Meeting Topic: TV Audio Loudness Control
Moderator Name: John Combs
Speaker Name: Richard Cabot, Ed Simeon and Lon Neumann
Meeting Location: Sherman Oaks, CA
On Tuesday, February 26, the Los Angeles Section hosted a series of presentations and a roundtable discussion on Digital Television Loudness and the CALM Act. We were all treated to a fast-paced introduction to the CALM Act, as well as standards used, available metering products and solutions for ensuring compliance, and surround sound downmix issues as they relate to Digital Television Loudness.
The presentations started with Lon Neumann of Neumann Technologies, who covered the motivation behind and intent of the CALM Act, which was enacted in response to complaints from consumers about loud television commercials. He also set the stage for discussion of the tools and technologies required for broadcasters to stay in compliance.
Lon introduced us to some of the standards used to determine compliance, and discussed the paths to compliance, such as: Deemed compliance, which is accomplished with real-time processing, and Safe Harbor, which is done with certification of sources upstream. He also discussed enforcement. Surprisingly, the FCC relies almost entirely on a pattern of com- plaints from consumers for enforcement. A "pattern of complaints" from consumers will then trigger closer monitoring, and non-compliance can ultimately result in fines up to US$10k per day.
Lon then provided an overview of the Advanced Television Systems Committee/ ATSC's recently released Recommended Pr actice A/85: Techniques for Estab- lishing and Maintaining Audio Loudness for Digital Television, which includes recommendations for Monitoring, Measurement, Metadata, and Dynamic Range Control. He also enlightened us with the importance of proper room geometry for loudspeakers in the surround-sound listening environment for a person doing actual loudness listening, either for compliance spot- checking, or during production. Apparently there is a common tendency for left-, center- and right-channel speakers to be placed in a common plane, when they should actually be equidistant from the listener, i.e. placed in an arc. The proper placement geometry for speakers in a surround monitoring system which will yield accurate perception for loudness monitoring is covered in the ITU-R BS.775 standard.
Ed Simeone, CEO of Dedicated Marketing, presented an overview of the co mmercial products and solutions available for accomplishing compliance with the CALM Act. Mr. Simeone started us off with some of the history of level measurement, including the earliest attempts at metering in the 1920s, the Bell Labs VU standard for 600 ohms, the Peak Program Meter in Europe in the late 1930s, and the classic Mike Dorrough Model 40-A Loudness Moni-tor in 1980.
Research by organizations including McGill University led to the development of standards such as ITU-R BS.1770.1, which more accurately models the perceived loudness levels of multiple trained engineers listening to more than 10,000 sound clips. The BS.1770.1 measurement utilizes a k-weighted filter bank and mean-square power averaging to yield a Loudness K-weighted Full Scale (LKFS) number which closely represents perceived loudness. K-weighting consists of a high-pass filter to exclude big, "bassy" effects and a shelving filter for the head-related transfer function. The ITU-R BS.1770.1 (and .2, .3) Loudness Standards are now applied in the implementation of numerous available commercial products for metering and controlling loudness in real-time.
Metering products: There are hardware metering products from DK Audio, TC Electronic, Tektronix, WMF Harris, Day Sequerra, Linear Acoustic, and Qualis. There are also software-only, VST plug-in products available from Dolby, TC Electronic, Orban (which is free), Waves, Izotope, and Steinberg and others.
Processing products: There are also real-time processing products from Day Sequerra, Jünger, Linear Acoustic, Orban, TC Electronic and others.
Dr. Richard Cabot, of Qualis Audio, concluded the presentations with more discussion of the ITU-R BS.1770 Loudness Standard, Dolby's patented Dialog Loudness measurement, and Dialog Intelligence implementation issues. He also gave an in-depth discussion of surround-sound downmix issues related to Loudness. Here's one example: Most consumers listen in stereo, which can accidentally be (or gamed to be) nearly 4 dB louder than the Dialnorm would indicate. If you mix Left Front to -3 dB, Center Front to 0 dB, and Right Front to -3 dB, the resulting down mix (given default encoder settings) will be +3.72 dB hotter when all of the channels are correlated.
The meeting was concluded with a panel discussion, with questions fielded from the audience. Topics explored included: Use of Dynamic Range Control, the importance of correct Dialnorm values in content, use of Dolby's Dialog Intelligence, and how to file an FCC complaint.
Overall, the meeting provided us with concise and fast-paced introductions to the multitude of technology and legal aspects of Loudness management in modern Digital Television. The Los Angeles Section wishes to thank Lon Neumann, Ed Simeone and Dr. Richard Cabot for taking the time to share their expertise and broad knowledge with us on this timely subject.