Navigating the Complex Terrain of Loudness Compliance:

Friday, March 29, 2013

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Regulatory bodies throughout Europe are in various stages of enacting loudness legislation based on the PLOUD R128 recommendations. In Italy, for instance, AGCOM regulates loudness based on the customer experience post-set-top-box, after all audio processing has taken place.

Gary Learner, chief technology officer at Volicon believes that answer to many loudness compliance issues may be found in new capabilities with video logging and monitoring systems.

It’s something we can all relate to. We’re sitting in our living rooms, watching our favourite program, when suddenly a commercial that is several decibels louder makes us jump out of our seats. From the viewer’s perspective, commercial loudness has been a major annoyance for years.  But recently it’s taken on even greater significance for broadcasters and video service providers in countries throughout the world, as their governments continue to enact legislation regulating content loudness. 

 

Regulatory bodies worldwide such as the EBU are drawing on loudness recommendations and technical specifications such as ITU BS 1770 to formalize requirements enforceable by fines and other punitive measures. But loudness is an issue that pre-dates recent legislation, and audio inconsistencies in advertising are a common theme of viewer complaints. With viewer loyalty on the line, broadcasters and video service providers have added loudness to the list of critical factors that need to be closely monitored, corrected, and managed. 
In this article, we will provide some background on loudness regulation in Europe and describe the key requirements for an effective loudness monitoring, logging, and troubleshooting solution.

Defining loudness
The emergence of digital sound has brought about a fundamental shift in the way broadcasters approach loudness measurement, since digital audio affords a much greater dynamic range than the analog sound world of yesteryear. Peak metering techniques were previously adequate for leveling analog audio content, since the dynamic range was limited at the upper end by modulation limits and adjacent channels, and at the lower end by the noise floor. Since all program elements were perceived at similar levels, consumers didn’t feel the need to adjust the volume for commercials.
 
However, improved transmission methods for digital content have created the opportunity to super-elevate the dynamic range to create more of a theater-like experience for viewers. Advertisers have jumped on this, recognizing that they can push their content into the headroom portion of the audio to make commercials louder and get viewers’ attention. Operators may still be able to use peak metering to level the audio according to peaks, but this does not prevent the perceived level of commercials from being higher and thus affecting viewers’ quality of experience.

With these factors in mind, global industry groups such as ITU and ATSC have focused on creating new standards for loudness that`preserve the user experience, while maintaining content flexibility – a tall order given the highly subjective nature of loudness, experienced in different ways by different viewers. `The ITU’s attempt to objectify the subjective is BS 1770-1/2 (LKFS gated), an international specification that defines levels of measurement based on loudness, rather than peaks. 

Looking under the covers of BS 1770, we find several factors designed to address the subtleties of loudness in different types of programming and at different frequencies. For one, the ITU determined that higher frequencies are perceived as louder or more irritating than normal frequencies (from 100 to 1 kHz); therefore, in BS 1770, frequencies above 1 kHz are assigned a shelf amplification of up to 4dB. Since the reverse is true for lower frequencies (meaning that an increase in power at frequencies below 80 kHz actually attenuates), the assigned shelf amplification is up to 3dB. The sum total of these two effects is called K-weighting, which creates a curve used to weight frequencies according to consumers’ loudness perception. Channel weighting is another factor that normalizes the differences in mono, stereo, left/right, and rear audio channels. 

Not to be overlooked is gating, as specified in BS 1770-2, which takes into account silences and extremely quiet periods within a particular content segment. With gating, an average loudness value is derived for a complete program that does not take into account any values under 10 dB, and the gating value is applied to the K-weighting and channel weighting to ensure that the loudness is measured only when there is measurable sound. 
European loudness recommendations and legislation

With its Loudness Recommendation PLOUD R128, published in August 2010, the European Broadcast Union (EBU) has created a framework for broadcasters to measure and normalize audio using loudness meters and monitors instead of, or in addition to, peak meters. PLOUD R128 uses BSU 1770 for the base measurement with the loudness unit (LU) defined as a relative value of 1dB. For a given audio track, PLOUD R128 takes into account the gated K-weighting and channel weighting to offer up a single loudness value: the Loudness Unit Full Scale (LUFS), essentially a dB measurement. The magic number for the PLOUD R128 recommendation is -23 LUFS measured at a relative gate of -10 LU. This value is the designated target for normalizing program loudness with an allowance of +/- 1 LU (the extra LU recognizes that live programming needs a bit more tolerance for loudness than file-based, pre-recorded assets). 

Regulatory bodies throughout Europe are in various stages of enacting loudness legislation based on the PLOUD R128 recommendations. In Italy, for instance, AGCOM regulates loudness based on the customer experience post-set-top-box, after all audio processing has taken place. The CSA in France has tiered enforcement guidelines with maximum measurements and tolerances specified for both short-form and long-form content. In the U.K.,  the BCAP initiative is focusing on the variation in audio loudness between commercials and the preceding program. 

Options for loudness monitoring and logging
Against this regulatory backdrop, broadcasters and video service providers are scrambling to identify and install effective loudness measurement and monitoring tools. The most comprehensive solution is one that can continuously log and monitor loudness based on EBU guidelines, assist in troubleshooting and mitigating complaints, and provide a clear affidavit of compliance for regulators – helping broadcasters not only to avoid fees and penalties but also to deliver the highest quality of experience to their viewers. 
Until recently, the market has been severely lacking in practical solutions that can capture and store an array of individual loudness measurements, tied frame-accurately to video. For example, no straightforward solution has been available for a broadcaster that needs to store numerous measurements over time, such as an array of real-time loudness values for 14 channels, each with five audio tracks. This is changing as digital video logging solutions already in place for other compliance and quality assurance purposes begin to offer features for loudness measurement. Whether the content in question aired yesterday, two days ago, or a month ago, a logging system equipped with robust loudness measurement, logging and reporting capabilities offers immediate assurance of compliance without the need to re-run and sample broadcasts for loudness levels. One such system is the Volicon Observer, engineered to record aired A/V content 24 hours a day with plenty of capacity to measure loudness and store metadata as well.  

To play an effective role in loudness compliance, the monitoring system should be equipped to account for AC-3 dialnorm levels and should support global industry loudness specifications and regulations, including ITU BS.1770-1 and BS.1770-2, ATSC A/85 RP 2011, CALM Act, EBU R128 (Tech 3341/2), and ARIB TR-B32. The system should measure momentary (M), short-term(S), and integrated (I) content with adjustable short-form (<2 minutes) and long-form timeframes that make it easy to compare an ad’s loudness to surrounding channels. Another important requirement is the ability to provide daily as-run logs of all ads aired and key loudness data for those ads. In the event of a consumer complaint or EBU query, the broadcaster can quickly navigate through logged content to the suspect ad and export both audio and video, with the real-time loudness parameters burned into the video. No evidence is more convincing or unambiguous than this type of 
A/V affidavit. 

Some final advice
With a logging and monitoring system onboard that supports comprehensive loudness compliance, broadcasters can begin taking incremental steps to bring their operations up to speed. For Europe-based broadcasters, the first step is to normalize all content to -23 LUFS. This can be a tricky matter with network feeds that originate outside Europe and may be operating under different target levels; in this case, the monitoring system can help the operator monitor the feeds over long periods and issue corrective actions with examples of out-of-compliance content. For tape-based assets, it’s a matter of measuring loudness and compensating on the mixing; and for file-based assets, it’s fairly straightforward to measure and normalize the audio track to -23 LKFS. 

For live feeds, loudness monitoring and correction is handled at mixing; your goal should be to monitor loudness for large discrepancies since the regulatory bodies give more leeway for live content. Live loudness monitoring is not unlike the challenges sound engineers already face in making sure that audio feeds are coming in at the right levels. 
Finally, don’t make the mistake of trying to fix loudness levels on the fly (with the exception of mixing for live programming). The best approach is to monitor commercials as they air, and then pro-actively provide feedback to the operator so that corrective action can be taken before the discrepancies result in penalties – or, arguably worse, compromised quality of experience for viewers. Just think of the last time you were blasted off the couch by an overly-loud commercial. It’s a powerful incentive for change.

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