Audio Codecs in a Nutshell
Uncompressed digital audio files can take up a huge amount of space on your
computer's hard drive. CD-quality audio requires approximately 10MB of storage
space for each minute. Fortunately, there are many compression schemes for
reducing the size of audio files. These audio codecs (compression /
decompression) can provide good sounding audio at a fraction of the space
required by uncompressed audio.
An audio codec is a computer program that is used both to create a certain
format of audio file and to play it back. The same or compatible codec that is
used to compress the audio must be installed on the computer in order to listen
to the file. For example, you cannot listen to MP3 files without having an MP3
codec installed in your computer.
There are two basic types of audio codecs - lossless and lossy. Lossless codecs
retain all the original data of the original sound file while lossy codecs
remove some of the data. Loss the schemes provide for greater compression and
smaller file sizes but there is no way to restore the audio to its original
quality. Lossless codecs allow you to restore the audio.
There is a great variety of audio codecs because some are more suitable for
certain kinds of audio. For example, some codecs are ideal for speech and others
are better for music. In choosing a codec, you want the resulting file to retain
good sound quality while reducing the file size as much as possible.
Without a doubt, the most popular codec is MP3. It is suitable for all types of
audio files and can be used to encode audio at a great variety of bit rates. The
most common bit rate for music is 128 (kbps) kilobytes per second, which
provides a compression rate of about 10/1. This means you can store the music
from 10 CDs into the space equivalent to one CD. The popularity of MP3 audio
codecs has greatly enhanced the ability to distribute music over the Internet.
Audio codecs designed for compressing voice files are widely used in mobile
communication devices like cellular phones. The limited frequency range of the
human voice allows voice files to be compressed to a fraction of their original
size allowing them to be instantly transmitted through digital networks.
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