Algorithm Manual Revision 4

LM6
English Manual – Updated 2018-02-28 183
This may be regarded as initial production guide-
lines:
►
HDTV and digital radio: Stay below LRA of 20
LU.
►
SDTV: Stay below LRA of 12 LU.
►
Mobile TV and car radio: Stay below LRA of
8 LU.
Remember to use LRA the other way around
too: If there is an ideal for a certain genre, check
its LRA measure, and don’t try go below it. LRA
should not be used for Limbo. Allow programs or
music tracks the loudness range they need, but
not more than they need.
Loudness Range may also be measured on a
broadcast server to predict if a program is suit-
able for broadcast without further processing.
LRA is even a fingerprint of a program and stays
the same downstream of production if no dy-
namics processing has been applied. You may
even check the number out of a consumer’s set-
top box to verify that distribution processing and
Dolby DRC has been disabled.
Like with Program Loudness and Loudness
Max, the meter should be reset before measur-
ing LRA.
Prog. Loudn.
Program Loudness returns one loudness num-
ber for an entire program, film or music track. Its
unit is LUFS. Some vendors and countries use
the unit “LKFS” or “LUFS”, but all three are the
same: An absolute measure of loudness in the
digital domain, where the region around “0” is
overly loud and not relevant for measuring any-
thing but test signals. Expect readings of broad-
cast programs in the range between -28 and -20
LUFS.
Program Loudness is used as a production
guideline, for transparent normalizing of pro-
grams and commercials, and to set loudness
metadata in delivery if so required. For delivery
or transmission of AC3 format, the metadata
parameter “dialnorm” should reflect Program
Loudness. The easiest way to handle multiple
broadcast platforms is to normalize programs
at the station to a certain value, thereby being
able to take advantage of the normalization ben-
efits across platforms, at the same time enabling
static metadata.
Loudness measurements in LM6 are all rooted in
ITU-R BS.1770. However, subtle differences exist
between different regions of the world. Therefore
LM6 also includes the “Loudness Standard” pa-
rameter. Be sure to set this parameter correctly
for compliance in your region.
The Program Loudness target is more or less the
same for broadcasters around the world, espe-
cially when taking the measurement differences
into account. Target numbers range between -24
and -22 LUFS.
Like with Loudness Range and Loudness Max,
the meter should be reset before measuring Pro-
gram Loudness.
Sliding Loudn.
Sliding Loudness, unlike Program Loudness,
Loudness Range and Loudness Max, is a contin-
uously updated measure that doesn’t need to be
reset. This type of descriptor is especially useful
when “mixing by numbers”, i.e. when there is no
access to the extremely informative radar dis-
play. When mixing by numbers, having Program
Loudness as one descriptor and Sliding Loud-
ness as the other displays simultaneous informa-
tion about the full program side by side with the
most recent loudness history.
Note 1: Because the Sliding Loudness measure-
ment is completely un-gated, it may also be used
to spot check sections of a program complying
to “raw” ITU-R BS.1770 and the first revision of
ATSC A/85.
Note 2: LM6 makes use of optimized statistics
processing in order to display a sliding loudness
value (a prognosis) as quickly as possible after
a reset.
Loudness Max
Loudness Max displays the maximum loudness
registered since the meter was last reset. Loud-
ness Max is an especially useful parameter when
checking and normalizing short duration pro-
grams such as promos and commercials. BCAP
rules from the UK is an example of using Loud-
ness Max as an efficient instrument to reduce
listener complaints regarding loud commercials.
While Program Loudness is adequate to normal-
ize a consistent mix, Loudness Max may be used
as a second line of transparent defense against
overly short and loud event.