CALM Act, Suppliers Give Broadcasters the Tools To Manage Loudness
Last year was the first full year of implementation for the ATSC Recommended Practices (RP) from the subgroup on Loudness Issues (Techniques for Establishing and Maintaining Audio Loudness for Digital Television, or RP-A/85), a hefty document that sets guidelines and methods for addressing audio loudness across television programming.
RP-A/85 brought television broadcasters an agreed-upon scheme to measure, monitor, and manage audio loudness for both HD and SD content, as well as recommending production, distribution, and transmission practices to third-party audio-content developers for providing the highest-quality audio deliverables to DTV broadcasters. RP-A/85 further suggests methods to control program-to-interstitial loudness, describes modern dynamic-range control, and addresses metadata and its role in the process.
This year, recently passed legislation bolsters the standards. The Commercial Advertisement Loudness Mitigation (CALM) Act requires commercials to be at the same loudness levels as programs during which they play. CALM gives the FCC a mandate to regulate and enforce volume limits on commercials, ensuring that their maximum loudness does not exceed the average maximum loudness of the program they’re accompanying and requiring the use of the practices in A/85. Advertisers will have one year to implement technology to keep volume levels in check.
Linear Acoustic President Tim Carroll calls the standards and the legislation “a good start” but adds that the standards can’t solve the problems by themselves. “Everyone has to pay attention to it to make it work. Everyone has to use the meters and be honest about the results, and broadcasters have to make their standards available to the people who create the content.”
That last point underscores how the legislation affixes responsibility, putting the onus of compliance on the broadcaster rather than the advertiser or other content provider. “It’s not like we need more government in our lives, but at least the CALM Act gives broadcasters something to fall back on, to back them up in the event they’re not getting the cooperation they need,” Carroll says. “It finally has the force of law, and broadcasters can say [content] has to meet certain standards and that we have the right to reject it if it doesn’t.”
NBC Universal Principal Engineer Jim Starzynski, who chaired the ATSC Recommended Practices (RP) subgroup, says implementation has actually been good across the board, starting with his own network.
“At NBCU, we completed our A/85-compliant loudness-normalization initiative across the entire company at the end of October of 2010,” he says. “This includes the NBC TV network, all of our cable properties, each NBCU and Telemundo owned-and operated station. Now each commercial and every promo match programming at the ATSC-specified -24 LKFS. We’ve accomplished this by enforcing our delivery specification and by scaling and processing short-form content, if necessary.
“Elsewhere,” he continues, “we’ve seen a lot of positive momentum, and audio loudness is getting better in many markets across the country. Each network or supplier has their own method to fix loudness, and A/85 has become the benchmark paper to refer to when broadcasters, cable operators, and satellite services make their decisions.”
Surround for Sports Broadcasting
A/85 was designed with the increasingly common application of surround audio for sports broadcasting in mind. “A/85’s measurement techniques based upon the ITU-R BS.1770 international standard apply identically to both stereo and 5.1 soundtracks,” Starzynski says. “An engineer mixing or measuring content does not have to adjust the meter whatsoever to take readings for either. Just apply the audio and observe the data.”
Nonetheless, he notes that users have occasionally misinterpreted one aspect of the RP. “When A/85 recommended -24 LKFS as a loudness for content exchange when metadata is not supplied with the material, it’s crucial that users understand that the -24 LKFS value refers to the average of long-term loudness of the anchor element of the content, not the instantaneous loudness some have misunderstood it to be,” he explains. “Correctly using -24 long-term loudness, content suppliers are able to supply soundtracks with excellent dynamic range and segues that match interstitial content during their programming.”
Education is the key to this, Starzynski says. “We’re still helping the production community understand that the two-[track] mix the audience hears on their DTVs and from their set-tops is created ‘on the fly’ during the 5.1 broadcast in the consumer’s equipment. This is why it is essential that mix engineers listen to their content in both 5.1 and two-channel before they deliver it to the recipient. Even if a two-channel mix is supplied with the 5.1 mix on the tape or in the file, the two-mix will not be aired. A monitoring tool that simulates how a consumer device reacts to the audio and metadata, such as a Dolby DP 570, is required to do these simulations effectively.”
Meeting the Loudness Requirement
There are several ways to conform to the loudness requirement of matching dialnorm to content. The most direct method is to simply match all of the specifications listed in the content recipient’s document. However, scaling (measurement and loudness shifting by a server) of file-based content is an excellent non–quality-altering technique that a station or MVPD can apply, Starzynski points out.
A third approach, loudness-targeted processing, is a good choice if the first two practices are not possible. However, he adds, processing can alter the content, though slightly. If no specification is available, the ATSC recommends delivering long-term average loudness of the anchor element (dialog for long-form programs and overall loudness for short-form promos and commercials) at -24 LKFS.
“Audition your two-channel downmix with a metadata-based monitoring tool prior to delivery. Don’t exceed a true peak level of -2 [dB], and you’ll be delivering compliant soundtracks with excellent dynamic range that are very well suited for the DTV audience,” he says. “It’s that simple.”