Loudness Requirements Open The Door To New Creative Potential
11-16-2013 12:00 PM
Loudness requirements opening the door to new creative potential may seem like a very strong claim to make but recently Jon Schorah, creative director at Nugen Audio wrote a piece which I feel helps to explain how the loudness requirements and liberate us from the loudness wars where we have to crush the life out of our audio to make it sound louder than anything else. Jon writes…
By now, most of us are well aware of the need to measure and manage programme loudness in broadcast operations. With loudness standards and regulations now being introduced and enforced in many different countries, coupled with a real threat of fines for loudness infractions, the responsibility for compliance is increasingly falling on audio post-production engineers.
The good news: after working with loudness for even just a short time, many post-production engineers are finding new creative potential that simply wasn’t there with peak-level normalisation. Far from adding another complicating factor to the mixing process, loudness requirements actually allow the engineer more freedom to be creative, and they also reward expertise.
New tools for creative engagement
Simply compressing a mix to achieve a consistently loud level under loudness normalisation will probably just result in the audio being turned down. Therefore, the best way to achieve a mix that stands out in the crowd is to engage creatively with the content and make the most of the available dynamics. For engineers involved in short-form production, the increased headroom that results from pairing loudness normalisation with the use of true-peak maximum levels offers real rewards in the form of increased dynamic range and contrast that can be used creatively.
New loudness recommendations call for new tools - and fortunately for post-production engineers, companies are developing products specifically for them. Intuitive audio-editing tools such as real-time metering, offline correction, and loudness-compliant limiting allow post-production editors to put their creative expertise to work while staying compliant.
Loudness metering and true-peak limiters
The key to delivering high-quality, loudness-compliant audio is clear, intuitive loudness metering. Because the new loudness measurements are designed to correspond to the human ear, a good engineer can almost create a mix without a meter. It’s possible for skilled engineers in a calibrated room simply to glance at the meter occasionally during the creative process in order to maintain their bearings or to check something in particular. But in the end, even the experts need to confirm that they’ve met target values. Likewise, anyone looking to push creative boundaries would need to check to make sure they’re still in compliance. With a visual meter, editors can keep an eye on the meter and loudness profile while relying on their trained ears to make most of the decisions.
Going many steps beyond sample peak limiters, true-peak limiters are designed to handle the intersample true-peak requirement of the new standards. It’s tempting to use an existing sample peak limiter with a setting that yields results that are ‘safe enough’ to be compliant with the true-peak measure of the loudness standards. However, this is a risky approach because a sample peak limiter is not capable of providing an accurate true peak reading. The measurements are different, and what might seem like safe settings on a sample peak limiter would not guarantee compliance.
Efficient offline correction and batch processing
Once a mix is more or less loudness-compliant, editors can use offline tools to fine-tune the mix and complete the normalisation process. These time-saving tools can be plugged into the editing environment to bring a mix into line quickly, correcting any true-peak overshoots along the way.
Another time-saver is batch analysis, offering busy post-production operations a way to automate part of their loudness processing. Acting as a rapid fail-safe system and internal QA, a batch processor can automatically assess files for compliance and correct or reject them as appropriate.
Once broadcast compliance criteria are met, loudness measurement tools can provide a number of additional capabilities for enhancing audio in post-production. One such area is dialog clarity. Even today, mixes are occasionally broadcast with the background music too loud, resulting in indistinct dialog and viewer complaints. Engineers can guard against these mistakes by using a meter to preserve loudness separation for dialog above other mix components.
To help maintain consistency from section to section, engineers can measure the loudness of background music beds and FX spots. In sessions that require significant complex editing, loudness normalisation is a far more useful control than 0dBfs for quickly matching dialog levels.
For audio libraries, engineers can apply loudness normalisation to ensure that audio is always internally consistent and available at an expected level. It’s also useful to consider the LRA (Loudness Range) parameter when creating a mix for a specific target device.
Luckily for audio producers and post-production engineers, the various international loudness recommendations are all based upon the same ITU standard and there is general agreement within the industry about how to approach loudness control. However, some issues still need resolving - most notably the difference between a 5.1 mix and its corresponding downmix. While it’s common for the downmix to differ slightly in loudness from the 5.1 mix, the difference can be in either direction, so a simple offset is not a viable solution. Similar situations arise with dual-language, multi-mono stereo, where a consumer’s television can produce an unexpected 3 dB loudness jump depending upon the configuration. Relying on the metadata would be one solution, but that only works if the metadata is accurate and the appropriate device is capable of reading and responding properly.
Thanks to loudness normalisation, we’ve seen fewer complaints from consumers. Now it’s time to build on this solid foundation and start refining loudness control solutions. The ultimate goal is to make loudness a primary consideration during production. With the improvements in tools, engineers can use loudness parameters and transferable, objective measures to check whether or not audio is compliant - and also target-appropriate. And with the same tools, they can take things a step further to produce better-sounding, more creative mixes.
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