Dolby Laboratories DP570 - Manual (Page 99)

A Guide to Dolby Metadata Dialogue Level
Dolby ® DP570 Multichannel Audio Tool User’s Manual 87
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 with DVDs.
The Scale
The scale used in the Dialogue Level setting ranges in 1 dB steps from –1 to –31 dB.
Contrary to what you might assume at first, a setting of –31 represents no level shift in the
consumer’s decoder, and –1 represents the maximum level shift. Here’s why:
Dolby Digital consumer decoders normalize the average output level—that is, the output
level averaged over time using the equivalent loudness method, Leq(A)—
to –31 dBFS (31 dB below 0 dB full‐scale digital output) by applying a shift in level based
on the Dialogue Level parameter setting.
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 requires 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.
A Simple Rule:
31 + (Dialogue Level value) = Shift applied
Example:
31 + (–21) = 10 dB
Setting the Dialogue Level parameter is an essential service to the listener. For your
listeners, setting this level properly means:
• The volume level is consistent with other programs.
• The DRC profiles you make available to them work as you intend.
Once dialogue level is set, you can set up DRC profiles to further benefit the consumer.
Note: Programs without dialogue, such as an all‐music program, still require a careful
setting of the Dialogue Level parameter. When setting the parameter for such
content, it is useful 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.
Note: The –31 dBFS Leq(A) should not be confused with the station reference level (often
–18 or –20 dBFS). It is common to have different Leq(A) values for program
material that has the same reference level. An average loudness level of –31 dBFS
Leq(A) is quite compatible with facilities running at a variety of reference levels.