EBU loudness specification changes

The EBU updates on loudness take into account the experience gained over the past five years of loudness measurement and normalisation.

Here is a recap of the key specifications and the main changes.

Short content = short measurement

EBU R128 s1 – the supplement dealing with short-form content, such as commercials – has been simplified. In the previous version, users could use either a Maximum Momentary or a Maximum Short-term Loudness measurement as a parameter to prevent overly dynamic mixes. In the new version, only the short- term measurement is specified. The EBU anticipates that reducing the options will help simplify content exchange and reduce costs in daily operations.

More test signals for EBU Mode

The ‘EBU Mode’ Loudness Metering specification (EBU Tech 3341) has been updated with new minimum compliance requirements and various clarifications; one of which is the need for meters to signal that the Loudness Range calculation is not stable within the first 60 seconds of a programme.

The complementary EBU Loudness Test Set has been extended with many new test signals, which help implementers to check if equipment measures short-term and Momentary Loudness, as well as True Peak levels correctly.

More accurate loudness range

The Loudness Range (LRA) specification (EBU Tech 
3342) now specifies that the minimum block overlap between consecutive analysis windows is 2.9 seconds (i.e. ³10Hz sampling of the loudness level).

This new value fits well with the requirements for the Integrated Loudness and short-term measurements. LRA can be used as an indicator for potential dynamics reduction processes in a signal chain, performed on purpose or accidentally.

LRA is useful as a mixing tool, but it should not be a brick-wall parameter for delivery specifications of programmes. It is important to understand that no single maximum valueof LRA can be specified for all broadcasters and all programmes.

New studio listening level

Probably the most practical of all of the EBU Loudness publications are the updated ‘Production Guidelines’ (EBU Tech 3343). If you are new to audio/loudness, EBU Tech 3343 is the specification to read first. The advice for mixing and normalising different genres has been expanded, especially for sports, shows, movies and commercials.

Another important change is the new Reference Listening Level for studios. To help production staff to set up rooms correctly when normalising to the EBU recommended Loudness Level of -23 LUFS, the EBU now specifies that each loudspeaker should be adjusted to 73dBC SPL, respectively, when playing back a reference monophonic noise signal (500-2000Hz @ -23 LUFS).

The signal is appropriate for average size mixing rooms ranging from 125 to 250 cubic metres. This method is completely independent of the actual format and thus the number of loudspeakers. The proceeding is the same for stereo, surround sound or one of the currently discussed immersive systems like 9.1 Auro 3D.

Shorter distribution guide

In 2016, the EBU also published a new version of its Loudness Guidelines for distribution and reproduction (EBU Tech 3344). The new guidelines are easier to read, as they have been halved in size (-3dB in engineers speak), but without losing any of their power.

The main goal of EBU Tech 3344 is to make sure that the quality of the audio provided by broadcasters is kept all along the chain. In today’s multimedia world, programme audio can travel many paths and be subject to many changes along the way. EBU Tech 3344, arguably, is the only document in the industry that provides a complete overview of how audio signals flow from studio via distributors to consumer devices such as IRDs, televisions, radios, and media players.

It covers audio levels in anything from legacy SCART outputs to the latest AC-4 and MPEG-H compression systems and includes checklists to help ensure compliance.

Important changes include the addition of AC-4 and MPEG-H, guidance on DRC for various codecs, including ‘presentation mode’ for MPEG-4 AAC & HE-AAC, and details on how to handle mono audio presented on stereo and multi-channel outputs.

On the radio distribution side, updated FM alignment guarantees a better correspondence with networks based on 0dBr MPX power, and automatic loudness matching in combined FM radio and DAB/ DAB+ receivers provides for a better user experience when switching between analogue and digital radio reception. EBU Tech 3344 Version 2.0 also includes advice on loudness normalisation in mobile devices such as personal music players.

The EBU’s loudness work continues, with special attention now being paid to streaming audio services.

For more information, see: https://tech.ebu.ch/loudness

This article was first published at IBC2016.