DTV Audio Group Addresses Loudness Management

Mel Lambert, of content creators, reports from the NAB Show.

“Ensuring consistent loudness is a no-brainer,” stated Bob Dixon, director of sound design with NBC Olympics, at yesterday’s DTV Audio Group meeting in Las Vegas. “Drive as normal; just check the speedometer,” he advised, referring specifically to level-measurement techniques outlined in the ATSC A/85 recommended practice. “The target is an average of -24 LKFS [to ITU-R BS.1770 standards] with a true-peak metering reference of -2 dB FS.”

The DTVAG’s latest meeting, held the second day of the NAB Convention at the Alexis Park Hotel, addressed the pressing need for real-world loudness management following recent passage of the CALM Act. Moderated by DTVAG Executive Director Roger Charlesworth, the event was produced by Sports Video Group and sponsored by Blue Sky, Dale Pro Audio, Dolby, Linear Acoustics, Stagetec, and Wohler.

“The FCC has mandated the use of the ATSC A/85,” emphasized Advanced Television Systems Committee President Mark Richer, who described the group’s soon-to-be-released Annex J, “which contains the core requirements for establishing and maintaining consistent audio loudness.”

Tomlinson Holman, of the University of Southern California, suggested, “Mix with your ears and ensure that the anchor element [normally, dialog] matches the transmitted dialnorm metadata value.”

During a series of lively discussions about practical techniques for 5.1-channel audio production, several participants offered that standardized labeling of the 16 audio channels within an HD-SDI signal would dramatically streamline ingest and signal distribution. Kevin Cleary, a senior technical audio producer with ESPN, described a format that carries a pair of DTS-encoded music mixes, a discrete 5.1-channel mix plus other elements, back to the network’s production center in Bristol, CT. Tom Sahara, VP of operations and technology for Turner Sports, observed that the EBU R123 standard offers a number of usable labeling schemes, stating that “we need the ability to exchange material using standard guidelines.”

Recalling the speed of turnaround needed in edit bays during the latest Summer and Winter Games, David Mazza, VP of engineering for NBC Olympics unit, said that the network “generated LCR mixes with the center reserved solely for dialog, upmixed left and right channels to 5.1 surround, and then reinserted the center dialog. The results were more realistic than if we had just upmixed an L/R balance.”

Fred Aldous, a senior mixer with Fox Sports, revealed that the sports network plans to originate 5.1-channel mixes on-site, rather than upmixing.

Summarizing the need for sports and entertainment networks to commit to 5.1-channel production, Turner Sports’ Sahara emphasized that such strategic decisions can only be top-down. “There must be someone in a senior decision-making position that supports surround production,” he stated. “Without that commitment, it is difficult to build a consensus through the various departments from creative to finance. After all, it is a business decision.”