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Dolby® Encoding and Monitoring
Loudness Method
The Loudness Method control (7-5E) determines which processing algorithm is used to achieve an ATSC
A/85-compliant output.
Linear Acoustic APTO is the same algorithm used in the Linear Acoustic ARC television processor which
provides dynamic range processing and loudness leveling to transparently deliver audio that is both appropriately
dynamic (to maintain the creative intent of the program producers) and well-controlled (to ensure CALM-com-
pliance).
The Dolby Real Time Loudness Leveler, the same algorithm used in the Dolby AC-4 codec, normalizes the
incoming audio signal to achieve ATSC A/85 compliance.
Dialogue Normalization
The Dialogue Normalization control (7-5C) sets the dialnorm metadata value in the Dolby AC-3 or E-AC-3
bitstream, which is the same as the desired output loudness target level. For ATSC A/85, this is normally set to -24dB.
Advanced Dolby Digital Plus Encoder Menu
The advanced parameters menu contains controls that determine whether certain settings and metadata values
are set automatically or manually, and, if set manually, the values of individual settings.
Preferred Downmix Method
The Preferred Downmix Method control (7-6A) sets the downmixing metadata value for the downstream
decoder.
Not Indicated: No instructions to the downstream decoder are specified, allowing the decoder or the end
♦
user to choose the downmix type
Lt/Rt: The surround channels are added in-phase to the Left channel and out-of-phase to the Right channel,
♦
allowing a Dolby Surround Pro Logic decoder to reconstruct the Left, Center, Right, and Surround channels
Lo/Ro: The Center and surround channel content is redirected to the Left and Right channels for playback in
♦
a system with only two speakers
Line Mode
The Line Mode control (7-6B) sets the DRC (dynamic range control) profile for the line level output on home
decoders and set top boxes. It typically uses a profile that uses lighter compression and allows the viewer some
latitude in adjusting and scaling the amount of dynamic range as appropriate for their individual listening environ-
ment.
Chapter 7 | 40
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