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The new specification allows us to accommodate short term dynamic peaks which contribute little to the perception of overall loudness and liberates mixers allowing more open balances with less compression and limiting. By normalising programmes across a broadcast channel’s output according to their loudness levels, this encourages sound engineers to mix with their ears rather than being a slave to the meters.
The introduction of loudness mixing should not be feared by sound mixers. Years of research by the EBU’s P/LOUD committee went into R128 and the target value of -23LUFS for integrated loudness has been carefully chosen so that well mixed programmes to the old PPM standard with a good dynamic range ‘magically’ come out within spec when measured on a loudness meter. This backwards compatibility has been aided by a ‘relative gate’ being incorporated into R128. The gate excludes silences and low level passages from the average or integrated loudness calculation and has the effect of focussing the measurement on the foreground sounds such as speech and featured music which are key to our perception of the overall loudness of the mix.
The new DPP Technical Delivery Standard comes into effect right away and as well as covering the transition to file masters, also covers live programmes and the diminishing number of programmes mastering to HDCAM SR tape. Regardless of how you deliver, the DPP broadcasters will require R128 loudness compliance from now on. The only exceptions to this will be legacy content and programmes that are already in production under the old PPM6 standard which they can continue to use, but may deliver to R128 if they wish.
Commercials are outside the scope of the DPP as they are regulated by the ASA, but it is almost inevitable that their BCAP specification will be revised to incorporate R128 at some point. However promos, sponsorship bumpers and other interstitial material are very much covered by the DPP spec. For short pieces of content like these, the Integrated measurement is less reliable as an indication of the perceived loudness. To counter this, R128 defines a Short Term measurement of a three second floating window and a Momentary measurement of a 400ms window but it stops short of assigning maximum loudness values to them. Different European territories have interpreted this aspect of R128 in varying ways. In France, they specify a maximum Short Term loudness of -20LUFS whilst in the Netherlands they mandate a maximum momentary loudness of -15LUFS.
The Pro Audio Report
This confusion undoubtedly creates more work (and revenue) for those involved in the international distribution of commercials. There is a lot of debate about what is the best approach for short duration material and for now the DPP has declined to set maximum values for the Short Term and Momentary loudness measurements, preferring to wait and see how things progress in the UK and Europe.
It may have been a long time in coming but R128 is now definitely upon us in the UK and there will be very little overlap with the old standard, so what is required to mix to R128? Obviously a good set of ears and a proper acoustic environment are both pre-requisites for loudness mixing. Now more than ever, it’s going to be difficult to mix compliant audio on a set of headphones in the corner of a busy production office!
For those mixing in a live environment such as TV studios and OBs, a straight replacement of PPMs with hardware loudness meters is a viable route. There’s plenty of choice from all the main manufacturers with clear displays for the loudness figures, bar graph true peak meters and some also show loudness history either as a graph or as a radar display. There are also several cost effective loudness meter plug-ins available with similar functionality to their hardware counterparts. The key requirement for a meter is that it meets the EBU Tech 3341 (Aug 2011) standard, then select EBU mode and you’re good to go.
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