Windows Media Audio

WMAXMA.wmaWindows Media Audio LosslessWMA LosslessWindows Media Audio (WMA)Windows Media PlayerWMA ProWMA StandardWMA v10
Windows Media Audio (WMA) is the name of a series of audio codecs and their corresponding audio coding formats developed by Microsoft.wikipedia
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Windows Media Player

Windows Media Player MobileMedia PlayerWindows Media Player Mobile 10
Although earlier versions of Windows Media Player played WMA files, support for WMA file creation was not added until the seventh version.
The default file formats are Windows Media Video (WMV), Windows Media Audio (WMA), and Advanced Systems Format (ASF), and its own XML based playlist format called Windows Playlist (WPL).

Windows Media

WMFWindows Media SDKMicrosoft Windows Media framework
It is a proprietary technology that forms part of the Windows Media framework.
Windows Media Audio (WMA)

RealNetworks

Film.comRealRealNetworks, Inc.
RealNetworks also challenged Microsoft's claims regarding WMA's superior audio quality compared to RealAudio.
After some initial tries to push their own DRM scheme (named Helix DRM) onto all device manufacturers with the Creative Zen Xtra and the Sansa e200r as the only existing compliant devices, they sparked controversy by introducing a technology called Harmony that allowed their music to play on iPods as well as Microsoft Windows Media Audio DRM-equipped devices using a "wrapper" that would convert Helix DRM into the two other target DRM schemes.

Advanced Systems Format

ASF.asf.wma
Microsoft has also developed a digital container format called Advanced Systems Format to store audio encoded by WMA.
The most common media contained within an ASF file are Windows Media Audio (WMA) and Windows Media Video (WMV).

Rico Malvar

Henrique Malvar
The first WMA codec was based on earlier work by Henrique Malvar and his team which was transferred to the Windows Media team at Microsoft.
At Microsoft, Malvar contributed to the development of audio coding and digital rights management for the Windows Media Audio, Windows Media Video, and to image compression technologies, such as HD Photo / JPEG XR formats and the RemoteFX bitmap compression, as well as to a variety of tools for signal analysis and synthesis.

Audiophile

audiophilesaudio enthusiastaudiophile recordings
The former claim however was rejected by some audiophiles.
Audiophiles play music from a wide variety of sources including phonograph records, compact discs (CDs), and digital audio file formats that are uncompressed as well as ones that are compressed using lossless data compression such as FLAC, Windows Media Audio 9 Lossless and Apple Lossless (ALAC).

Digital container format

container formatcontainercontainer formats
Microsoft has also developed a digital container format called Advanced Systems Format to store audio encoded by WMA.
ASF (container for Microsoft WMA and WMV, which today usually do not use a container)

Variable bitrate

VBRvariable bit ratevariable
WMA 9 introduced variable bit rate (VBR) and average bit rate (ABR) coding techniques into the MS encoder although both were technically supported by the original format.
MP3, WMA and AAC audio files can optionally be encoded in VBR, while Opus, Vorbis are always in VBR.

Lossless compression

losslesslossless data compressioncompression
A lossless codec, WMA Lossless, compresses audio data without loss of audio fidelity (the regular WMA format is lossy).
WMA Lossless (Windows Media Lossless)

Gigabeat

Gigabeat SToshiba GigabeatGigabeat T-Series
Some notable exceptions to this are the Microsoft Zune (limited to stereo), Xbox 360, Windows Mobile-powered devices with Windows Media Player 10 Mobile, newer Toshiba Gigabeat and Motorola devices, and devices running recent versions of the Rockbox alternative firmware.
The hard drive player features capacities from 5 GB to 40 GB, support for MP3, WMA and WAV sound files, USB 2.0, and integration with Windows Media Player.

Microsoft PlaysForSure

PlaysForSurePlayForSureprotected
Certified PlaysForSure devices, as well as a large number of uncertified devices, ranging from portable hand-held music players to set-top DVD players, support the playback of WMA files.
The most commonly referenced requirements include the ability to play files encoded in Windows Media Audio or Windows Media Video format with Windows Media DRM digital rights management, used by Windows Media Player versions 10 and 11. For this, portable devices must implement Janus (WMDRM-PD), and network-attached devices must implement an interface to Cardea (WMDRM-ND).

Modified discrete cosine transform

MDCTMDCT-basedMDCTs
Fundamentally, WMA is a transform coder based on modified discrete cosine transform (MDCT), somewhat similar to AAC, Cook and Vorbis.
As a result of these advantages, the MDCT is employed in most modern lossy audio formats, including MP3, AC-3, Vorbis, Windows Media Audio, ATRAC, Cook, AAC, Opus, and LDAC.

Vorbis

Ogg VorbisOGGaoTuV
Fundamentally, WMA is a transform coder based on modified discrete cosine transform (MDCT), somewhat similar to AAC, Cook and Vorbis.
Vorbis had been shown to perform significantly better than many other lossy audio formats in the past in that it produced smaller files at equivalent or higher quality while retaining computational complexity comparable to other MDCT formats such as AAC or Windows Media Audio.

Digital rights management

DRMDRM-freedigital rights management (DRM)
This container can optionally support digital rights management (DRM) 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.
Napster music store offers a subscription-based approach to DRM alongside permanent purchases. Users of the subscription service can download and stream an unlimited amount of music transcoded to Windows Media Audio (WMA) while subscribed to the service. But when the subscription period lapses, all the downloaded music is unplayable until the user renews his or her subscription. Napster also charges users who wish to use the music on their portable device an additional $5 per month. In addition, Napster gives users the option of paying an additional $0.99 per track to burn it to CD or for the song to never expire. Music bought through Napster can be played on players carrying the Microsoft PlaysForSure logo (which, notably, do not include iPods or even Microsoft's own Zune). As of June 2009, Napster is offering DRM free MP3 music, which can be played on iPhones and iPods.

Psychoacoustics

psychoacousticpsychoacoustic modelpsychoacoustical
WMA is a lossy audio codec based on the study of psychoacoustics.
Some of these formats include Dolby Digital (AC-3), MP3, Opus, Ogg Vorbis, AAC, WMA, MPEG-1 Layer II (used for digital audio broadcasting in several countries) and ATRAC, the compression used in MiniDisc and some Walkman models.

Lossy compression

lossylossy data compressioncompressed
A lossless codec, WMA Lossless, compresses audio data without loss of audio fidelity (the regular WMA format is lossy).
WMA (Lossless codec available too)

RealAudio

RA.ram.ra
The original WMA codec, known simply as WMA, was conceived as a competitor to the popular MP3 and RealAudio codecs.
Windows Media Audio – Microsoft's media formats

Rockbox

Rockbox Project.rockRockbox kernel
Some notable exceptions to this are the Microsoft Zune (limited to stereo), Xbox 360, Windows Mobile-powered devices with Windows Media Player 10 Mobile, newer Toshiba Gigabeat and Motorola devices, and devices running recent versions of the Rockbox alternative firmware.
WMA Standard

FFmpeg

SnowlibavformatNUT
The format has never been publicly documented, although an open source decoder has been reverse engineered for non-Microsoft platforms by the libav and ffmpeg projects.

WMV HD

HD
In addition, WMA Pro is a requirement for the WMV HD certification program.
The soundtracks are commonly encoded using the Windows Media Audio Professional codec, often featuring 5.1 or 7.1 multichannel sound.

ID3

ID3 tagsID3v1.1tags
The ASF container format specifies how metadata about the file is to be encoded, similar to the ID3 tags used by MP3 files.
Windows media ASF files (WMA, WMV) have their own tagging formats but also support ID3 Tags embedded as attributes.

Data compression

compressionvideo compressioncompressed
In the same year, the bit stream syntax, or compression algorithm, was altered in minor ways and became WMA 2.
Newer ones include Free Lossless Audio Codec (FLAC), Apple's Apple Lossless (ALAC), MPEG-4 ALS, Microsoft's Windows Media Audio 9 Lossless (WMA Lossless), Monkey's Audio, TTA, and WavPack.

ISO base media file format

ISO BMFFbase media formatISO-based
Since 2008 Microsoft has also been using WMA Professional in its Protected Interoperable File Format (PIFF) based on the ISO Base Media File Format and most commonly used for Smooth Streaming, a form of adaptive bit rate streaming over HTTP.
As announced, this format can for example contain VC-1, WMA, H.264 and AAC compression formats.

Internet radio

internet radio stationinternetonline
In addition, BBC World Service has employed WMA Voice for its Internet radio streaming service.
Streaming audio formats include MP3, Ogg Vorbis, Windows Media Audio, RealAudio, and HE-AAC (or aacPlus).

Zune

Zune MarketplaceMicrosoft ZuneZune Video Marketplace
Some notable exceptions to this are the Microsoft Zune (limited to stereo), Xbox 360, Windows Mobile-powered devices with Windows Media Player 10 Mobile, newer Toshiba Gigabeat and Motorola devices, and devices running recent versions of the Rockbox alternative firmware.
WMA Pro (2-channel)