Perceived Quality in Game Audio - Game Sound Technology and Player Interaction: Concepts and Developments - page 154

content presentation. Therefore, the audio has
to be manipulated in real-time depending on the
player's actions. Real-time processing of audio
can become computationally very demanding
and is a problem for complex game scenarios.
This has introduced the concept of plausibility:
the main goal in game audio is not to have an
audio simulation as exact and close to reality as
possible, but to render audio that is plausible in
the game scenario, and that provides an overall
quality impression that matches the other aspects
of the game.
One fact well known from home cinema ap-
plications is that an improved quality in video
can also increase the subjectively perceived audio
quality, and that the reverse effect also exists
(Beerends & De Caluwe, 1999). It is therefore a
most interesting question to see whether these ef-
fects can be exploited to increase the subjectively
perceived overall quality of a game without actu-
ally increasing the computational load. Instead of
just rendering more details (equivalent to a higher
simulation depth), focusing on those details that are
actually relevant in a certain context could provide
a much higher Quality of Experience (QoE) (see
Farnell, 2011 for a discussion of relevancy and
redundancy in procedural audio design).
The central question is, therefore, which stimuli
in a game scenario are of most importance? Can
information that is difficult and cost-intensive to
convey in one modality be presented in another
modality with less effort but similar perceptual
impact? What role does interactivity play in
the perception of quality? What are the techni-
cal parameters that can influence the perceived
quality of a game, and which other factors exist
that potentially dominate the perceptual process?
This chapter aims at identifying and discussing
general quality criteria in multimedia application
systems with a focus on games. These criteria
contain technical as well as human factors. In
order to understand these factors, the first section
touches upon the mechanisms of human percep-

tion: well-known facts about visual and auditory
perception are summarized briefly.
The second section presents a discussion of
cross-modal influences, that is, interaction be-
tween auditory and visual stimuli in the perceptual
apparatus, and cross-modality in general. A survey
detailing the most accepted theories of how audio-
visual (bimodal) perception is achieved in the
human brain is given. This is far more complex
than just adding the results of auditory and visual
processing and is therefore worth an extended
discussion. This is followed by examples of ef-
fects in bimodal perception (based on research in
the fields of psychology and cognitive sciences)
that can be relevant in the context of game audio.
The third section discusses the concept of
auditory and audio-visual plausibility. It briefly
compares the requirements for exact (room)
acoustic simulations versus real-time rendering
and details the constraints resulting for computer
games.
The next section gives an overview on issues
related to interactivity, such as latency, user input,
and perceptual feedback. Interactivity is closely
related to the generation of presence, defined as
the “perceptual illusion of non-mediation”, or
simply the feeling of “being there”. The concept
of presence is discussed as an indirect measure
for perceived quality.
The fifth section elaborates on the concept
of attention. The perception of multiple streams
is discussed and an introduction to the general
model of the Perceptual Cycle according to Neis-
ser is given. From this, the concepts of selective
attention and divided attention are discussed and
capacity limits of the human perceptual system
are explained.
Finally, in the sixth section, the resulting factors
(technical as well as human) are arranged to form
a qualitative model describing human audio-visual
perception based on saliency of stimuli. Such a
model can serve as a basis for determining the
QoE in games in general and specifically for game
audio. Experimental results documenting inner-