Standardising loudness - PSNEurope

Standardising loudness

For years there was no official standard to combat the problem of broadcast loudness. Now there are several and while, as Kevin Hilton reports, they are all similar in technology and intent, there are enough differences to cause uncertainty.
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For years there was no official standard to combat the problem of broadcast loudness. Now there are several and while, as Kevin Hilton reports, they are all similar in technology and intent, there are enough differences to cause uncertainty.

The majority of laws and standards are created with good intentions. But as more people get involved with them there is the danger that the whole process will drag on or the original aim will be obscured. That seems to be the dilemma facing everyone concerned with broadcast loudness.

The first official guidelines began to appear five years ago. These, and subsequent recommendations, were based on the ITU-R BS (Broadcast Service) series documents 1770 (Algorithms to measure audio programme loudness and true-peak audio level) and 1771 (Requirements for loudness and true-peak indicating meters), published in 2006-07.

In principle BS 1770 superseded individual attempts to deal with loudness, including the metering systems produced by Chromatec and Dorrough. Manufacturers including DK Technologies, TC Electronic and RTW introduced a new generation of products based on the ITU algorithm and guidelines. But there were concerns that while 1770 was a start, it did not go far enough. Specifically there was no target level or indication where the common loudness level should be.

Consequently the EBU established the PLOUD working group to fill in the gaps. Its recommendations were published at IBC 2010; the core is R128, which specifies loudness normalisation and permitted maximum level of audio signals.

While many broadcasters, including NDR in Germany and the UK Digital Production Partnership (DPP), a joint venture between the BBC, ITV and Channel 4 to define standards for the interchange of HD and SD broadcast material, have opted for R128, a great many organisations are already adhering to 1770.

Another omission from the ITU standard was a gating feature to increase signal bandwidth. PLOUD built this into R128, setting the range at -8dB. At the end of February the ITU introduced a revised version of 1770, which incorporates a relative gate, set at -10dB.

Florian Camerer, the ORF senior sound engineer who chaired PLOUD, says that in light of 1770-2 the EBU will update its documents, in particular R128 and Tech Docs 3341 and 3342 to reflect the -10 relative gating. Revisions of the EBU guidelines are expected by the end of this month because, Camerer says, there only should be only one gating threshold and method.

Manufacturers have built both the original 1770 and R128 into their metering and monitoring products. RTW updated its ranges, including the TouchMonitor and SurroundMonitor series, to R128 earlier this year.

Technical director Mike Kahsnitz says the company is now fully R128 compliant for Europe but observes that many European countries, and Germany specifically, did not want to jump on the -23LUFS laid down in the recommendations.

“Nobody wants to be first,” he comments, “so we offer the chance for people to change as they go along. We’ve also been waiting to hear the outcome of ITU 1770-2. There is now the gate on both recommendations and even though the range is -8dB on one and -10dB on the other, that’s not a big problem. In the future 1770-2 will be implemented into our products and that won’t be a major change.”

As John Emmett, technical director of Broadcast Project Research and designer of the Chromatec Loudness algorithm, observes, there’s no point in fighting over a couple of dB but this particular point does highlight that despite best efforts, there is still no single way to deal with loudness. “Each country seems to have its own agenda,” says Emmett.

Italy was among the first countries in Europe to lay down guidelines; the Authority for Communications Guarantees (AGCOM) introduced rules during 2006 stipulating a difference of only 0.6dB between advertisements, promos, idents and the main shows. In the UK the Broadcast Committee on Advertising Practice (BCAP) brought out guidelines on audio levels of television advertisements during July 2008. As with AGCOM, the BCAP rules are based on 1770 and will not be updated to R128.

The government in the Netherlands is introducing regulations based on R128. From 1 January 2012 broadcasters will only be able to accept material for transmission and live broadcast that complies with the EBU standard.

Dutch manufacturer Axon has built R128 into its Synapse 3 range of modular signal processors to give loudness control. Peter Schut, the company’s chief technical officer, says that complying with R128 is a “no-brainer” for all modern TV broadcasters. He foresees a time when R128 will be embedded into the day-to-day workflow of production, mastering, postproduction, contribution and transmission of audio.

In France documents have been drawn up for a law that will require “shortform content”, including commercials, to be normalised starting from 1 January 2012. Public broadcasters in Germany, Austria and Switzerland have a target of January next year to begin complying with the -23 LUFS target.

Inconsistent approach

While this shows a commitment, albeit a belated one, by governments and regulatory authorities to tackle loudness, there are still inconsistencies in approach. Tim Carroll, chief executive of Linear Acoustic, observes that the US CALM (Commercial Advertisement Loudness Mitigation) Act, based on the ATSC (Advanced Television Systems Committee) A/85 standard, which used 1770 at its foundation, identifies commercials as the root of the problem. “But in reality it’s anything that pisses off the viewer,” he says. Carroll continues that while 1770 and R128 specify parameters within which ads are theoretically “legal”, there can still be problems if other material deviates from the norm. “I’ve recorded blocks of programming and commercials that were-24 as they should be,” he explains. “But then a programme comes in at -18 and you’ve got a substantial difference in level. The people behind the commercial can say “it’s -24” but to the viewer there’s still a problem.”

Carroll takes the view that government and regulators can legislate and specify technology to deal with loudness as much as they want but it does not necessarily cure the problem. “It’s thinking too much about it,” he says. “A/85 will happen in the US but it can be interpreted in so many different ways. If you want a meter that to show -24 you can buy one from Maplin. There’s been all this work on the numbers but none of it takes quality into account.”

Camerer’s aim in drawing up R128 was to liberate mixers from being tied to watching a meter and allow them to mix as their ears tell them. Richard Burden began working as a broadcast engineer in the US during the 1950s and has been an “associate member” of the Dorrough team for 25 years. He agrees with the ideal of mixers relying on their own hearing and judgement but says there is a need for “something to get where you need to be”.

Dorrough’s meters incorporate 1770 and R128 but the company has not completely moved away from the algorithm that was the basis of its first loudness products at the end of the 1990s. Burden explains that the original Dorrough system remains available because there are still “thousands of meters out there using that characteristic”. He adds that having the algorithm on the same meter as 1770 creates a common reference point so someone used to the old system will see the measure moving as he or she would expect.

For the same reasons Chromatec is reintroducing its own Loudness algorithm on the Multi-viewer range as a firmware update. Managing director Michael Stevens says he was “constantly bombarded with requests” for the Chromatec Loudness feature and eventually decided to bring it back.

Multi-viewer is now based on the original 1770 but, says Stevens, users will be able to select either that or Chromatec Loudness. Stevens observes there are “slight differences and variations” between the different international recommendations and so the hope in the market must have been for a common standard. “But, as usual, there has been diversification,” he says.

Chromatec takes the approach, Stevens says, of “going with the flow” and will introduce R128- and 1770-2-compliant products in the future. Following the trends and using other companies’ technology, or full collaboration, is a new approach in loudness and one that could bring about greater commonality between formats and systems.

Axon is using Linear Acoustic’s algorithm in the Synapse range, while at NAB Dolby Laboratories announced that it plans to allow other manufacturers to use its dialogue gating technology free of charge and will license its range of loudness metering and correction technologies. Dolby also introduced the Media Emulator software package, which is designed to produce an optimised soundtrack delivery stream, meeting current broadcast specs and allowing operators to monitor loudness levels.

During June TC Electronic announced that it had incorporated 1770-2 into loudness products, including System 6000 MkII (v.5.11), DB4 (v.3.20) and TC TouchMonitor TM7 & TM9 (v. 1.14) products.

TC Electronic technology forms part of R128 and is now used in 1770-2. Head of product management for broadcast equipment, Thomas Lund, says that although 1770-2 does not yet have all the tools offered by R128, it can be used in conjunction with the EBU standard installed on TC equipment to offer a full range of features. “The ITU has been moving slower,” he says, “but it is looking at some important tools, including programme loudness measurements.”

A loudness meter is a practical tool. The creative tool in audio mixing is the sound desk and manufacturers in this field have been looking at how to bring the two sides closer together. Lawo now has loudness metering on all its mc2 series consoles. Jeffrey Stroessner, product specialist for the mc2 range, says the company wanted to not only comply with the standards and implement loudness metering “as it needs to be” but also considered how it could be implemented in a mixing console. “We finally decided to implement loudness metering in every channel,” he explains. “That gives the operator a subjective meter beside an objective technical peak meter. We call this Combi Meter and it gives the possibility to compare every signal in loudness in the console.”

There is general agreement among most manufacturers and broadcast engineers that loudness measurement should be used from the start of the production chain to get material right before transmission. Sometimes this is not always possible and with the growing use of automation and file-based systems, there is concern that in some cases the control of loudness will be left to a slightly more sophisticated form of limiter on the output.

Eyeheight produces the KARMAudioAU plug-ins for Final Cut Pro and Avid, which work with raw ITU 1770 and EBU R128 processed signals to hit target loudness and peak programme levels. These systems are designed for fast turnaround work where there is no time for a full dub and craft loudness mixing. Eyeheight also produces transmission output legalisers that will limit any discrepancies or deviations from specified loudness parameters.

Eyeheight’s research and development director, Simon Pegg, describes the limiting as “very benign”. He adds that it would only kick in on very loud signals – such as gunshots – in material that had already been mixed through loudness meters. Pegg says the combination of craft mixing and automated levelling, with limiting as the final fallback, should go some way to helping combat loudness.

Wherever the loudness control is done, there is still the fundamental problem of different broadcasters and authorities in different countries having differing views on what needs to be done and for what material. Richard Kelley, director of sales and marketing at DK Technologies, observes that people might just stick with what they’re already using. “The UK has gone with the [original] ITU spec so are facilities going to change?” he asks.

But Kelley identifies an even more basic problem in the range of views, standards and procedures for loudness today: “What is getting to most users and manufacturers is that we don’t get a chance to stand still. I talk to the people who are affected by all this and they worry that if we don’t stop we’ll just carry on playing with the spec. Eventually the industry will say ‘Enough is enough’. Before we get to that point we need to be able to look at everything and interpret it into how we work.”



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