User Manual

iLM8 – Live User Manual
11
A long term loudness measurement of an entire clip is referred to as an infinite average. To achieve the
desired loudness level, this value can be used to update the Dial Norm metadata, thus affecting the
audio’s perceived loudness when processed at the point of consumption by way of the set top box or,
more recently, digital television receiver.
Granted that not all viewers will have equipment capable of processing metadata or Dial Norm
information, it is possible to control the perceived loudness by the application a fixed-offset to the audio
content after the infinite average of an entire piece of content has been measured. While this may
sound like the ideal loudness solution, it alone will never completely address loudness complaints.
For example, imagine that a movie starts with a dramatic scene
where the first ten minutes consist of speech and sound effects
measured at -31 LKFS. The second half of the scene includes a
car chase measuring at -17 LKFS. The Dial Norm correctly
describes the entire scene as -24 LKFS, however the viewer
perceives the audio level as very low for the first half of the clip
followed by audio that is significantly louder during the second
half. While this extreme dynamic range may be acceptable in a
movie theatre, it is typically not within the typical viewer’s home
environment. The infinite average and fixed-offset approach has
no way of addressing such intra-content issues.
Another challenge that fixed-offset correction cannot solve is how loudness is perceived in the context
of playback. In this scenario, a TV program ends quietly followed by a high-energy commercial. Even if
both pieces of content are properly prepared and played back at correct infinite average levels, an
abruptly louder start to the commercial will create a jarring effect when played back immediately after
the quiet ending.
Last century’s loudness solution was a fix-all audio processor that was situated at the end of the
broadcast chain, controlling loudness by ‘squashing’ the audio and removing essential audio dynamics.
With visual feedback presented from the iLM8 - Live, a new solution has emerged that enables
engineers to
measure perceived loudness correctly and take appropriate corrective action on the fly, imitating
methods used by audio mix engineers who actively ride their faders. When coupled with a proficient
listening ear, the solution is easily integrated with existing broadcasting workflows, delivering the
flexibility engineers need to adjust loudness levels in real-time, without removing any signal dynamics.