Sports Broadcasters Get Clarity on Loudness
The long-awaited ATSC Recommended Practices (RP) from the subgroup on Loudness Issues (Techniques for Establishing and Maintaining Audio Loudness for Digital Television), released last November, is helping formalize the loudness environment in an increasingly 5.1 broadcast world.
However, says NBC Universal’s Jim Starzynski, who chaired the subgroup, while positive momentum is building for programmers, networks, stations, and multichannel video programming distributors (MVPD)s to get loudness right, there is also a disconnect between content recipients and content creators when it comes to delivery and receipt of program specifications.
“A content recipient like a network will create a comprehensive document on how to prepare audio and video for delivery, but it was revealed that no mechanism really exists that guarantees the supplier’s technical staff will receive the document,” he explains. “This is especially true of short-form commercial content. We learned that we need to work with our suppliers, whether sports remote productions or program post houses, to fix this and eliminate this disconnect.”
One subtle but important change as a result of the new standards is the recommendation of loudness of -24LKFS and dialnorm to match if content is delivered without encoded metadata. Consensus for use of -24LKFS when specific content metadata or a separate agreement is not present was achieved in S6-3, the group that authored A/85.
“Considering NBCU uses a fixed-metadata approach without specific, agile encoding for individual pieces of content, use of this ATSC recommendation makes perfect sense. In fact, we understand that each major network and PBS are either already there or headed in the same direction,” Starzynski says.” This is a huge accomplishment and welcomed byproduct of the very successful ATSC committee process that developed the RP.”
5.1 and Loudness
While loudness issues have been around since the dawn of broadcast television, surround — and its ubiquity in sports telecasts — can complicate the equation, causing “level creep.”
“Improper management of the surrounds will negatively impact loudness,” Starzynski says. “The surrounds are as much a contributor to the essential BS-1770 measurement to achieve specified LKFS loudness as the center channel. Poorly mixed and monitored surround channels have a way of dominating an otherwise good mix and drowning out the announcers.”
Bruce Goldfeder, director of engineering at CBS Sports, says it can also be just the opposite. Referring to a recent football game in Florida, he recalls, “We were having a hard time with the RF parabolas picking up wideband noise. If it had been mixed in with the announcers, we would never have known where it came from. But having the effects in discrete channels is a plus. It helps you isolate and manage noise, and that affects loudness, too.”
He says he decided against implementing loudness metering last year after determining that his mixers were remarkably consistent regarding the anchor parameter, the announcer’s level. Instead, he discovered that the variations in loudness were mainly in the effects audio.
Goldfeder monitors the first 10-15 minutes of a game, offers the mixer guidance on the relative levels of announcer and effects, and then lets go. “After realizing that [the announce levels of] all of our mixers were within one or two dB of each other on their own,” he says, “we didn’t want to implement any strict regulation that could tie their hands.”
Starzynski adds that NBCU instructs its mixers and suppliers to monitor the downmix frequently. “The stereo downmix of the 5.1 is the first place our audience will notice a problem with overly loud rear channels.”
Ultimately, the new Recommended Practices have both focused the loudness issue and unified response to it. The bottom line, says Starzynski: “If loudness in LKFS units equals dialnorm value and this is applied by all programmers across the dial, all the problems go away. The ATSC RP eliminates all ambiguity about how to do loudness for DTV.”