Windows Media Audio

Windows Media Audio is an audio data compression technology developed by Microsoft

Microsoft

Microsoft Corporation is an American public multinational corporation headquartered in Redmond, Washington, USA that develops, manufactures, licenses, and supports a wide range of products and services predominantly related to computing through its various product divisions...

. The name can be used to refer to its audio file format

Audio file format

An audio file format is a file format for storing digital audio data on a computer system. This data can be stored uncompressed, or compressed to reduce the file size. It can be a raw bitstream, but it is usually a container format or an audio data format with defined storage layer.-Types of...

or its audio codecs. It is a proprietary

Proprietary software

Proprietary software is computer software licensed under exclusive legal right of the copyright holder. The licensee is given the right to use the software under certain conditions, while restricted from other uses, such as modification, further distribution, or reverse engineering.Complementary...

technology that forms part of the Windows Media

Windows Media

Windows Media is a multimedia framework for media creation and distribution for Microsoft Windows. It consists of a software development kit with several application programming interfaces and a number of prebuilt technologies, and is the replacement of NetShow technologies.The Windows Media SDK...

framework. WMA consists of four distinct codecs. The original WMA codec, known simply as WMA, was conceived as a competitor to the popular MP3

MP3

MPEG-1 or MPEG-2 Audio Layer III, more commonly referred to as MP3, is a patented digital audio encoding format using a form of lossy data compression...

and RealAudio

RealAudio

RealAudio is a proprietary audio format developed by RealNetworks and first released in April 1995. It uses a variety of audio codecs, ranging from low-bitrate formats that can be used over dialup modems, to high-fidelity formats for music. It can also be used as a streaming audio format, that is...

codecs. WMA Pro, a newer and more advanced codec, supports multichannel

Surround sound

Surround sound encompasses a range of techniques such as for enriching the sound reproduction quality of an audio source with audio channels reproduced via additional, discrete speakers. Surround sound is characterized by a listener location or sweet spot where the audio effects work best, and...

and high resolution

Audio bit depth

In digital audio, bit depth describes the number of bits of information recorded for each sample. Bit depth directly corresponds to the resolution of each sample in a set of digital audio data...

audio. A lossless

Lossless data compression

Lossless data compression is a class of data compression algorithms that allows the exact original data to be reconstructed from the compressed data. The term lossless is in contrast to lossy data compression, which only allows an approximation of the original data to be reconstructed, in exchange...

codec, WMA Lossless, compresses audio data without loss of audio fidelity (the regular WMA format is lossy). And WMA Voice, targeted at voice content, applies compression using a range of low bit rate

Bit rate

In telecommunications and computing, bit rate is the number of bits that are conveyed or processed per unit of time....

Development history

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. Malvar was a senior researcher and manager of the Signal Processing Group at Microsoft Research

Microsoft Research

Microsoft Research is the research division of Microsoft created in 1991 for developing various computer science ideas and integrating them into Microsoft products. It currently employs Turing Award winners C.A.R. Hoare, Butler Lampson, and Charles P...

, whose team worked on the MSAudio project. The first finalized codec was initially referred to as MSAudio 4.0. It was later officially released as Windows Media Audio, as part of Windows Media Technologies 4.0. Microsoft claimed that WMA could produce files that were half the size of equivalent-quality MP3 files; Microsoft also claimed that WMA delivered "near CD-quality" audio at 64 kbit/s. The former claim however was rejected by some audiophile

Audiophile

An audiophile is a person who enjoys listening to recorded music, usually in a home. Some audiophiles are more interested in collecting and listening to music, while others are more interested in collecting and listening to audio components, whose "sound quality" they consider as important as the...

s. RealNetworks

RealNetworks

RealNetworks, Inc. is a provider of Internet media delivery software and services based in Downtown Seattle, Washington, United States. The company is the creator of RealAudio, a compressed audio format; RealVideo, a compressed video format; RealPlayer, a media player; RealDownloader, a download...

also challenged Microsoft's claims regarding WMA's superior audio quality compared to RealAudio.

Newer versions of WMA became available: Windows Media Audio 2 in 1999, Windows Media Audio 7 in 2000, Windows Media Audio 8 in 2001, and Windows Media Audio 9 in 2003. Microsoft first announced its plans to license WMA technology to third-parties in 1999. Although earlier versions of Windows Media Player

Windows Media Player

Windows Media Player is a media player and media library application developed by Microsoft that is used for playing audio, video and viewing images on personal computers running the Microsoft Windows operating system, as well as on Pocket PC and Windows Mobile-based devices...

played WMA files, support for WMA file creation was not added until the seventh version. In 2003, Microsoft released new audio codecs that were not compatible with the original WMA codec. These codecs were Windows Media Audio 9 Professional, Windows Media Audio 9 Lossless, and Windows Media Audio 9 Voice. Ibrahim Irfan Ahmed

Codecs

Each WMA file features a single audio track in one of following codecs: WMA, WMA Pro, WMA Lossless, or WMA Voice. These codecs are technically distinct and mutually incompatible. Each codec is further explained below.

Windows Media Audio (WMA) is the most common codec of the four WMA codecs. Colloquial usage of the term WMA, especially in marketing materials and device specifications, usually refers to this codec only. The first version of the codec released in 1999 is regarded as WMA 1. In the same year, the bit stream syntax, or compression algorithm, was altered in minor ways and became WMA 2. Since then, newer versions of the codec were released, but the decoding process remained the same, ensuring compatibility between codec versions. WMA is a lossy audio codec based on the study of psychoacoustics

Psychoacoustics

Psychoacoustics is the scientific study of sound perception. More specifically, it is the branch of science studying the psychological and physiological responses associated with sound...

. Audio signals that are deemed to be imperceptible to the human ear are encoded with reduced resolution during the compression process.

WMA can encode audio signals sampled at up to 48 kHz with up to two discrete channels (stereo

STEREO

STEREO is a solar observation mission. Two nearly identical spacecraft were launched into orbits that cause them to respectively pull farther ahead of and fall gradually behind the Earth...

). 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. WMA 9.1 also added support for low-delay audio, which reduces latency

Latency (engineering)

Latency is a measure of time delay experienced in a system, the precise definition of which depends on the system and the time being measured. Latencies may have different meaning in different contexts.-Packet-switched networks:...

for encoding and decoding.

Fundamentally, WMA is a transform coder based on modified discrete cosine transform

Modified discrete cosine transform

The modified discrete cosine transform is a Fourier-related transform based on the type-IV discrete cosine transform , with the additional property of being lapped: it is designed to be performed on consecutive blocks of a larger dataset,...

(MDCT), somewhat similar to AAC

Advanced Audio Coding

Advanced Audio Coding is a standardized, lossy compression and encoding scheme for digital audio. Designed to be the successor of the MP3 format, AAC generally achieves better sound quality than MP3 at similar bit rates....

, Cook

Cook Codec

The cook codec is a lossy audio compression codec developed by RealNetworks. It is also known as Cooker, Gecko, RealAudio G2, and RealAudio 8 low bitrate ....

and Vorbis

Vorbis

Vorbis is a free software / open source project headed by the Xiph.Org Foundation . The project produces an audio format specification and software implementation for lossy audio compression...

. The bit stream of WMA is composed of superframes, each containing 1 or more frames of 2048 samples. If the bit reservoir is not used, a frame is equal to a superframe. Each frame contains a number of blocks, which are 128, 256, 512, 1024, or 2048 samples long after being transformed into the frequency domain via the MDCT. In the frequency domain, masking for the transformed samples is determined, and then used to requantize the samples. Finally, the floating point

Floating point

In computing, floating point describes a method of representing real numbers in a way that can support a wide range of values. Numbers are, in general, represented approximately to a fixed number of significant digits and scaled using an exponent. The base for the scaling is normally 2, 10 or 16...

samples are decomposed into coefficient and exponent parts and independently huffman coded

Huffman coding

In computer science and information theory, Huffman coding is an entropy encoding algorithm used for lossless data compression. The term refers to the use of a variable-length code table for encoding a source symbol where the variable-length code table has been derived in a particular way based on...

. Stereo information is typically mid/side coded. At low bit rates, line spectral pairs

Line spectral pairs

Line spectral pairs or line spectral frequencies are used to represent linear prediction coefficients for transmission over a channel. LSPs have several properties that make them superior to direct quantization of LPCs...

(typically less than 17 kbit/s) and a form of noise coding (typically less than 33 kbit/s) can also be used to improve quality.

Like AAC and Ogg Vorbis, WMA was intended to address perceived deficiencies in the MP3 standard. Given their common design goals, it's not surprising that the three formats ended up making similar design choices. All three are pure transform codecs. Furthermore the MDCT implementation used in WMA is essentially a superset of those used in Ogg and AAC such that WMA iMDCT and windowing routines can be used to decode AAC and Ogg Vorbis almost unmodified. However, quantization and stereo coding is handled differently in each codec. The primary distinguishing trait of the WMA Standard format is its unique use of 5 different block sizes, compared to MP3, AAC, and Ogg Vorbis which each restrict files to just two sizes. WMA Pro extends this by adding a 6th block size used at 88.1/96 kHz sampling rate.

Certified PlaysForSure devices, as well as a large number of uncertified devices, ranging from portable hand-held music players to set-top DVD player

DVD player

A DVD player is a device that plays discs produced under both the DVD-Video and DVD-Audio technical standards, two different and incompatible standards. These devices were invented in 1997 and continue to thrive...

s, support the playback of WMA files. Most PlaysForSure-certified online stores distribute content using this codec only. In 2005, Nokia

Nokia

Nokia Corporation is a Finnish multinational communications corporation that is headquartered in Keilaniemi, Espoo, a city neighbouring Finland's capital Helsinki...

announced its plans to support WMA playback in future Nokia handsets. In the same year, an update was made available for the PlayStation Portable

PlayStation Portable

The is a handheld game console manufactured and marketed by Sony Corporation Development of the console was announced during E3 2003, and it was unveiled on , 2004, at a Sony press conference before E3 2004...

(version 2.60) which allowed WMA files to be played on the device for the first time.

Windows Media Audio Professional

Windows Media Audio Professional (WMA Pro) is an improved lossy codec closely related to WMA standard. It retains most of the same general coding features, but also features improved entropy coding and quantization strategies as well as more efficient stereo coding. Notably, many of the WMA standard's low bitrate features have been removed, as the core codec is designed for efficient coding at most bitrates. Its main competitors include AAC, HE-AAC

HE-AAC

High-Efficiency Advanced Audio Coding is a lossy data compression scheme for digital audio defined as a MPEG-4 Audio profile in ISO/IEC 14496-3. It is an extension of Low Complexity AAC optimized for low-bitrate applications such as streaming audio...

, Vorbis

Vorbis

Vorbis is a free software / open source project headed by the Xiph.Org Foundation . The project produces an audio format specification and software implementation for lossy audio compression...

, Dolby Digital, and DTS. It can support audio resolutions of up to 96 kHz and up to eight discrete channels (7.1 channel surround). WMA Pro also supports dynamic range compression, which reduces the volume difference between the loudest and quietest sounds in the audio track. According to Microsoft's Amir Majidimehr, WMA Pro can technically go beyond 7.1 surround sound and support "an unlimited number of channels."

The codec's bit stream syntax was frozen at the first version, WMA 9 Pro. Later versions of WMA Pro introduced low-bit rate encoding, low-delay audio, frequency interpolation mode, and an expanded range of sampling rate

Sampling rate

The sampling rate, sample rate, or sampling frequency defines the number of samples per unit of time taken from a continuous signal to make a discrete signal. For time-domain signals, the unit for sampling rate is hertz , sometimes noted as Sa/s...

and bit-depth encoding options. A WMA 10 Pro file compressed with frequency interpolation mode comprises a WMA 9 Pro track encoded at half the original sampling rate, which is then restored using a new compression algorithm. In this situation, WMA 9 Pro players which have not been updated to the WMA 10 Pro codec can only decode the lower quality WMA 9 Pro stream. Starting with WMA 10 Pro, eight channel encoding starts at 128 kbit/s, and tracks can be encoded at the native audio CD resolution (44.1 kHz, 16-bit), previously the domain of WMA Standard.

Despite a growing number of supported devices and its superiority over WMA, WMA Pro still has little hardware and software support. Some notable exceptions to this are the Microsoft Zune (limited to stereo), Xbox 360

Xbox 360

The Xbox 360 is the second video game console produced by Microsoft and the successor to the Xbox. The Xbox 360 competes with Sony's PlayStation 3 and Nintendo's Wii as part of the seventh generation of video game consoles...

, Windows Mobile

Windows Mobile

Windows Mobile is a mobile operating system developed by Microsoft that was used in smartphones and Pocket PCs, but by 2011 was rarely supplied on new phones. The last version is "Windows Mobile 6.5.5"; it is superseded by Windows Phone, which does not run Windows Mobile software.Windows Mobile is...

-powered devices with Windows Media Player 10 Mobile, newer Toshiba Gigabeat

Gigabeat

The Gigabeat is a line of digital audio players by Toshiba.-Gigabeat:The Gigabeat was first called the MobilPhile and later renamed to Gigabeat. It contained a monochrome LCD with blue backlighting, and a 5 GB removable PCMCIA hard drive. Its case was made of aluminum, and battery life is...

and Motorola

Motorola

Motorola, Inc. was an American multinational telecommunications company based in Schaumburg, Illinois, which was eventually divided into two independent public companies, Motorola Mobility and Motorola Solutions on January 4, 2011, after losing $4.3 billion from 2007 to 2009...

devices, and devices running recent versions of the Rockbox

Rockbox

Rockbox is a replacement for the standard firmware in various forms of digital audio players . It offers an alternative to the player's operating system, in many cases without removing the original firmware, which provides a plug-in architecture for adding various enhancements and functions...

alternative firmware. In addition, WMA Pro is a requirement for the WMV HD certification program. On the software side, Verizon utilizes WMA 10 Pro for its V CAST Music Service, and Windows Media Player 11

Windows Media Player

has promoted the codec as an alternative to WMA for copying audio CD tracks. WMA Pro is supported in Silverlight as of version 2 (though only in stereo mode). In the absence of the appropriate audio hardware, WMA Pro can automatically downmix

Downmixing

Downmixing is a general term used for manipulating audio where a number of distinct audio channels are mixed together to produce a lower number of channels...

multichannel audio to stereo or mono, and 24-bit resolution to 16-bit during playback.

A notable example of WMA Pro being used instead of WMA Standard is the NBC Olympics website which uses WMA 10 Pro in its low-bitrate mode at 48 kbit/s.

Windows Media Audio Lossless

Windows Media Audio Lossless (WMA Lossless) is a lossless audio codec that competes with ATRAC

ATRAC

Adaptive Transform Acoustic Coding is a family of proprietary audio compression algorithms developed by Sony. MiniDisc was the first commercial product to incorporate ATRAC in 1992. ATRAC allowed a relatively small disc like MiniDisc to have the same running time as CD while storing audio...

Advanced Lossless, Dolby TrueHD

Dolby TrueHD

Dolby TrueHD is an advanced lossless multi-channel audio codec developed by Dolby Laboratories which is intended primarily for high-definition home-entertainment equipment such as Blu-ray Disc and HD DVD. It is the successor to the AC-3 Dolby Digital surround sound codec which was used as the...

, DTS-HD Master Audio

DTS-HD Master Audio

DTS-HD Master Audio is a lossless audio codec created by Digital Theater System. It was previously known as DTS++. It is an extension of DTS which, when played back on devices which do not support the Master Audio or High Resolution extension, degrades to a "core" track which is lossy. DTS-HD...

, Apple Lossless

Apple Lossless

Apple Lossless Apple Lossless Apple Lossless (also known as ALAC (Apple Lossless Audio Codec), or ALE (Apple Lossless Encoder) is an audio codec developed by Apple Inc. for lossless data compression of digital music. After initially being proprietary for many years, in late 2011 Apple open sourced...

, Shorten

Shorten

Shorten is a file format used for compressing audio data. It is a form of data compression of files and is used to losslessly compress CD-quality audio files . Shorten is no longer developed and more recent lossless audio codecs such as FLAC, Monkey's Audio , TTA, and WavPack have become more...

, Monkey's Audio

Monkey's Audio

Monkey's Audio is a file format for audio data compression. Being a lossless format, Monkey's Audio does not discard data during the process of encoding, unlike lossy compression methods such as AAC, MP3, Vorbis and Musepack....

, FLAC

FLAC

FLAC is a codec which allows digital audio to be losslessly compressed such that file size is reduced without any information being lost...

, and WavPack

WavPack

WavPack is a free, open source lossless audio compression format developed by David Bryant.-Features:WavPack compression can compress 8-, 16-, 24-, and 32-bit fixed-point, and 32-bit floating point audio files in the .WAV file format. It also supports surround sound streams and high frequency...

(the last two have the advantage of being open source software and available for nearly any operating system

Operating system

An operating system is a set of programs that manage computer hardware resources and provide common services for application software. The operating system is the most important type of system software in a computer system...

). Designed for archival purposes, it compresses audio signals without loss of quality from the original using VBR. When decompressed, the audio signal is an exact replica of the original. The first version of the codec, WMA 9 Lossless, and its revisions support up to 96 kHz, 24-bit audio for up to 6 discrete channels (5.1 channel surround) with dynamic range compression control. The typical compression ratio for music varies between 1.7:1 and 3:1.

Hardware support for the codec is available on the Cowon A3 http://www.cowonglobal.com/product_wide/product_A3_feature.php, Cowon S9, Bang & Olufsen Serenata, Sony Walkman NWZ-A and NWZ-S series, Zune 4, 8

Zune 4, 8

The Zune 4, Zune 8, and Zune 16 are second-generation models of the Zune lineup, they were first announced on October 2, 2007 and released on November 13, 2007 in the United States and June 13, 2008 in Canada...

, 80

Zune 80

The Zune 80 and Zune 120 are portable media players developed by Microsoft in its Zune series of media players. The Zune 80 was announced on October 2, 2007 and was released on November 13, 2007. It, along with the Zune 4, 8, and 16, is part of the second generation of Zune devices. It features...

Zune 30

This article refers only to the Zune 30 model. For the main Zune article, click here.The Zune 30 was the first portable media player developed by Microsoft. It was released on November 14, 2006. It was simply named the Zune...

, Zune 120 (with firmware version 2.2 or later) and the new Zune HD

Zune HD

The Zune HD is a portable media player in the Zune product family released on September 15, 2009 by Microsoft. It is a direct competitor with the Apple iPod and iPhone series of mobile devices. It was initially released in 16 and 32 GB capacities. A 64 GB version was released on April 9, 2010...

, Xbox 360

Xbox 360

, Windows Mobile

Windows Mobile

-powered devices with Windows Media Player 10 Mobile, Toshiba Gigabeat S and V models, Toshiba T-400, the Meizu M3, and Best Buy

Best Buy

Best Buy Co., Inc. is an American specialty retailer of consumer electronics in the United States, accounting for 19% of the market. It also operates in Mexico, Canada & China. The company's subsidiaries include Geek Squad, CinemaNow, Magnolia Audio Video, Pacific Sales, and, in Canada operates...

's Insignia NS-DV, Pilot, and Sport music players. Contrary to some claims, the Archos

Archos

Archos is a French consumer electronics company that was established in 1988 by Henri Crohas. Archos manufactures portable media players and portable data storage devices. The name is an anagram of Crohas' last name, and it is also Greek for 'master'...

make of media devices do not support WMA Lossless, nor does the SONOS system. Like WMA Standard, WMA Lossless is being used by a few online stores to distribute music online. Similar to WMA Pro, the WMA Lossless decoder can perform downmixing when capable audio hardware is not present.

Windows Media Audio Voice

Windows Media Audio Voice (WMA Voice) is a lossy audio codec that competes with Speex

Speex

Speex is a patent-free audio compression format designed for speech and also a free software speech codec that may be used on VoIP applications and podcasts. It is based on the CELP speech coding algorithm. Speex claims to be free of any patent restrictions and is licensed under the revised BSD...

(used in Microsoft's own Xbox Live

Xbox Live

Xbox Live is an online multiplayer gaming and digital media delivery service created and operated by Microsoft Corporation. It is currently the only online gaming service on consoles that charges users a fee to play multiplayer gaming. It was first made available to the Xbox system in 2002...

online service), ACELP

ACELP

Algebraic code-excited linear prediction is a patented speech coding algorithm by VoiceAge Corporation in which a limited set of pulses is distributed as excitation to linear prediction filter....

, and other codecs. Designed for low-bandwidth, voice playback applications, it employs low-pass and high-pass filtering of sound outside the human speech frequency range to achieve higher compression efficiency than WMA. It can automatically detect sections of an audio track containing both voice and music and use the standard WMA compression algorithm instead. WMA Voice supports up to 22.05 kHz for a single channel (mono) only. Encoding is limited to constant bit rate (CBR) and up to 20 kbit/s. The first and only version of the codec is WMA 9 Voice.

Windows Mobile-powered devices with Windows Media Player 10 Mobile have native support for WMA 9 Voice playback. In addition, BBC World Service

BBC World Service

The BBC World Service is the world's largest international broadcaster, broadcasting in 27 languages to many parts of the world via analogue and digital shortwave, internet streaming and podcasting, satellite, FM and MW relays...

has employed WMA Voice for its Internet radio

Internet radio

Internet radio is an audio service transmitted via the Internet...

streaming service.

Sound quality

See codec listening test for a table of double-blind listening test results.

Microsoft claims that audio encoded with WMA sounds better than MP3 at the same bit rate; Microsoft also claims that audio encoded with WMA at lower bit rates sound better than MP3 at higher bit rates. Double blind listening tests with other lossy audio codecs have shown varying results, from failure to support Microsoft's claims about its superior quality to supremacy over other codecs. One independent test conducted in May 2004 at 128 kbit/s showed that WMA was roughly equivalent to LAME

LAME

LAME is a free software codec used to encode/compress audio into the lossy MP3 file format.-History:The name LAME is a recursive acronym for "LAME Ain't an MP3 Encoder". Around mid-1998, Mike Cheng created LAME 1.0 as a set of modifications against the "8Hz-MP3" encoder source code...

MP3; inferior to AAC and Vorbis; and superior to ATRAC3 (software version).

Some conclusions made by recent studies:

At 32 kbit/s, WMA Standard was noticeably better than LAME MP3, but not better than other modern codecs in a collective, independent test in July 2004.
At 48 kbit/s, WMA 10 Pro was ranked second after Nero
Nero AG
Nero is a global computer software company headquartered in Karlsbad, Germany. It is perhaps most well-known for its burning software, Nero Burning ROM.-History:The company was founded as Ahead Software GmbH in 1995 by Richard Lesser....

HE-AAC and better than WMA 9.2 in an independent listening test organized and supported by Sebastian Mares and Hydrogenaudio Forums in December 2006. This test, however, used CBR for WMA 10 Pro and VBR for the other codecs.
At 64 kbit/s, WMA Pro outperformed Nero HE-AAC in a commissioned, independent listening test performed by the National Software Testing Labs in 2005. Out of 300 participants, "71% of all listeners indicated that WMA Pro was equal to or better than HE AAC."
At 80 kbit/s and 96 kbit/s, WMA had lower quality than HE-AAC, AAC-LC, and Vorbis; near-equivalent quality to MP3, and better quality than MPC
Musepack
Musepack or MPC is an open source lossy audio codec, specifically optimized for transparent compression of stereo audio at bitrates of 160–180 kbit/s...

in individual tests done in 2005.
At 128 kbit/s, there was a four-way tie between aoTuV Vorbis, LAME MP3, WMA 9 Pro and AAC in a large scale test in January 2006, with each codec sounding close to the uncompressed music file for most listeners.
At 768 kbit/s, WMA 9 Pro delivered full-spectrum response at half the bit rate required for DTS in a comparative test done by EDN in October 2003. The test sample was a 48 kHz, 5.1 channel surround audio track.

Criticism of claimed quality

Microsoft's claims of WMA sound quality have frequently drawn complaints. "Some audiophiles challenge Microsoft's claims regarding WMA's quality," according to a published article from EDN. Another article from MP3 Developments wrote that Microsoft's claim about CD-quality audio at 64 kbit/s with WMA was "very far from the truth." At the early stages of WMA's development, a representative from RealNetworks claimed that WMA was a "clear and futile effort by Microsoft to catch up with RealAudio 8."

Microsoft has sometimes claimed that the sound quality of WMA at 64 kbit/s equals or exceeds that of MP3 at 128 kbit/s (both WMA and MP3 are considered near-transparent

Transparency (data compression)

In data compression or psychoacoustics, transparency is the ideal result of lossy data compression. If a lossy compressed result is perceptually indistinguishable from the uncompressed input, then the compression can be declared to be transparent...

at 192 kbit/s by most listeners). In a 1999 study funded by Microsoft, National Software Testing Laboratories

National Software Testing Laboratories

National Software Testing Laboratories, or NSTL, is an American company, established in 1983, which testscomputer hardware and software. The company provides certification , quality assurance, and benchmarking services. NSTL is the only authorized testing organization for the Qualcomm TRUE BREW...

(NSTL) found that listeners preferred WMA at 64 kbit/s to MP3 at 128 kbit/s (as encoded by MusicMatch Jukebox

Musicmatch Jukebox

Y!Music Musicmatch Jukebox, a remake of the original Musicmatch Jukebox made by Musicmatch, Inc., is an audio player that manages a digital audio library...

). However, a September 2003 public listening test conducted by Roberto Amorim found that listeners preferred 128 kbit/s MP3 to 64 kbit/s WMA audio with greater than 99% confidence

Confidence interval

In statistics, a confidence interval is a particular kind of interval estimate of a population parameter and is used to indicate the reliability of an estimate. It is an observed interval , in principle different from sample to sample, that frequently includes the parameter of interest, if the...

. This conclusion applied equally to other codecs at the same bitrate, leading him to conclude that:

It is important to note that both MP3 and WMA encoders have undergone active development and improvement for many years, so their relative quality may change over time.

A July 2007 public listening test by Sebastian Mares found that 64 kbit/s HE-AAC

HE-AAC

audio (encoded by Nero Digital

Nero Digital

Nero Digital is a brand name applied to a suite of MPEG-4-compatible video and audio compression codecs developed by Nero AG of Germany and Ateme of France...

) was statistically tie

Tie (draw)

To tie or draw is to finish a competition with identical or inconclusive results. The word "tie" is usually used in North America for sports such as American football. "Draw" is usually used in the United Kingdom, Ireland and the Commonwealth of Nations and it is usually used for sports such as...

d with 64 kbit/s WMA Pro audio, in terms of listener preference.

Players

Apart from Windows Media Player, most of the WMA compression formats can be played using ALLPlayer

ALLPlayer

ALLPlayer is a Polish freeware media player developed by ALLPlayer.org It was designed to allow watching videos with subtitles in a variety of formats. ALLPlayer is originated and developed by ALLCinema Ltd. Partnership. Unlike other media players, it does not use Windows Media Player to play...

, VLC media player

VLC media player

VLC media player is a free and open source media player and multimedia framework written by the VideoLAN project.VLC is a portable multimedia player, encoder, and streamer supporting many audio and video codecs and file formats as well as DVDs, VCDs, and various streaming protocols. It is able to...

, Media Player Classic

Media Player Classic

Media Player Classic is a compact media player for 32-bit and 64-bit Microsoft Windows. The application mimics the look and feel of the old, lightweight Windows Media Player 6.4 but integrates most options and features found in modern media players...

, MPlayer

MPlayer

MPlayer is a free and open source media player. The program is available for all major operating systems, including Linux and other Unix-like systems, Microsoft Windows and Mac OS X. Versions for OS/2, Syllable, AmigaOS and MorphOS are also available. The Windows version works, with some minor...

, RealPlayer

RealPlayer

RealPlayer is a cross-platform media player by RealNetworks that plays a number of multimedia formats including MP3, MPEG-4, QuickTime, Windows Media, and multiple versions of proprietary RealAudio and RealVideo formats.-History:...

, Winamp

Winamp

Winamp is a media player for Windows-based PCs and Android devices, written by Nullsoft, now a subsidiary of AOL. It is proprietary freeware/shareware, multi-format, extensible with plug-ins and skins, and is noted for its graphical sound visualization, playlist, and media library features.Winamp...

, Zune Software

Zune Software

The Zune software functions as management software for Windows Phone 7, Zune devices, and Microsoft Kin, a full media player application with a library, an interface to the Zune Marketplace, and as a media streaming server. Zune Software is used to sync with all devices with Zune functionality....

(with certain limitations—DSP plugin support and DirectSound output is disabled using the default WMA plugin), and many other software media players. The Microsoft Zune media management software supports most WMA codecs, but uses a variation of Windows Media DRM

Windows Media DRM

Windows Media DRM is a Digital Rights Management service for the Windows Media platform. It is designed to provide delivery of audio and/or video content over an IP network to a PC or other playback device in such a way that the distributor can control how that content is used.WMDRM includes the...

which is used by PlaysForSure.

The FFmpeg

FFmpeg

FFmpeg is a free software project that produces libraries and programs for handling multimedia data. The most notable parts of FFmpeg are libavcodec, an audio/video codec library used by several other projects, libavformat, an audio/video container mux and demux library, and the ffmpeg command line...

project has reverse-engineered and re-implemented the WMA codecs (except WMA Lossless) to allow their use on POSIX

POSIX

POSIX , an acronym for "Portable Operating System Interface", is a family of standards specified by the IEEE for maintaining compatibility between operating systems...

-compliant operating systems such as Linux

Linux

Linux is a Unix-like computer operating system assembled under the model of free and open source software development and distribution. The defining component of any Linux system is the Linux kernel, an operating system kernel first released October 5, 1991 by Linus Torvalds...

. The rockbox

Rockbox

project further extended this codec to be suitable for embedded cores, allowing playback on portable MP3 players and cell phones running open source software. RealNetworks has announced plans to support playback of DRM-unprotected WMA files in RealPlayer for Linux. On the Macintosh

Macintosh

The Macintosh , or Mac, is a series of several lines of personal computers designed, developed, and marketed by Apple Inc. The first Macintosh was introduced by Apple's then-chairman Steve Jobs on January 24, 1984; it was the first commercially successful personal computer to feature a mouse and a...

platform, Microsoft released a PowerPC

PowerPC

PowerPC is a RISC architecture created by the 1991 Apple–IBM–Motorola alliance, known as AIM...

version of Windows Media Player for Mac OS X

Mac OS X

Mac OS X is a series of Unix-based operating systems and graphical user interfaces developed, marketed, and sold by Apple Inc. Since 2002, has been included with all new Macintosh computer systems...

in 2003, but further development of the software has ceased. Microsoft currently endorses the third-party Flip4Mac

Flip4Mac

Flip4Mac is a trademarked brand name for Telestream, Inc.'s proprietary digital media tools for the Macintosh. It is particularly known for being the only QuickTime component for Mac OS X that supports Windows Media Video, although there is non-QuickTime OS X software that supports WMV...

WMA, a QuickTime

QuickTime

QuickTime is an extensible proprietary multimedia framework developed by Apple Inc., capable of handling various formats of digital video, picture, sound, panoramic images, and interactivity. The classic version of QuickTime is available for Windows XP and later, as well as Mac OS X Leopard and...

component that allows Macintosh users to play WMA files in any player that uses the QuickTime framework. Flip4Mac, however, does not currently support the Windows Media Audio Voice codec.

Encoders

Software that can export audio in WMA format include Windows Media Player, Windows Movie Maker

Windows Movie Maker

Windows Movie Maker is a video creating/editing software application, included in Microsoft Windows Me, XP, and Vista. It contains features such as effects, transitions, titles/credits, audio track, timeline narration, and Auto Movie. New effects and transitions can be made and existing ones can be...

, Microsoft Expression Encoder

Microsoft Expression Encoder

Microsoft Expression Encoder is a Windows-based program for encoding digital video for web-based video. Expression Encoder can be used to create video compressed VC-1 as well as H.264 for distribution via Microsoft Silverlight. Expression Encoder features a WPF-based modern graphical user...

, Sony Sound Forge, GOM Player

Gom player

GOM Player is a 32-bit media player for Microsoft Windows, distributed by the Gretech Corporation of South Korea. It is alleged that Gretech distributes GOM Player in violation of copyright law....

, RealPlayer

RealPlayer

, Adobe Premiere Pro

Adobe Premiere Pro

Adobe Premiere Pro is a timeline-based video editing software application. It is part of the Adobe Creative Suite, a suite of graphic design, video editing, and web development applications developed by Adobe Systems, though it can also be purchased separately. When purchased separately, it comes...

, Adobe Audition

Adobe Audition

Adobe Audition is a digital audio workstation from Adobe Systems featuring both a multitrack, non-destructive mix/edit environment and a destructive-approach waveform editing view.-Origins:...

, and Adobe Soundbooth

Adobe Soundbooth

Adobe Soundbooth was a digital audio editor by Adobe Systems Incorporated for Mac OS X, Windows Vista and 7. Adobe has described it as being "in the spirit of SoundEdit 16 and Cool Edit 2000". Adobe also has a more powerful program called Adobe Audition, which replaced Soundbooth as of Adobe...

. Microsoft Office OneNote

Microsoft Office OneNote

Microsoft OneNote is a computer program for free-form information gathering and multi-user collaboration. It can gather users' notes , drawings, screen clippings, and audio commentaries and share them with other users of Microsoft OneNote over the Internet...

supports encoding in all WMA codecs, and Windows Media Encoder

Windows Media Encoder

Windows Media Encoder is a freely downloadable trial version media encoder developed by Microsoft which enables content developers to convert or capture both live and prerecorded audio, video, and computer screen images to Windows Media formats for live and on-demand delivery. It is the successor...

supports all available bit rate and resolution options as well. Open source

Open source

The term open source describes practices in production and development that promote access to the end product's source materials. Some consider open source a philosophy, others consider it a pragmatic methodology...

players like VLC media player

VLC media player

can also do some encoding.

Digital rights management

The WMA codecs are most often used with the ASF container format, which has an optional DRM facility. Windows Media DRM, which can be used in conjunction with WMA, supports time-limited music subscription services such as those offered by unlimited download services, including MTV's URGE

URGE

The URGE digital music store was an online music distribution service run by MTV Networks. URGE was integrated into Windows Media Player 11.URGE was opened on May 17, 2006. Downloaded files come with restrictions on their use, enforced by Windows Media DRM, Microsoft's digital rights management...

, Napster

Napster

Napster is an online music store and a Best Buy company. It was originally founded as a pioneering peer-to-peer file sharing Internet service that emphasized sharing audio files that were typically digitally encoded music as MP3 format files...

, Rhapsody

Rhapsody (online music service)

Rhapsody is an online music store subscription service, launched in December 2001, and available in the United States only. On April 6, 2010, Rhapsody officially declared its independence from RealNetworks. Downloaded files come with restrictions on their use, enforced by Helix, Rhapsody's version...

, Yahoo! Music Unlimited

Yahoo! Music Unlimited

Yahoo! Music Unlimited was an on-demand online music service launched on May 11, 2005 and provided by Yahoo! Music.The service was discontinued on September 30, 2008.-Service:...

, and Virgin Digital

Virgin Digital

Virgin Digital was an online music store operated in the United Kingdom and United States by the Virgin Group. It launched on 2 September 2005 in the UK, and was refreshed in November 2006 to run through an internet browser, rather than the former Virgin Digital Player...

. Windows Media DRM, a component of PlaysForSure and Windows Media Connect

Windows Media Connect

Windows Media Connect is a UPnP AV server from Microsoft for Windows XP and later Windows operating systems, to share and stream media on a Windows computer to WMC clients. The first two releases of WMC were made available as stand-alone software, and included a client as well...

, is supported on many modern portable audio devices and streaming media clients such as Roku

Roku

Roku , is an American, privately held, consumer electronics company that sells home digital media products. The Company is based in Saratoga, California.- Company profile and products :...

, SoundBridge

SoundBridge

SoundBridge is a remote hardware device from Roku designed to play internet radio or digital audio streamed to it across a home network, either WiFi or Ethernet. SoundBridge devices directly browse the Radio Roku Internet Radio Guide....

, Xbox 360

Xbox 360

, and Wii

Wii

The Wii is a home video game console released by Nintendo on November 19, 2006. As a seventh-generation console, the Wii primarily competes with Microsoft's Xbox 360 and Sony's PlayStation 3. Nintendo states that its console targets a broader demographic than that of the two others...

. Players that support the WMA format but not Windows Media DRM cannot play DRM-protected files.You can do many things with it.

External links

Windows Media homepage at Microsoft
Listening tests (performed between 2002-2004) featuring Windows Media Audio at several bit rates
WMA page in Hydrogenaudio Wiki
Audio quality comparison between RealAudio and Windows Media Audio
Description of the algorithm used for Windows Media encryption
Windows Media Audio decoder source code at FFMpeg's git
mp3PRO vs MP3 - includes graphs comparing high-frequency performance for WMA/MP3/WAV

The source of this article is wikipedia, the free encyclopedia. The text of this article is licensed under the GFDL.

Development history

Codecs

Windows Media Audio

Windows Media Audio Professional

Windows Media Audio Lossless

Windows Media Audio Voice

Sound quality

Criticism of claimed quality

Players

Encoders

Digital rights management

See also

External links