Dolby Laboratories DP564 - Manual (Page 76)

DP564 Multichannel Audio Decoder Appendix A: Metadata
A-6
The most important point to remember is that in setting the dialogue level parameter,
you are providing your listener with an essential service. 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.
A.3 Dynamic Range Control
Different home listening environments present a wide range of requirements
regarding dynamic range. Rather than simply compressing the audio program to work
well in the poorest listening environments, Dolby Digital encoders calculate and send
Dynamic Range Control (DRC) metadata with the signal. This metadata can 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 DRC metadata
associated with the decoder’s selected operating mode.
The Dolby Digital stream carries metadata for the two possible operating modes of
the decoder. The operating modes are known as Line Mode and RF Mode due to the
type of output they are typically associated with. Line Mode is typically used on
decoders with six- or two-channel line-level outputs and RF Mode is used on
decoders that have an RF-remodulated output. Full-featured decoders allow the
consumer to select whether to use DRC and if so, which operating mode to use. The
consumer sees options such as Off, Light Compression, and Heavy Compression
instead of None, Line Mode, and RF Mode. Advanced decoders may also allow
custom scaling of the DRC metadata.
All that needs to be done during encoding is selection of the dynamic range control
profiles for Line Mode and RF Mode. The profiles are described in the following
sections.