Windows Media Audio
RealNetworks also challenged Microsoft's claims regarding WMA's superior audio quality compared to RealAudio.
The sole exception to this is the WMA 10 Professional codec whose Low Bit Rate (LBR) mode is only backwards compatible with the older WMA Professional decoders at a half sampling rate (similar to how HE-AAC is backwards compatible with AAC-LC).
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 bitrate streaming over HTTP.
These formats are implemented differently from one another, such that they are technically distinct and mutually incompatible; that is to say, a device or software compatible with one sub-format does not therefore automatically support any of the other codecs.
The colloquial usage of the term WMA, especially in marketing materials and device specifications, usually refers to this codec only.
In the same year, the bit stream syntax, or compression algorithm, was altered in minor ways and became WMA 2.
Audio signals that are deemed to be imperceptible to the human ear are encoded with reduced resolution during the compression process.
Finally, the floating point samples are decomposed into coefficient and exponent parts and independently huffman coded.
[20] In the same year, an update was made available for the PlayStation Portable (version 2.60) which allowed WMA files to be played on the device for the first time.
[22] WMA Pro also supports dynamic range compression, which reduces the volume difference between the loudest and quietest sounds in the audio track.
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.
Designed for archival purposes,[40] it compresses audio signals without loss of quality from the original using VBR.
[40][41][42] Hardware support for the codec is available on the Cowon A3,[43] Cowon S9, Bang & Olufsen Serenata[44] Sony Walkman NWZ-A and NWZ-S series, Zune 4, 8, 80 30, Zune 120 (with firmware version 2.2 or later) and the Zune HD, Xbox 360,[29] Windows Mobile-powered devices with Windows Media Player 10 Mobile,[30] Windows Phone (version 8 and above), Toshiba Gigabeat S and V models, Toshiba T-400, the Meizu M3, and Best Buy's Insignia NS-DV, Pilot, and Sport music players.
Designed for low-bandwidth, voice playback applications,[48] 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.
One independent test conducted in May 2004 at 128 kbit/s showed that WMA was roughly equivalent to LAME MP3; inferior to AAC and Vorbis; and superior to ATRAC3 (software version).
[51] Some studies concluded: 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.
In a 1999 study funded by Microsoft, National Software Testing Laboratories (NSTL) found that listeners preferred WMA at 64 kbit/s to MP3 at 128 kbit/s (as encoded by MusicMatch Jukebox).
[54] Both MP3 and WMA encoders have undergone active development and improvement for many years, so their relative quality may change over time.
The FFmpeg project has reverse-engineered and re-implemented the WMA codecs to allow their use on POSIX-compliant operating systems such as Linux.
The 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-free WMA files in RealPlayer for Linux.
[57] On the Macintosh platform, Microsoft released a PowerPC version of Windows Media Player for Mac OS X in 2003,[58] but further development of the software has ceased.
There are many proprietary and open source software packages that can export audio in WMA format, including amongst many others Windows Media Player, Windows Movie Maker, Microsoft Expression Encoder, Sony Sound Forge, GOM Player, RealPlayer,[62] Adobe Premiere Pro,[63] Adobe Audition,[64] Adobe Soundbooth, and VLC media player.
Players that support the WMA format but not Windows Media DRM cannot play DRM-protected files.
