TC Electronic LM2 Plug-in - Manual (Page 12)

12 / LM6 Radar Loudness Meter
The Loudness Range descriptor quantifies the variation of the loudness measurement
of a program. It is based on the statistical distribution of loudness within a program,
thereby excluding the extremes. Thus, for example, a single gunshot is not able to
bias the LRA number.
EBU R128 does not specify a maximum permitted LRA. R128 does, however,
strongly encourage the use of LRA to determine if dynamic treatment of an audio
signal is needed and to match the signal with the requirements of a particular
transmission channel or platform.
Consequently, if a program has LRA measured at 10 LU, you would need to move
the master fader +- 5 dB to make loudness stay generally the same over the duration
of the program. (Not that you would want that).
In production, Loudness Range may serve as a guide to how well balancing has
been performed, and if too much or too little compression has been applied. If a
journalist or video editor isn’t capable of arriving at a suitable LRA, he could be
instructed to call an audio expert for help.
This may be regarded as initial production guidelines:
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 suitable for broadcast without further processing. LRA is even a fingerprint
of a program and stays the same downstream of production if no dynamics
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
measuring LRA.
Prog. Loudn.
Program Loudness/LKFS returns one loudness number for an entire program, film
or music track. Its unit is LUFS. Some vendors and countries use the unit “LKFS” or
“LUFS”, but they are identical: An absolute measure of loudness in the digital domain,
where the region around “0” is overly loud and not relevant for measuring anything
but test signals. Expect readings of broadcast programs in the range between -28
and -20 LUFS.
Program Loudness is used as a production guideline, for transparent normalizing of
programs and commercials, and to set loudness meta-data in delivery if so required.
For delivery or transmission of AC3 format, the meta-data 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