As more and more facilities come online supporting audio metadata and its carriage to consumers, it is very important to note an often-overlooked problem. As metadata is not actually applied to the audio until after delivery to consumers, it is easy to misinterpret audio that looks or sounds incorrect. Until metadata is applied to it, no proper judgment can be made. This is an increasingly common mistake made by even the best engineers.
Improper monitoring of audio occurs more frequently today because of the quantity of audio programs that rely on metadata and a corresponding lack of gear that takes into account how metadata should be used. Dialog loudness, for example, controls a 30 dB attenuator that is applied post-decode at the consumer side. If the value is set to -21, then 10 dB of attenuation will be applied, and if the value is -31 then no attenuation will be applied, etc... However, this means there may be programs that differ substantially in level and will look wrong on meters and sound wrong on speakers--unless the accompanying metadata is also applied. If metadata is not applied, operators may believe there is a need to correct a program that looks too low on the meters. They may not realize that if they do adjust the levels, metadata may make the problem far worse.
There are other values that must also be applied for accurate monitoring, but dialnorm will cause the most confusion with operators. Make sure the gear you purchase has the ability to properly display audio with respect to its accompanying metadata. And remember this applies to all gear that handles audio in a modern DTV plant.
