Dolby Laboratories Multichannel Audio Tool DP570 - Manual (Page 106)

90 Dolby ® DP570 Multichannel Audio Tool User’s Manual
A Guide to Dolby Metadata
• Speech
Max Boost: 15 dB (below –50 dB)
Boost Range: –50 to –31 dB (5:1 ratio)
Null Band Width: 5 dB (–31 to –26 dB)
Early Cut Range: –26 to –16 dB (2:1 ratio)
Cut Range: –16 to +4 dB (20:1 ratio)
• None
No DRC profile selected. The dialogue level parameter is still applied.
These choices are available to the content producer for both Line mode and RF mode. The
content producer chooses which of these profiles to assign to each mode; when the
consumer or decoder selects a DRC mode, the profile chosen by the producer is applied.
In addition to the DRC profile, metadata can limit signal peaks to prevent clipping during
downmixing. This metadata, known as overload protection, is inserted by the encoder only
if necessary. For example, consider a 5.1‐channel program with signals at digital full‐scale
on all channels being played through a stereo, downmixed line‐level output. Without some
form of attenuation or limiting, the output signal would obviously clip. Correct setting of
the Dialogue Level and DRC profiles normally prevents clipping and unnecessary
application of automatic overload protection.
D.5 Downmixing
Downmixing is a function of Dolby Digital that allows a multichannel program to be
reproduced over fewer speaker channels than the number for which the program is
optimally intended. Simply put, downmixing allows consumers to enjoy a DVD or digital
television broadcast without requiring a full‐blown home theater setup.
As with stereo mixing where the mix is monitored in mono on occasion to maintain
compatibility, multichannel audio mixing requires the engineer to reference the mix to
fewer speaker channels to ensure compatibility in downmixing situations. In this way,
Dolby Digital, using the metadata parameters that control downmixing, is an “equal
opportunity technology,” in that every consumer who receives the Dolby Digital data
stream can enjoy the best audio reproduction possible, regardless of the playback system.
It is important to consider the output signals from each piece of equipment that can receive
a Dolby Digital program in the home.
Table D‐2 shows the output types from different
equipment.
Note: DRC profile settings are dependent on an accurate dialogue level setting. Improper
setting of the dialogue level parameter may result in excessive and audible
application of overload‐protection limiting.
Table D-2 Outputs from Different Equipment Types
Equipment
Output
Digital
5.1-Channel
Analog
2-Channel
Analog
RF
Remodulated
5.1‐channel amplifier
The standard home theater
A/V amp
Ч Ч
5.1‐channel decoder Ч Ч