2-Band Purist Processing; Input/Output Delay - Orban OPTIMOD 6300 Operating Manual

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OPERATION

2-band Purist Processing

Input/output Delay

ceeds 2 dB, and is indicated by the amber section of the L
meter in 6300 PC Remote. The gain reduction produced by the CBS Loud-
ness Controller may change slowly or quickly (depending on the nature
of the program material), appears in cyan, and rides on top of the
BS.1770 gain reduction. The peak reading of the meter thus shows the
total gain reduction that both controllers produce.
On the 6300's front panel, the total loudness controller gain reduction is
shown in blue on the L
We included this safety limiter for customers whose policies require the
BS.1770 loudness meter reading to be constrained below a specified
threshold regardless of how loud human listeners perceive the program
to be. Our experience suggests that the BS.1770-2 meter will often over-
read material with unusually low peak-to-average ratios, like highly pro-
duced commercials and promos. Strict reliance on the BS.1770 meter can
therefore make such material sound unnaturally quiet compared to sur-
rounding material, so we prefer the sound when the CBS Loudness Con-
troller is used exclusively for loudness control.
For a more detailed discussion of this issue, refer to Using the ITU BS.1770
and CBS Loudness Meters to Measure Loudness Controller Performance,
starting on page 3-79.
The 6300's 2-band algorithm can be set to be phase-linear. We believe that this is the
ideal processing for classical music and jazz programming because it does not dy-
namically re-equalize high frequencies; the subtle HF limiter only acts to reduce high
frequency energy when it would otherwise cause overload because of the TV pre-
emphasis curve. The 6300's 2-band phase-linear structure therefore keeps the musi-
cal spectrum coherent and natural.
When using the AGC+L
typically 25 ms—about three-quarters of an NTSC frame. To make intelligent deci-
sions about how to process, the 6300 needs to look ahead at the next part of the
program waveform. As digital transmission processing advances further and further
from its analog roots, this is the inevitable price of progress.
To avoid lip sync problems in sound-for-picture applications, the 6300 allows you to
pad the delay to one full frame of 24, 25, or 29.97 fps video, which makes matching
audio and video delays convenient. See step 23 on page 2-19.
You can configure any of the 6300's outputs to supply a low-delay monitor signal to
drive talent headphones only, which is useful if talent monitors off-air through
headphones. (See step 10 on page 2-14.)
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