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2-42
INSTALLATION
Setting Preset Loudness Correctly in Dolby Digital Transmissions
• Adjusting MB Limiter Drive changes the Loudness Level meter's indication and
the amount of gain reduction in the loudness controller and peak limiter.
If you are processing for a Dolby Digital distribution channel and wish to customize
a factory preset, be aware of two major philosophies, one presented in ATSC Rec-
ommendation A/85 and the other in EBU Recommendation R 128.
ATSC A/85: If you wish to ensure that dialog levels are consistent from one program
segment to the next, use the 1101's CBS loudness meter as a reference for adjusting
a user preset's loudness. In this case, we prefer relying on the CBS Loudness Control-
ler to do final loudness control and turning the BS.1770 Safety Limiter off. Consis-
tent loudness of the "anchor element" (usually dialog) is the goal suggested in ATSC
Recommendation A/85, which is the basis for CALM Act compliance, and we prefer
this goal to strictly relying on the BS.1770-2 loudness meter.
EBU R 128: If you wish to ensure that integrated loudness as measured on a
BS.1770-2 meter is consistent from one piece of program material to the next, use
OPTIMOD-PC's BS.1770-2 loudness meter as a reference. In this case, you may wish to
active OPTIMOD-PC's BS.1770 Safety Limiter, which will constrain BS.1770-2 loudness
with a 10-second integration time from exceeding the setting of the BS.1770
control. However, note that R128 encourages mixing to achieve a wide
T
HRESHOLD
dynamic range, where some material may considerably exceed the target loudness
when measured on a "short-term" (three-second integration time; ungated)
BS.1770-2 meter. Moreover, R 128 requires online loudness control to be defeated if
upstream material is known to be pre-processed such that the integrated loudness
of each program segment (per BS.1770-2) is identical to the active dialnorm value
with a ±1 dB window. You can use OPTIMOD-PC's control API (see Section 6 of this
document) to switch the output source between either D
bypass gain) and P
ROCESSOR
controlled output). See step 6 starting on page 2-26 for a detailed discussion of set-
up.
See Using the ITU BS.1770 and CBS Loudness Meters to Measure Loudness Controller
Performance starting on page 3-73 for a comparison of the ATSC A/85 and EBU R
128 philosophies of loudness control.
The CBS and BS.1770-2 loudness meters' calibrations track the 1101's active D
value, which is either the D
value is set to G
D
IALNORM
set if this value is not set to G
The loudness meters are only calibrated to D
in I/O M
> C
S
OURCE
IXER
control becomes active. This control allows you to scale the loud-
M
S
ETER
ENSITIVITY
ness meter's sensitivity so that it indicates on-scale and is mainly useful to allow you
to compare the loudness of the 1101's "radio-style" presets and to assess the effect
of customizing those presets.
M
W
L
IXER
ITH
IMITER
R
IALNORM
EFERENCE
) or the D
LOBAL
IALNORM
.
LOBAL
is not set O
ONFIGURATION
ORBAN MODEL 1101
M
IRECT
IXER
(which provides the loudness-
(which applies to any preset whose
value in the active processing pre-
if the Dialnorm R
IALNORM
. If it is set O
, the L
FF
FF
(which sets the
IALNORM
EFERENCE
OUDNESS
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