Short for “coder/decoder,” a codec is essentially an algo-rithm for encoding (and compressing) a stream of data for transmission, and then decoding and decompressing it at the receiving end. Usually the data involved represents audio or video content (see streaming). Typically the data is being downloaded from a Web site to be played on a personal computer or portable player (see multimedia and music and video players, digital).
A codec is described as “lossy” if some of the origi-nal information is lost in the compression process. It then becomes a question of whether the loss in quality is per-ceived by the user as significant. A codec that preserves all the information needed to re-create the original file is “loss-less.” For most purposes, the much greater size of the loss-less version of a file is not worth the (often imperceptible) increase in quality or fidelity.
A codec is usually used in connection with a “container format” that specifies how the encoded data is to be stored
Codec Container Description
AAC advanced audio coding; developed as a
successor to MP3 and especially used
by Apple (iTunes, iPod, iPhone, etc.)
AIFF audio interchange file format; audio
container format for transferring content
between applications
ALAC Apple lossless audio codec
AVI audio video interleave; video and movies
container format
FLACC free lossless audio codec; music, open
source, lossless
MP3 actually MPEG-3, probably the most
common music codec
MPEG Moving Picture Experts Group; video,
movies, audio (four layers MPEG-1
through MPEG-4)
Ogg Vorbis music, open source (often used on Linux
systems)
Quick Time Apple multimedia
Real Audio and developed by RealNetworks for many
and RealVideo platforms
RIFF resource interchange file format; container
format
Vorbis free, open-source audio codec (often used
in Linux)
WAV Windows audio format (usually
uncompressed)
WMA Windows media audio
WMV Windows media video
in a file. Often a container can hold more than one data stream and even more than one kind of media (such as video and audio). When one refers to a Windows WAV file, for example, one is actually referring to a container.
Most of the popular codecs and file formats are propri-etary, which creates something of a dilemma for users who prefer open-source solutions. However, while most Linux distributions do not include support for formats such as MP3 out of the box, distributions such as Ubuntu are now making it easier for users to choose nonsupported propri-etary codecs if desired.
The preceding table lists some codecs likely to be encountered by program developers and consumers.
A codec is described as “lossy” if some of the origi-nal information is lost in the compression process. It then becomes a question of whether the loss in quality is per-ceived by the user as significant. A codec that preserves all the information needed to re-create the original file is “loss-less.” For most purposes, the much greater size of the loss-less version of a file is not worth the (often imperceptible) increase in quality or fidelity.
A codec is usually used in connection with a “container format” that specifies how the encoded data is to be stored
Codec Container Description
AAC advanced audio coding; developed as a
successor to MP3 and especially used
by Apple (iTunes, iPod, iPhone, etc.)
AIFF audio interchange file format; audio
container format for transferring content
between applications
ALAC Apple lossless audio codec
AVI audio video interleave; video and movies
container format
FLACC free lossless audio codec; music, open
source, lossless
MP3 actually MPEG-3, probably the most
common music codec
MPEG Moving Picture Experts Group; video,
movies, audio (four layers MPEG-1
through MPEG-4)
Ogg Vorbis music, open source (often used on Linux
systems)
Quick Time Apple multimedia
Real Audio and developed by RealNetworks for many
and RealVideo platforms
RIFF resource interchange file format; container
format
Vorbis free, open-source audio codec (often used
in Linux)
WAV Windows audio format (usually
uncompressed)
WMA Windows media audio
WMV Windows media video
in a file. Often a container can hold more than one data stream and even more than one kind of media (such as video and audio). When one refers to a Windows WAV file, for example, one is actually referring to a container.
Most of the popular codecs and file formats are propri-etary, which creates something of a dilemma for users who prefer open-source solutions. However, while most Linux distributions do not include support for formats such as MP3 out of the box, distributions such as Ubuntu are now making it easier for users to choose nonsupported propri-etary codecs if desired.
The preceding table lists some codecs likely to be encountered by program developers and consumers.
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