Game Development Reference
In-Depth Information
But as much as it can add to the gaming experience, the reality is that a large per-
centage of players will not have a 5.1 surround configuration. Because of this, it
is not really viable to create a game that relies on surround sound to function. Al-
though it certainly will sound better on a $1000 home theater setup, the game still
has to work on tinny built-in TV speakers or a bad pair of headphones.
Although you can't separate front and back in a stereo configuration, this does not
mean that the game still can't support positional sounds. The positions of both the
listener and the emitters, as well as the falloffs and other parameters, will still af-
fect the volume and left/right placement of the sound.
Digital Signal Processing
In a broad sense,
digital signal processing
(DSP) is the computational manipu-
lation of a signal. In the realm of audio, DSP typically refers to taking a sound
source file and modifying it on playback to sound differently. A relatively simple
DSP effect would be to take a sound and increase or decrease its pitch.
It might seem like there would be no need to perform DSP effects on the fly, and
rather bake such effects into the sound files that the game engine plays back. But
the reason a runtime DSP effect is useful is because it can save a great deal of
memory. Suppose that in a sword-fighting game, there are 20 different sound ef-
fects for swords clanging against each other. These sound effects were authored
so they sound roughly like they are clanging in a wide open field. Now imagine
that the game has a wide variety of locales where the sword fights can occur, in
addition to the open field—it can be in a small cave, a large cathedral, and a great
deal of other places.
The problem is that swords clanging in a small cave are going to sound dramat-
ically different than in an open field. Specifically, when swords clang in a small
cave, there is going to be a great deal of echo, or
reverb
. Without DSP effects, the
onlyrecoursewouldbetoauthorasetofthose20sword-clangingsoundsforevery
single locale. If there's five such distinct locales, that means a fivefold increase,
to a total of 100 sword-clanging sounds. Now if this is the case for all the combat
sounds, not just the sword ones, the game may very quickly run out of memory.
But if DSP effects are available, the same 20 sword-clanging sounds can be used
everywhere; they just have to be modified by the effects to create the desired end
result.
To actually implement DSP effects requires knowledge of linear systems and ad-
vancedmathematical operationssuchastheFouriertransform.Becauseofthis,the
