Media Audio (WMA) is a proprietary compressed audio file
format developed by Microsoft. It was initially intended
to be a competitor to the popular MP3 format, though in
terms of popularity of WMA files versus mp3 files, this
never came close to occuring. With the introduction of
Apple's iTunes Music Store, WMA has positioned itself
as a competitor to the Advanced Audio Coding format used
by Apple and is part of Microsoft's Windows Media framework.
large number of consumer devices, ranging from portable
hand-held music players and handphones to set-top DVD
players, support the playback of WMA files. WMA is second
only to MP3 in popularity in terms of number of devices
initial reason for the development of WMA may have been
that MP3 technology is patented and has to be licensed
from Thomson SA for inclusion in the Microsoft Windows
is capable of VBR, CBR and lossless audio encoding in
order to be marketed as a versatile format.
Media Audio can optionally support digital rights management
using a combination of elliptic curve cryptography key
exchange, DES block cipher, a custom block cipher, RC4
stream cipher and the SHA-1 hashing function.
WMA file is often encapsulated in an Advanced Systems
Format (ASF) file. The resulting file may have the extension
"wma" or "asf" with the "wma"
extension being used only if the file is strictly audio.
The ASF file format specifies how metadata about the file
is to be encoded, akin to the ID3 tags used by MP3 files.
began being widely distributed starting with the WMA 7
lossy compression based codec and has now reached version
9. Microsoft's WMA bundle also includes three more codecs,
a Windows Media Audio 9 Voice codec, Windows Media Audio
9 Lossless codec and Windows Media Audio 10 Professional
codec (earlier known as WMA 9 Pro). The WMA 10 Pro codec
is based on a completely different technology (superior
to "ordinary" WMA in terms of quality and features)
and thus WMA 10 Pro files are incompatible with older
players. WMA 10 Pro supports 96 KHz 24-bit audio as well
as 5.1/7.1 multi-channel audio.
Media Player 11 is the latest version of Microsoft's media
player, more information here
from Windows Media Player, WMA files can be played using
MPlayer, Winamp (with certain limitations — DSP
plugin support and DirectSound output is disabled using
the default WMA plugin), RealPlayer, and many other media
players. The FFmpeg project has reverse-engineered and
reimplemented the WMA format to allow its use on POSIX
compliant operating systems such as Linux, and RealNetworks
has announced plans to support playing non-DRMed WMA files
in RealPlayer for Linux.
November 2005, a new update was available for the PlayStation
Portable (version 2.60) which allowed WMA files to be
played on the console for the first time.
Microsoft claimed that files in WMA format sounded better
than MP3 files at the same bitrate; Microsoft also claimed
that WMA files sounded better than MP3 files at higher
bitrates. However, double blind listening tests with other
lossy audio codecs have consistently failed to support
Microsoft's claims about its superior quality. Indeed,
the first independent test (2004/05) with WMA standard
encoder provided by the Windows Media 9, conducted at
128 kb/s, showed that WMA was roughly equivalent to MP3
encoded with LAME encoder, inferior to AAC and Vorbis,
and superior to ATRAC3 (software version).
conclusions made by recent listening tests:
At 128kb/s the most recent large scale test (2006/01)
shows a four way tie between aoTuV Vorbis, LAME-encoded
MP3, WMA Pro and iTunes (QuickTime) AAC, with each codec
essentially transparent (sounds identical to the original
music file). However, device and player support for WMA
Pro is not as prevalent as WMA Standard. Generally speaking,
WMA (without any other qualifiers) refers to the WMA Standard.
At mid-low bitrates (64 kb/s or more, less than 128 kb/s),
latest private tests (80 kb/s (2005/07), 96 kb/s) (2005/08)
show that WMA has a lower quality than the lossy audio
codecs AAC (HE and LC) and Vorbis, a roughly equivalent
quality than MP3, and a better quality than MPC. However,
it must be remembered that these tests are only individual
tests and not collective tests.
At low bitrates (less than 64 kb/s), a collective independent
test targetting 32kb/s (2004/07) demonstrated that WMA
is clearly superior to MP3 (produced by LAME), but not
better than modern competitive lossy formats.
of these results, however, are difficult to keep up-to-date
due to the ever-evolving nature of the codecs.
the Windows Media Audio codec itself does not contain
any digital rights management facilities, the Advanced
Systems Format (ASF) container format, in which a WMA
stream may be encapsulated, can. Janus is the codename
for a recent version of Windows Media DRM, which is sometimes
used in conjunction with WMA. The DRM technology supports
time-limited music such as those offered by unlimited
download services, such as Napster,Yahoo! Music Unlimited
and Virgin Digital. Janus DRM is incompatible with most
portable audio devices since they typically support up
to WMA DRM Version 9. CD tracks ripped with Windows Media
Player are "protected" (DRM-restricted) by default,
though this setting can be changed.