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INTRODUCTION
ORBAN Model 6200
Availability of multiband compression is another argument for passing most program
material through a conventional compressor with loudness control even in DTV service.
Multiband compression smooths out not only loudness variations but also variations in
equalization, which can be particularly valuable with program material that has to air in
a timely manner, where there is no time budgeted for careful audio post-production. Ma-
terial that airs with full Dynamic Range Control implemented should be refined so that it
sounds polished and consistent without further processing. A considerable amount of
televised material does not meet this criterion.
Using the 6200 in the 5.1 Channel Plant
The following is one potential scenario for installing the 6200 in a 5.1 channel plant.
Obviously, other, more complicated switching arrangements could also be designed. The
only crucial requirements are keeping the time delay of all channels equal and compen-
sating for the delay of the 6200, which will ordinarily be padded to 1 frame in this appli-
cation.
In a full 5.1 channel plant, the channels ordinarily used to transmit 2-channel material
should be applied to the 6200's input and to one input of an AES/EBU switcher. A sec-
ond input of the AES/EBU switcher receives the 6200's output. The output of the
switcher drives the channel 1/2 input of the Dolby AC-3 encoder. The remaining 3.1
channels are applied directly to the AC-3 encoder.
The 6200 is configured for one-frame delay. The AC-3 encoder is configured with a pre-
set that (1) reduces its delay by one frame, (2) defeats the AC-3 encoder's internal DRC
compressor, and (3) puts the AC-3 encoder into two-channel mode. This preset is acti-
vated whenever the AES/EBU switcher chooses the output of the 6200 as the input
source for the AC3 encoder's channel 1 / 2 input. As discussed earlier, this configuration
is made active whenever the station is transmitting "garden variety" program material
and wants the advantages of automatic loudness control and multiband compression.
If the AES/EBU switcher has a delay, it will be necessary to put a matching delay in the
other 3.1 channels to ensure that phasing is maintained in 5.1 channel operation.
Bypassing the Loudness Controller
The Loudness Controller can reduce the impact of sound effects in dramatic program-
ming, so the broadcaster may wish to defeat it during such programming and turn it on
during breaks and commercials. To do this, temporarily edit your on-air preset to turn off
the loudness controller, and save this edited preset as a new user preset. To turn the
loudness controller off and on, recall the appropriate preset.
The 6200 in 2-Channel DTV Applications
Some DTV systems (such as DBS satellite) specify two-channel audio and do not pro-
vide for metadata. The general comments above regarding 6200 audio processing apply,
but the system can be much simpler because no bypassing of the 6200 is required. We
recommend padding the 6200's delay to one frame of the system in use (which can be
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