About target lkfs value, Appendix a – Cobalt Digital COMPASS 9086 Embedded Audio Loudness Processor User Manual
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Appendix A
About Target LKFS Value
A-2
9086-SD PRODUCT MANUAL
9086-OM (V4.3)
About Target LKFS Value
(See Figure A-1.) Adherence to a target LKFS value across various program
material (typically from any number of individual, diverse sources) relieves
viewers from having to constantly adjust program volume at their homes in
order to maintain an overall comfortable, desired loudness level. General
guidelines for determining a target LKFS value are as follows:
•
Unless specified by a metadata dialnorm value or some other
specified guidance, target LKFS should be at or about -27 ±2.0 LKFS
(that of the typical dialnorm value) across any portion of program
material containing any appreciable audio content (anything other
than dramatically or aesthetically intentional silence).
•
Because the LKFS unit of measure is directly derived from the
decibel, a gain change of a given amount modifies measured LKFS
by the same amount. For example, material exhibiting an LKFS of
-12 LKFS can be made to match that of material exhibiting a
-24 LKFS level by reducing the overall level at the source by 12 dB.
•
Where local content is to be added to a network-supplied feed (e.g.,
local commercial or programming announcements), care should be
taken that the LKFS level of local content matches that specified by
the metadata dialnorm.
•
Dynamic Range Control (DRC) control/management systems by
themselves cannot unconditionally be relied upon to assure proper
LKFS compliance. Many DRC systems use measurement/control
schemes that do not reflect perceived loudness. A system specified to
use energy measurement/assessment models reflecting perceived
loudness, such as the Cobalt
®
loudness processing used by this card
(AEROMAX™ licensed from Linear Acoustic™), can reliably
provide DRC to achieve LKFS compliance.
Figure A-1 shows an example of measuring LKFS for an ingest piece and
using the result to assess and remedy the loudness variation between the piece
and a dialnorm-specified network feed.