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Adapting dynamics for various playout scenarios

Adapting dynamics for various playout scenarios
Jon Schorah


01 January 2016: By Jon Schorah

Nugen's Jon Schorah explains how the rise of mobile streaming and portable devices has led to new loudness complications.

Nugen Audio founder and creative director Jon Schorah explains how the rise of mobile streaming and portable devices has led to new loudness complications and suggests how they can be overcome.

It’s been quite a while since loudness standards were first introduced (with Europe adopting EBU R128 in 2010 and the US gaining the CALM Act in 2011) and, for many of us, producing audio to these specifications has become a familiar daily routine. As a result, consumer complaints due to programme loudness jumps are down, and the consistency of listening levels from channel to channel is greatly improved.

Although loudness regulation was originally designed to apply only to television programming, the wide-ranging benefits of loudness normalisation for increasing customer satisfaction have led to its consideration and application in other aspects of consumer audio. A major driver is the revolution in mobile streaming and the vast increase in the use of portable devices, even within the home, which have brought about dramatic changes in audio consumption over the past five years. Therefore, a regulation that was originally designed for the relatively controlled environment of home television has begun to be tested and stretched when applied to the multitude of additional offerings for which audio quality is also an important factor.

Mobile consumption in particular presents a new set of complications. The mobile listening environment is often a noisy place, since cars, public transport, open spaces and busy offices are filled with ambient sound. Low-level audio that might be perfectly acceptable in the home can be very difficult to hear clearly in more public environments.

In addition, audio is often delivered to the mobile listening device via a streamed data connection. When data bandwidth is in short supply and rigorous data compression techniques are employed, the streamed data can suffer from codec distortion.

Finally, the playback device itself often provides limited playback gain and headroom, resulting in poor control over output level and/or distortion at high levels of applied gain.

In combination, these issues can mean that the standard EBU -23 LUFS/ATSC -24 LKFS, -1dBTP and widely dynamic materials are unsuitable for many of today’s consumption patterns. As broadcasters look to repurpose broadcast material for such uses as internet streaming, radio and smartphones, a parallel set of target requirements is emerging.

Standards and recommendations are evolving to address these issues; for instance, the recently published AES TD1004.1.15-10 proposes a loudness window of -20 to -16 LKFS for streaming audio, and a similar consideration is underway in the EBU Ploud committee.

Streaming ahead

In practice, many well-known streaming services are now applying loudness normalisation ahead of formal recommendation simply because of its benefits to their consumers. Perhaps the most well-known and publicised example is the adoption of approximately -16 LKFS by Apple in iTunes Radio.

These loudness levels, several dBs above the television targets, address the issues of noisy environments and problems with playback gain. However, repurposing existing work using traditional audio compressors can lead to a significant decrease in quality, such as loss of dialogue clarity – and preserving quality by employing level-riding by hand can be difficult and time consuming.

Ultimately, it may be possible to deliver broadcast television-standard audio to any device, with appropriate metadata allowing the device itself to make appropriate adjustments (including true-peak limiting) depending on the environmental conditions and device specification. But we’re not there yet.

At Nugen Audio, we specialise in producing practical solutions to challenging audio tasks. The consumer is demanding audio that is ‘fit for purpose’, be it high-quality 5.1 audio for the home cinema or consistent audio with distinct dialogue for consumption in a mobile environment. These diverse demands place increased pressure on budgets and busy production schedules, and they are driving a requirement for high-quality content repurposing.

In response, Nugen Audio has developed a new algorithm to address multiple delivery specifications and audio dynamics simultaneously, while also respecting the level of dialogue in the mix to avoid introducing the dialogue clarity issues commonly associated with similar solutions. Our DynApt (Dynamic Adaptation) algorithm, currently available as part of our off-line batch-processing tool or as an NLE plug-in, allows audio repurposing and complex loudness-compliant dynamic adaptation (including LRA targeting) within the NLE as part of the creative process. Running much faster than real time, this process delivers significant repurposing power into the hands of post-production professionals with minimal workflow disruption, while eliminating the need to remix the work several times for each target platform.

With these new tools and the use of flexible loudness metering, the task of producing multiple audio versions need not be a significant challenge. In fact, since many international broadcasters (both TV and radio) are already applying these new tools in their day-to-day programming, the chances are good that you have already heard the results!