Dolby Laboratories Multichannel Audio Tool DP570 - Manual (Page 103)

Dynamic Range Control
Dolby ® DP570 Multichannel Audio Tool User’s Manual 87
Dolby Digital consumer decoders normalize the average output level—that is, the output
level averaged over time—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 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.
D.3 Dynamic Range Control
Different home listening environments present a wide range of requirements for dynamic
range. Rather than simply compressing the audio program at the transmission source to
work well in the poorest listening environments, Dolby Digital encoders calculate and send
DRC metadata with the signal. This metadata can then be applied to the signal by the
decoder to reduce the signal’s dynamic range.
Through the proper setting of DRC profiles during the mastering process, the content
producer can provide the best possible presentation of program content in virtually any
listening environment, regardless of the quality of the equipment, number of channels, or
ambient noise level in the consumer’s home.
Many Dolby Digital decoders offer the consumer the option of defeating the Dynamic
Range Control metadata, but some do not. Decoders with six discrete channel outputs (full
5.1‐channel capability) typically offer this option. Decoders with stereo, mono, or
RF‐remodulated outputs, such as those found on DVD players and set‐top boxes, often do
not. In these cases, the decoder automatically applies the most appropriate DRC metadata
for the decoder’s operating mode.
Note: The –31 dBFS should not be confused with the station reference level (often –18 or
–20 dBFS). It is common to have different values for program material that has the
same reference level. An average loudness level of –31 dBFS is quite compatible
with facilities running at a variety of reference levels.