Algorithm Manual Revision 4

LM6
English Manual – Updated 2018-02-28 181
conditions etc using normal DB4 and DB8 preset
handling procedures.
Radar page
Current Loudness: Outer Ring
The outer ring of the Radar page displays Mo-
mentary loudness. The 0 LU point (i.e. Target
Loudness) is at 12 o’clock, and marked by the
border between green and yellow, while the Low
Level point is marked by the border between
green and blue. The “0 LU Equals” and “Low
Level Below” parameters are found on the Setup
page. For instance, if 0 LU is set at -22 LUFS,
and Low Level is set at -20 LU, the color coding
of Fig3 applies.
The user should be instructed to keep the outer
ring in the green area, and around 12 o’clock on
the average. Excursions into the blue or the yel-
low area should be balanced, and not only go in
one direction.
The numbers associated with the outer ring may
be referenced at either maximum loudness, or
have a zero point set set at Target Level. Choose
“LUFS” or “LU” at the Loudness Scale selection
on the Main page depending on your preference.
Either way of looking at loudness is valid. LUFS
reading is in line with how peak level is typically
measured in a digital system, and compatible
with Dolby
AC3 and E metadata, while the LU approach
calls for a certain Target Loudness to have been
predetermined, like e.g. a VU meter.
Long-term measurements
Universal descriptors may be used to make pro-
gram-duration measurements, or you may “spot-
check” regular dialog or individual scenes as re-
quired. It is recommended not to measure pro-
grams of a shorter duration than approximately
10 seconds, while the maximum duration may be
24 hours or longer.
Reset button
Reset button
Before a new measurement, press the Reset
button. This resets the descriptors, the radar and
the true-peak meters. Run the audio, and watch
the radar and descriptor fields update accord-
ingly. It is normal that the descriptors wait five
seconds into the program before showing the
first readings, while the radar updates instantly.
The first five seconds of a program are included
in the descriptor calculations, even though they
are not shown instantly.
LM6 incorporates an intelligent gate, which dis-
criminates between foreground and background
material of a program. Consequently, a measure
doesn’t start before audio has been identified. It
also pauses the measurement during periods of
only background noise, and in the fade-out of a
music track.
Universal Descriptors and Dolby LM100
Unlike methods that measure dialog only, LM6
may be used with any type of audio – which in-
cludes dialog, of course. If you wish to measure
dialog, it’s recommended to do a manual spot
check of a program or a film. Find 10 to 30 sec-
onds of regular dialog and measure it with LM6.
Where dialog may be soft, regular or loud, and
shift by more than 15dB inside a film, regular di-
alog tends to be less ambiguous and more con-
sistent across a program.
For compatibility with a proprietary measure
such as Dolby LM100, only some of these meters
are updated to use ITU-R BS.1770 and Leq(K)
while others are locked at Leq(A). The software
version of LM100 should be 1.3.1.5 or higher in
order for it to comply with BS.1770, and to have
its average loudness reading be compatible with
Center of Gravity in LM5 or Program Loudness
in LM6. Even used just on speech, Leq(A) is not
a precise approximation to perceived loudness,
so please update the unit to BS.1770 to obtain
similar readings and predictable results.
To measure dialog with LM6 the same way Dolby
LM100 is sometimes used, solo the Center chan-
nel during a spot check to momentarily disable
the channel weighting specified in BS.1770, if
you’re working on a 5.1 stem.
Universal Descriptors and AC3 Metadata
The “Dialnorm” parameter in AC3 metadata
should indicate the average loudness of a pro-
gram. Basic dynamic range and level control that