Turn down the volume
Jan 1, 2010 12:00 PM, By Dennis Ciapura
Uncle Sam plans to control digital TV audio.
The amended bill, which would be effective a year after passage, gives operators that can demonstrate hardship a one-year waiver with a possible one-year renewal, and this is a big loophole that many operators will jump through. This in turn will likely create an awkward mix of conforming and nonconforming outlets for some time, which may lead consumers to conclude that nothing much has changed, resulting in a continued flow of complaints to the FCC for years.
Understanding the technology
The least controllable element in the commercial loudness control challenge is consumer equipment in the field, and there can be some unexpected interactions with broadcast 5.1. For example, some commercials are not produced with 5.1 audio, but are transmitted as digital 5.1 with stereo audio “enhancement.” The receiver decoder senses the 5.1 digital input and applies whatever sonic processing the user has selected for normal 5.1 audio. This often results in phase-shifted mono or stereo audio that has an echo, which makes it louder than the surrounding program audio, even if the level is the same. In a mix with other commercials that have been properly encoded, this also creates a spot-to-spot differential.
And there are other anomalies. While most produced long-form programming these days comes with excellent 5.1 audio, local- and even some network-generated programs may lack true 5.1 capability. A convenient solution is to feed the available stereo audio to the left and right 5.1 channels. The problem with this is that home video/audio systems typically include a crossover to the subwoofer channel at 100Hz-200Hz. With no subwoofer input, the viewers get thin-sounding audio with the low end band limited by the crossover frequency. The subwoofer is essentially out of the picture — until a nice punchy compressed commercial comes along! In this age of sophisticated home video/audio, program producers and broadcasters must understand the technology that consumers are using.
Conclusion
The key to the successful implementation of the Recommended Practice, and heading off further government intervention, is in universal adoption. While the major networks and most major market affiliates can be expected to conform, the cable and satellite systems may lag. Local spot inserts in cable systems are a particularly weak point. These are usually local direct retail spots sold by local salespeople who are desperate to get their client's spots noticed. Hopefully, advertisers and their agencies at all levels will come to realize that the ATSC Recommended Practice is a far better solution than the viewer's mute button.
Dennis Ciapura is president of Performance Broadcasting, a broadcast management consulting company.
How to make your loudness comply
With or without additional government regulations, ATSC standards published back in the mid-1990s and adopted as the law by the FCC mandate that loudness be correct. If you didn't know that, you are not alone. There is no practical guidance as to how to make this happen. However, a new ATSC recommended practice attempts to distill a lot of information into one reference.
ATSC A/85 “Techniques for establishing and maintaining audio loudness for DTV” lays out a comprehensive plan for managing loudness from production to transmission. Essentially, it boils down to measuring content using an ITU-R BS.1770-compliant loudness meter to ensure that all audio either matches a loudness reference (-24 LKFS +/-2 ) or that the audio and corresponding metadata match. In either case, content that does not match can be rejected or adjusted, or metadata can be reauthored.
Guidance on both permanent and reversible dynamic range control is presented to help broadcasters understand the choices, and practical advice is given for setting monitor levels properly in production and post production so that an appropriate dynamic range will result during mixing and not be relegated to arbitrary adjustment later. A useful quick start guide is included to point readers directly to areas of interest.
What does a broadcaster need from the station side? At a minimum, you need a copy of A/85 and at least one real-time ITU-R BS.1770-compliant loudness meter to act as the station's DTV audio “mod monitor.” It may be wise to invest in more than one to allow monitoring of incoming content and to keep live productions in check. There's no need for mixers to worry; loudness meters work alongside the existing devices they are comfortable with.
Since the overwhelming passage of A/85 in November, broadcasters now have a reference to point to in their own delivery specifications and can send a clear and united message to program and commercial providers that they require loudness consistency in order to preserve audio quality, maintain legal compliance and most importantly satisfy viewers.
ATSC A/85 can be downloaded online at www.atsc.org/standards/practices.php.
Tim Carroll is the president and founder of Linear Acoustic.
| Want to use this article? Click here for options! |  |
