to decide if dynamic compression is necessary.
EBU suggests that with the measure of Loudness Range, it is possible to determine appropriate measures for potential dynamic compression of a program to fit within the tolerance window of the audience or distribution platform. In practice, overall low-level compression may lead to satisfactory results and ensure uniform compression of the whole signal range:
a low threshold (< -40 dBFS)
a moderate compression ratio (1:1.2 – 1:1.5)
a long release-time (>1 s)
Again, EBU suggests that depending on the original loudness level, a shift to the target level of -23 LUFS may be performed in parallel through adjusting the make-up gain of the compressor accordingly.
The True Peak measurement detects analog clipping. Even when the peak lies in between samples, so that the distortion that can happen in subsequent Digital-to-Analogue converters, sample rate converters, or commonly used codecs can be predicted and avoided.
The Maximum Permitted True Peak Level recommended in EBU R 128 is -1 dBTP.
To monitor the true peak on the Master Audio Bus:
Open one of four Meter views, using the menu: Views > Meter > Meter - Instance A...D.
Click […] and select the Master Audio Bus.
From the list, select True Peak to monitor the True Peak.
To monitor the integrated loudness on the Master Audio Bus:
Open one of four Loudness Meter views, using menu: Views > Loudness Meter > Loudness Meter - Instance A...D.
Click […] and select the Master Audio Bus.
Click Measure to start calculating the Integrated loudness.
To capture the momentary or short-term loudness level
Open the Loudness Meter view.
In the title bar of the view, select a loudness meter instance from the meter instance selection icon (a letter from A to D).
Select a bus to measure the loudness by clicking the selector [...].
On the Wwise Toolbar, click Capture.
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