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LM6
English Manual (2014-03-05) 55
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
Before a new measurement, click the Reset but-
ton. This will reset the descriptors, the radar and
the true-peak meters.
Run the audio, and watch the Radar and the de-
scriptor fields update accordingly.
While the Radar will update instantly, the de-
scriptors will wait five seconds into the program
before showing the first readings. This is normal.
Even though the first five seconds of a program
are not shown instantly, they are included in the
descriptor calculations.
LM6 incorporates an intelligent gate which dis-
criminates between foreground and background
material of a program. Consequently, measuring
won’t start before audio has been identified. The
intelligent gate also pauses measurements dur-
ing periods that only contain background noise,
and during fade-outs of music tracks.
Universal Descriptors
and Dolby LM100
Unlike methods that measure dialog only, LM6
may be used with any type of audio, including
dialog.
If you wish to measure dialog, it is recommended
to do a manual spot check of a program or a film.
Find 10-30 seconds of regular dialog and mea-
sure it with LM6. Where dialog may be soft, reg-
ular or loud, and shift by more than 15 dB inside
a film, regular dialog tends to be less ambiguous
and more consistent 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
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 read-
ings 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
rely on this parameter may take place in the con-
sumer’s receiver. Therefore, its value should not
be far off target, or the consumer results become
highly unpredictable.
Program Loudness in LM6 is directly compatible
with dialnorm in AC3. Most broadcast stations
work with a fixed dialnorm setting, for instance
-23 LUFS. This would be the Program Loudness
target level for any program.
If your station is more music- than speech-ori-
ented, better inter-channel leveling may be ob-
tained with dialnorm permanently set 1 or 2 LU
below the Program Loudness target level.
True-peak meters
The peak meters of LM6 display true-peak as
specified in ITU-R BS.1770. True-peak meters
give a better indication of headroom and risk
of distortion in downstream equipment such as
sample rate converters, data reduction systems
and consumer electronics than digital sample
meters used e.g. in CD mastering. Note that the
standard level meters in most digital worksta-
tions and mixers are only sample peak (Final Cut,
Avid, ProTools, Yamaha etc.) and should only be
used as a rough headroom guideline.
Note that the meter scale is extended above
0 dBFS. Most consumer equipment distorts if
you see readings above 0. It’s not a problem to
have true-peak level going to -1 dBFS in produc-
tion, but legacy platforms (analog, NICAM etc.)
and some data-reduction codecs may distort
unless true-peak level is kept lower.