file formats exist for recording and playing digital
sound and music files. While many of these file formats are software
dependant for example a Creative Labs Music File is a .cmf there
are several well-known and widely supported file formats. While
operating systems have different popular music file
formats, we'll mainly focus on those that are most commonly used on
Many different digital audio formats and different software
are used to create, store and manipulate these files, the
good news for consumers is that there is also a wide range of
devices and products available that support multiple formats.
Should you not have the correct device for playing a particular file, you can also look
for software conversion tools that will convert one file type to
another. Because some audio files are open standards and some are
proprietary, chances are we'll be seeing a wide variety of digital
audio formats for some time to come.
File Format and Codec
An audio file format and audio codec (compressor/decompressor)
are two very different things. Audio codecs are the
that are executed in multimedia players. The audio codec is
actually a computer program that compresses or decompresses digital
audio data according to the audio file format specifications. For
example, the WAV audio file format is usually coded in the OCM
format, as are the popular Macintosh
AIFF audio files.
Audio Formats can be broken down into three main categories.
compression formats, and lossy
Key Terms To
Understanding Digital Audio Formats
Refers to the reproduction and transmission of sound stored in a
digital format. This includes CDs as well as any sound files stored
on a computer.
Storing data in a format that requires less space than usual.
Refers to data compression techniques in which no data is lost.
Refers to data compression techniques in which some amount of data
is lost. Lossy compression technologies attempt to eliminate
redundant or unnecessary information.
formats (often referred to as PCM formats) are just as the name
suggests formats that use no compression. This means all the data is
available, at the risk of large file sizes. A WAV audio file is an
example of an uncompressed audio file.
applies compression to an uncompressed audio file, but it doesn;t lose
information or degrade the quality of the digital audio file. The WMA
audio file format uses lossless compression.
will result in some loss of data as the compression algorithm eliminates
redundant or unnecessary information basically it tosses what it sees
as irrelevant information. Lossy compression has become popular online
because of its small file size, it is easier to transmit over the
Internet. MP3 and Real Audio files uses a lossy compression.
Common Windows-compatible Audio Formats
MP3 is the name of the file extension and also the name of the type of file for
MPEG, audio layer 3. Layer 3 is one of three coding schemes (layer 1,
layer 2 and layer 3) for the compression of audio signals. Layer 3 uses
perceptual audio coding and psychoacoustic compression to remove all
superfluous information (more specifically, the redundant and irrelevant
parts of a sound signal. The stuff the human ear doesn't hear anyway).
It also adds a MDCT (Modified Discrete Cosine Transform) that implements
a filter bank, increasing the frequency resolution 18 times higher than
that of layer 2. The result in real terms is layer 3 shrinks the
original sound data from a CD (with a bit rate of 1411.2 kilobits per
one second of stereo music) by a factor of 12 (down to 112-128kbps)
without sacrificing sound quality.
WMA - Windows Media Audio (.wma)
Short for Windows Media Audio,
WMA is a Microsoft file format for encoding
digital audio files similar to MP3 though can compress files at a higher
rate than MP3. WMA files, which use the ".wma" file extension, can be of
any size compressed to match many different connection speeds, or
WAV is the format
used for storing sound in files developed jointly by Microsoft and
IBM. Support for WAV files was built into Windows 95 making it the de
facto standard for sound on PCs. WAV sound files end with a .wav
extension and can be played by nearly all Windows applications that
Real Audio (.ra .ram .rm)
Real Audio is a proprietary format, and is used for streaming audio
that enables you to play digital audio files in real-time. To use this
type of file you must have RealPlayer (for Windows or Mac), which you can
download for free. Real Audio was developed by RealNetworks.
MIDI - Musical Instrument
Digital Interface (.mid)
Short for musical instrument digital interface,
MIDI is a
standard adopted by the electronic music industry for controlling
devices, such as synthesizers and sound cards, that emit music. At
minimum, a MIDI representation of a sound includes values for the note's
pitch, length, and volume. It can also include additional
characteristics, such as attack and delay time.
Ogg is an
audio compression format, comparable to other formats used to store and
play digital music, but differs in that it is free, open and unpatented.
It uses Vorbis, a specific audio compression scheme that's designed to
be contained in Ogg.
Converting Audio Formats
With a slew of software applications available today, consumers can
convert one digital audio file format to virtually any other. many of the
programs available today offer standard burning or converting tools to
enable consumers to create CDs on their computer which can be played in home
or car stereos. Usually these tools will convert or burn uncompressed WAV
PCM, compressed WAV , MP3, and Ogg Vorbis.
Did You Know...
Marketing firm iSuppli predicts that total MP3 player shipments
will expand to 132 million units in 2009, rising at a compound
annual growth rate (CAGR) of 29.1% from 36.8 million in 2004.
Vangie 'Aurora' Beal
Last updated: September 30, 2005
"Did You Know...?" When Is Downloading Music on the Internet Illegal
For many people it is as simple as opening one of many peer-to-peer file share
programs, selecting the tracks, downloading and burning to a CD-ROM. What isn't
so simple about downloading music is the copyright protection laws that people
break everyday by downloading some music tracks off the Internet.
MP3 AND AAC EXPLAINED (PDF)
The last years have shown widespread proliferation of .mp3-files, both from
legal and illegal sources. Yet most people using these audio files do not know
much about audio compression and how to use it. The paper gives an introduction
to audio compression for music file exchange. Beyond the basics the focus is on
quality issues and the compression ratio / audio bandwidth / artifacts
Digital Audio Formats
Digital audio comes in many different formats, and multiple formats will be a
fact of life for the foreseeable future. Groups like MPEG have created open
standards, but even formats based on the same MPEG standard may not compatible
with each other because of proprietary components.
Audio & MP3 Downloads
Find free and trial versions of music & sound editors, encoders, plug-ins, and
An overview of digital audio file formats and codecs.
Audio Preservation Handbook (PDF)
Sound in its original state is a series of air vibrations (compressions and
rarefactions), which are captured by our ears and then converted to electronic
impulses for interpretation.
Mix, burn, or play every major media format.