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Linear Acoustic LA-5180 Metadata Frame Sync/Generator Operation Manual
7.3
The Three D's
The three most critical types of metadata parameters, Dialog Level, Dynamic Range Con-
trol, and Downmixing, are discussed in detail below. Channel Mode, which determines
how many audio channels will be Dolby Digital encoded, is equally important, with the re-
maining parameters falling in behind.
7.3.1
Dialogue Level
Dialogue level (also known as dialogue normalization or dialnorm) is perhaps the single
most important metadata parameter. The dialogue level setting represents the average
loudness of dialogue in a presentation.
When received at the consumer's decoder, this parameter setting determines the level shift
in the decoder that sets, or normalizes, the average audio output of the decoder to a preset
level. This aids in matching audio volume between program sources.
The proper setting of the dialogue level parameter enables the Dynamic Range Control
profiles chosen by the content producer to work as intended in less-than-optimal listening
environments, and is essential in any content production, whether it is for transmission in
a broadcast stream or for direct distribution to consumers, as in DVDs.
In broadcast transmission, standard setting of dialogue level ensures that the consumer can
switch channels or watch a television program without having to adjust the volume control
during commercial breaks. Using that standard for all content, whether conveyed by
broadcast television, DVD, or other media, enables the consumer to switch between
sources and programs while maintaining a comfortable listening level.
Note:Programs without dialogue, such as an all-music program, still require a careful set-
ting of the dialogue level parameter. When setting the parameter for such content, it is use-
ful to compare the program to the level of other programs. The goal is to allow the
consumer to switch to your program without having to adjust the volume control.
The Scale
The scale used in the dialogue level setting is from -1 to -31 dB in 1 dB steps. Contrary to
initial logic, a setting of -31 represents no level shift in the consumer's decoder, and -1 rep-
resents the maximum level shift. Here's why: consumer decoders standardize the average
loudness (averaged over time by the formula LeqA) to -31 dBFS (31 dB below 0 dB full-
scale digital output) by applying a shift in level based on the dialogue level parameter set-
ting. When a decoder receives an input signal with a dialogue level setting of -31, it applies
no level shift to the signal because this indicates to the decoder that the signal already
matches the target level and therefore requires no shift. In contrast, a louder program re-
quires a shift to match the -31 dB standard. When the dialogue level parameter setting is -
21, the decoder applies a 10 dB level shift to the signal. When the setting is -11, it applies
a 20 dB level shift, and so on.
38
Metadata
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