File Types - A Practical Guide to Video and Audio Compression - page 681

I

File Types

I.1 File Types

Most operating systems distinguish between one file type and another by using a three-
or four-letter file extension. Mac OS Classic used a four-letter code for type and creator
properties, which were stored in the file metadata information. Both mechanisms are sup-
ported in Mac OS X. Windows uses file extensions to associate the file with an application,
while Linux- and UNIX-based systems delegate the file-type recognition to the application-
level software.
These file-mapping mechanisms are used by the operating system to run the appro-
priate application when the file is opened, although it is the shell or finder/explorer appli-
cation that arbitrates this.
Table I-1 summarizes file extensions and the owner, codec, or service that they are
associated with.

Table I-1 Video- and Audio-Related File Extensions

Extension Description

3GPP2 mobile phone video/audio

.3g2

3GPP mobile phone video/audio

.3gp

3GPP2 mobile phone video/audio

.3gp2

3GPP mobile phone video/audio

.3gpp

Advanced Authoring Format (used by MXF)

.aaf

QuickTime Audio Interchange File Format

.aif

QuickTime Audio Interchange File Format (compressed)

.aic

QuickTime Audio Interchange File Format (compressed)

.aifc

QuickTime Audio Interchange File Format

.aiff

AMC Media File

.amc

AMR Audio File

.amr

Windows Media Advanced Systems Format file

.asf

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