DTV Audio Group Seminar Tackles Loudness Management
By Mel Lambert
Held at the Alexis Park Hotel and Casino, Las Vegas, on April 11th, the DTV Audio Group’s Loudness Management Seminar attracted a broad cross section of industry professionals who gathered to discuss the thorny question of controlling digital television loudness levels. The 100 plus attendees included engineering and operational staff from the major network and post-production facilities, in addition to content providers and hardware manufacturers. The event, coordinated by Sports Video Group, was made possible by sponsorship from Bexel, Calrec, Dale Pro Audio, Day Sequerra, DTS, Dolby Labs and Linear Acoustic.
The event’s theme was in keeping with DTV Audio Group’s stated mission of helping broadcasters meet the potential of digital television audio through education and communication initiatives, and underscored the importance of the group’s emphasis on operationalizing technical standards and procedures in real-world production environments.
Focus of the afternoon seminar was an overview of the Advanced Television System’s Committee’s (ATSC) recently released Recommended Practice A/85: Techniques for Establishing and Maintaining Audio Loudness for Digital Television; presenters and panelists included a number of audio experts that have been working for the past two years to develop the recommendations, in addition to representatives from the community of professionals that are currently implementing its contents. The 66-page A/85 document provides a thorough overview of loudness management and defines a number of best practices for a range of broadcast and post-production applications.
“Controlling the audio loudness of digital television continues to pose challenges for networks, local TV stations, cable/satellite operators and other multi-viewer program distributors,” Roger Charlesworth, president of Charlesworth Media, and Executive Director of the DTV Audio Group, offered during his opening presentation. “Ineffective DTV loudness management has lead to widespread viewer complaints, and the threat of legislative and regulatory action.” The Commercial Advertisement Loudness Mitigation Act (CALM) recently passed through the House and is currently with the Senate Commerce Committee; RP A/85 is critical to addressing the act’s concerns, Charlesworth considered.
“Improvements in audio capability of the ATSC AC-3 multichannel audio system pose several equal-loudness challenges,” continued Tomlinson Holman, Professor of Film Sound, University of Southern California, during his presentation From Analog to Digital; Background on DTV Loudness and Impact on Government and Industry. Holman contrasted the severely limited dynamic range of the incumbent NTSC system with the significantly more powerful DTV audio standard, and outlined the use of K-weighting meters with LKFS scales to the ITU-R BS.1770 standard to ensure loudness consistency with uniform average perceived loudness of dialog levels; this enables Dialnorm metadata that forms part of the AC-3 bit stream to indicate the average dialog loudness within a coding system’s dynamic range.
During his presentation, Working it Out Together; Summary of the S6-3 Subcommittee Process, Pat Waddell, Manager, Standards and Regulatory, Harmonic Inc, and Chairman ATSC TSG/S6, outlined the progress towards formulation of the ATSC A/85 Recommended Practice, including the work of two ad-hoc groups that addressed the key issues of program loudness and AV synchronization. Waddell stressed the due-process nature of the document, which ensured its wide industry consensus agreement.
A panel discussion entitled Where is it Going Wrong? Identifying Real-World Loudness Challenges, moderated by Charlesworth, reviewed the importance of loudness-management practices and potential causes for error. Panelists comprised Matt Braatz, SVP, Broadcast Operations, NBC Universal; David Converse, VP Operations, Director of Engineering for ABC Owned Stations; Craig Cuttner, SVP, Advanced Technology, Home Box Office; Jim DiMattia, Verizon Communications; Doc Goldstein, VP Sound Engineering, NBC Universal; and Burke Moody, Executive Director, Association of Independent Creative Editors. “We need agreement across all networks and TV channels,” Moody emphasized. “Then we can get conformity loudness levels from all advertisers!” “Producers want shows that compete with commercials,” Goldstein considered. “Standards are very important, since they allow the show’s producers to get what they want, and also ensure that the loudness levels fit within our own specifications.”
Chaired by Jim Starzynski, Principal Engineer, NBC Universal, Understanding and Implementing ATSC A/85 provided a lively discussion during which Steve Lyman, Senior Staff Engineer, Technology Strategy at Dolby Labs, focused on Measurement Techniques, while Holman provided an overview of Monitoring Processes, and Tim Carroll, President of Linear Acoustic, Inc., reviewed ATSC Metadata Requirements. Sean Richardson, Senior Manager Post Production/Principal Audio Engineer, Starz Entertainment, reviewed Loudness Recommendations for Program Exchange, while Starzynski considered the problematic issue of Program to Interstitial Loudness.
Richard Friedel, Executive Vice President, Fox Networks, Operations and Engineering, provided a summary of A/85’s Quick Reference Guides, followed by Ken Hunold, Broadcast Applications Engineer with Dolby Laboratories, who reviewed AC-3 Reversible Dynamic Range Control and Carroll on Modern, Conventional Dynamic Range Control. Repeatedly the presenters returned to what Friedel characterized as the “Golden Rule” of RP A/85; “The emissive dialnorm value needs to match the measured average loudness of the program. Loudness management is that simple”
The final panel discussion, Putting it into Practice; Implementing Practical Solutions Based on ATSC A/85, moderated by Charlesworth, considered real-world operational and engineering solutions that take advantage of A/85 recommendations to ensure loudness quality and consistency. Panelists included Richard Buchanan, VP of Content Operations & Engineering, Comcast Media Center; Ivan Larsen, Director of I.T. Operations, Time Warner Cable Media Sales; Hank Frecon, Managing Director of RadiantGrid Technologies; Steven Silva, Director of Training and Procedures, Fox Networks, Engineering; Robin Thomas, Group Director, Engineering, ABC; and Starzynski from NBC Universal. “For three years we have been using a Dolby DP600 processor to measure and correct loudness levels on commercial insertions in a file-based workflow,” confirms Time Warner Cable’s Larsen. “We run thousands of spots a month, and as soon as the media walks in the door, we are time bound; we might have a three-hour play-out window. Efficiently automating loudness correction is critical to our operation.”
Tom Sahara, Senior Director Remote Operations and Information Technology, Turner Sports, and Chairman of DTV Audio Group, wrapped up the proceedings with a presentation entitled Getting It Out There; DTV Audio Group, Loudness Management On-Line Training Initiative, during which he described the elements of an on-line tutorial from the group that is designed to make it easier for production personnel to understand critical aspects of the A/85 Recommended Practice. “We have identified 16 points in the audio chain from the announcer to the consumer’s TV set at which audio might be manipulated. A small 0.5 dB variation at any of these steps can cause a major level change” for the listening audience. “Our on-line guide will be targeted at mixers and operators, to provide a simple-to-use reference to A/85.”
Photos from the DTV Audio Group Seminar: