Audio quality vs. loudness compliance

So, here we are, just on the other side of the start of enforcement of FCC rules concerning the loudness of commercials in digital television. Today, loudness issues are much better understood, and significant progress has been made with solving disparities. Things are noticeably better than before, except for one thing: Audio quality largely pays the price for compliance.

Compliance is understood to mean a lack of regular complaints to the FCC by viewers. One technique is Automatic Gain Control (AGC), which raises or lowers gain on a sample-over-sample basis. This keeps audio loudness centered on a given static target. It is a relatively easy answer for compliance and is fully supported by both A/85 and the FCC Report and Order. However, AGC achieves its goal by more or less treating every shift similarly, correcting the bad — and the good. Everything gets a little something, whether it needs it or not. Sounds like a recipe for mediocrity.

Although there are sophisticated (and some unsophisticated) ways to accomplish AGC, no machine — regardless of manufacturer, topology or promise of magic outcome — can in real time know the difference between a good, intentional loudness shift and a bad, annoying loudness shift. Certainly, human-generated commands or automation can be used to change or bypass processing for content that is believed to be good, but thus far, this involves a great deal of effort and is uncommon.

Mix engineers have long resigned themselves to the fact that what was transmitted over analog television would be different from what they created. That was just the way it was. In today’s digital world, there is not any technical reason why before and after cannot match. In general, this successfully occurs when films mixed for the big screen are transferred to DVD. Helpfully, the same audio coding system, Dolby Digital, is used for digital television.

Beyond average loudness

Looking more broadly at the program stream, loudness problems have to be considered both an issue of matching the average loudness of commercials and programs and one of inner-program consistency, also known as artistic dynamic range. Matching average loudness of different pieces of content does not solve the problem of jarring transitions. These occur at program boundaries and can be the result of a mismatch of dynamic range and/or the short-term loudness at the junction between the end of one piece of content and the beginning of the next.

Think of a program whose average loudness measures at one level and a commercial that measures at another level. If their averages are matched by scaling to a target, on average they will sound equally loud. However, if a dramatic program is ending with a quiet death scene (as they often do) and is quiet compared to the average of the 60 seconds leading up to the commercial, guess what is about to happen? Yep, the commercial will seem too loud. Guess what else? Meters will be totally happy, because they are looking at long-term averages. Viewers will not be so happy.

This is subtly different from intentional dynamic range variation, such as a loud train crash or gunfight in an action adventure movie, as it is an unexpected variation caused by automating disparate elements together, and it just sounds wrong. In fact, the difference in loudness in this case may be much less than the gunfight, but it is perceived as much worse.

Permanent AGC techniques can probably keep the passive couch potato happy, but the programming will be irreparably changed, and the producers probably will not be thrilled with the results.

The best producers know they must make programs dynamic and engaging for those viewing with surround systems, without going too far and alienating the core audience listening in stereo (estimated to be in excess of 70 percent of viewers), and all while remembering that there might be a dynamic commercial randomly inserted.