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lM6
based level jumps are currently creating havoc in digital
TV, and LM6 helps correct that situation. The LM6
Loudness Meter can be used to control level and improve
sound, not only in Dolby AC3 based transmissions, but
also on other broadcast platforms, such as analog TV,
mobile TV and IPTV.
To summarize: LM6 is part of a holistic and universal
approach to loudness control, starting at the production
or live engineer. When she realizes the dynamic range
at her disposal, less processing is needed at later stages
of a distribution chain. The chain ends with the capability
of quality controlling everything upstream by applying the
same loudness measure for logging purposes: A closed
loop.
Welcome to a new, standardized world of audio leveling.
Across genres, across formats, across the globe.
Display
LM6 may use either the measurement unit of LU (Loudness
Units) or LUFS (Loudness Units Full Scale). LU and LUFS
are measurements in dB, reflecting the estimated gain
offset to arrive at a certain Reference Loudness (LU) or
Maximum Loudness (LUFS) as defined in BS.1770. Since
a common reference point for LU has not been agreed on
at the time of writing, LUFS (or “LKFS”, pointing specifically
to the Leq(R2LB) weighting of BS.1770), might be favored
initially to avoid ambiguous use of the term LU.
The effectiveness of any loudness meter depends on
both the graphical appearance and dynamic behavior
of its display, as well as on its underlying measurement
algorithms. A short-term loudness meter also relies on
the measurement algorithm’s ability to output pertinent
loudness information using different analysis windows,
for instance, 200-800 ms for running realtime updates.
It should be noted how the optimum size of this window
varies from study to study, possibly because the objective
of a running display hasn’t been fully agreed upon.
Formal evaluation of a visualization system is challenging:
First of all, one or more metrics must be defined by which
the display should be evaluated. The correspondence
between the sound heard and the picture seen is one
aspect to be evaluated. Another metric could characterize
the speed of reading the meter reliably.
In TC Electronic LM2, LM5 and LM6, short-term, mid-term
and long-term of loudness measurements are tied together
coherently, and displayed in novel ways (angular reading
and radar) that were preferred in its development and
test phases. However, we remain open to suggestions for
further improvement of the visualization of loudness.
Post Script
Control of loudness is the only audio issue that has made It
to the political agenda. Political regulation is currently being
put into effect in Europe to prevent hearing damage and
disturbances from PA systems, and to avoid annoying level
jumps during commercial breaks in television. In Australia,
something similar may happen.
Many years of research into loudness of not only
dialog, but also of loudness relating to any type of audio
programming, has brought TC to the forefront of companies
in the world to perform realtime loudness measurement
and control. Therefore, TC has taken active part in
loudness standardization efforts in Japan, the United
States, Europe and other areas.
In broadcast, digitization is driving the number of AV
channels and platforms up, while the total number
of viewers remains roughly the same. On the sound
production side, it is therefore important that delivery
criteria can be easily specified and met, even by people
not primarily concerned with audio: Journalists, musicians,
video editors, marketing professionals etc.
Using only dialog based audio measurements in digital
broadcast, has led to ambiguous level management, more
level jumps between programs, and extra time spent on
audio production and management in general. Non-dialog
