cDSP Loudness

The Loudness and True-Peak Meter helps with the loudness standards compliance and provides inside information for loudness, loudness range and inter-sample peaks.

cDSP Loudness

Introduction to Loudness Standards

ITU BS.1770

The ITU BS.1770 is the most important standard as many other standards are based on it.

The ITU standard concerns Loudness and True-peak Level. The loudness part is based on a Leq measurement (K-weighting), which is a frequency weighting developed by the Communications Research Centre (a federal research institute in Ottawa, Canada).

The True-peak standard was specified by AES SC-02-01.

The standards: ATSC A/85 (US), EBU R128 (Europe), OP-59 (Australia) and TR-B32 (Japan), are based on the ITU standard.

ITU BS.1770 published 2006 (Geneve).

ITU BS.1770-2 published March 2011 (Geneve).

ITU BS.1770-3 published August 2012 (Geneve).

ITU BS.1770-4 published October 2015 (Geneve).

ITU BS.1770-5 published October 2023 (Geneve).

EBU R128

The "P/LOUD" group, part of The European Broadcasting Union (EBU), defined the R128 standard based on ITU BS.1770.

The R128 standard builds on 4 tech documents: EBU Tech 3341, EBU Tech 3342, EBU Tech 3343 and EBU Tech 3344.

The recommended loudness target is -23 LUFS.


ATSC A/85 was specified by The Advanced Television Systems Committee in 2009 and applies to US broadcast digital television. A/85 is rooted in the ITU-R BS.1770 Loudness and True-peak level standard.

A/85 includes information about calibrated monitoring environments and unlike EBU R128, A/85 is only focused on digital television.

Loudness normalisation target of -23 LKFS.

From March 2013, the A/85 recommended practice prescribes ITU BS.1770 for all programming.


TR-B32 is a Japanese standard that builds on ITU BS.1770-2 (gate is employed), however, the target level is -24 LUFS/LKFS as opposed to the -23 LUFS target level of the EBU R128 standard.


Operational practice by FreeTV, Australia. OP-59 is rooted in BS.1770 Loudness and True-peak level.

All short-form programs should be measured using the universal (full mix) method.

Did you know?

As a rule of thumb, a gated measurement of -23 LUFS/LKFS equals an un-gated measurement of -24 LUFS/LKFS!


- Momentary Loudness (400ms window).

- Short-Term Loudness (3000ms window).

- Integrated Loudness (also known as Programme Loudness).

- LRA (Loudness Range).

- True-Peak (also known as inter-sample peaks).


Metering Mode

The Metering Mode, concerns the Loudness Standard used to calculate Loudness.


ITU-R BS.1770-5, EBU R 128 (v5), ATSC A/85:2013, TR-B32, OP-59 and Rel. Gate Off.


The Scale, concerns the Loudness Meters display scale.


Full Scale, -24 Target +9 Scale, -24 Target +18 Scale, -23 Target +9 Scale and -23 Target +18 Scale.

Loudness and LRA - Start, Pause, Reset

We can control the Integrated Loudness and LRA with the "Start", "Pause" and "Reset" buttons.

When active, the "Start" button will tell the meter to begin or resume the metering process, while the "Pause" will pause the current metering calculations.

To clear the meters we press "Reset", which can be done at any point.

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