Game Development Reference
In-Depth Information
as multi-mono). Movie i les can have interleaving too—in this case the
video track is also considered a channel as well as the audio.
WAV
is the standard audio i le format used natively in Windows PCs for
uncompressed (PCM) sound i les.
AIFF
is a standard audio i le format used natively in Macintosh
computers for uncompressed (PCM) sound i les.
Open, Compressed Audio File Formats
Compressed formats take up less data space than uncompressed formats, but they lose audio quality
in the compression process (how much they lose depends on the bit rate of the compression). These
perceptually based formats take advantage of a limitation in human hearing called
auditory masking
.
This means that a lot of data existing outside of our perceptual limit can be removed from the sound
i le, thus saving space.
The format of compressed i les in general requires the presence of a
codec
(short for COmpression/
DECompression), a specialized piece of code that runs on software or hardware to decompress and
playback the i le. The encoder can process the i les at a constant rate of speed (constant bit rate, known
as CBR) or it can vary the rate depending on the complexity needed (variable bit rate, known as VBR). Be
aware that some hardware devices and audio engines may not support playback of VBR encoded i les.
MP3
(MPEG Layer 3) is currently the most popular format for downloading and storing music, and it is
also used in games. 'MP3 i les are compressed to roughly one-tenth the size of an equivalent PCM i le.'
MP3s can be compressed at a variety of bit and sample rates depending on the desired size and quality
of the i nal audio.
