Telos Alliance LINEAR ACOUSTIC ARC, Installation & User Manual

Page: 50 / 72

Chapter 7 |
40
An Introduction to APTO™
What Makes APTO Different?
Traditional real-time television processing normally employs a series of wideband and/or multiband compressors or AGCs that
react to changing input levels by either increasing or decreasing gain in an effort to provide a more consistent output level. The
various threshold, ratio, and attack and release rates can be adjusted to help determine the amount of dynamic range present
at the output, or, put another way, how close to the desired output level the audio remains at any given time. A final look-ahead
limiter is typically employed for peak control.
One potential downside to this type of processing is that unless the audio falls below a specified gate threshold – the point at
which low level audio isn’t increased so as not to bring up background noise – the gain is always changing, whether it needs to
or not. Furthermore, multiband processing by design re-balances the spectral mix of the program. This can be advantageous
for helping to fix less-than-ideal mixes or if a spectrally consistent output is a priority, but it can also affect the artistic intent of
well-mixed content.
In contrast, APTO focuses on achieving the following goals:
♦
Ensuring that foreground sounds – particularly dialog – remain intelligible at all times
♦
Allowing the user to define a comfort zone within which no additional audio processing is applied, providing a more
natural sense of dynamics
♦
Maintaining the spectral balance of the original program material to preserve artistic intent
♦
Achieving and maintaining an output target level that is in compliance with global loudness regulations and is
optimized for distribution platforms (such as streaming and on-demand services) and for specific devices and listening
environments (including mobile phones and tablets)
How Does APTO Work?
In very basic terms, APTO first measures and analyzes the loudness of the incoming audio. In its first processing stage – the
“Dynamic Range” stage - it applies realtime loudness control to reduce the overall dynamic range and get the levels within the
user-defined comfort zone. This processed audio is then scaled in the second processing stage – the “Compliance” stage - to
achieve an average output level that matches the desired target loudness value.
As mentioned previously, ARC includes a host of factory profiles for various loudness standards and deliverable platforms, but
individual controls to fine tune both processing stages are also brought out to the user interface and are described in greater
detail later in Chapters 8 and 9.