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59-691: 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 , 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

118-438: A .wav or .aiff file) has long been a standard across multiple platforms, but its transmission over networks is slow and expensive compared with more modern compressed formats, such as Opus and MP3. Many multimedia data streams contain both audio and video , and often some metadata that permits synchronization of audio and video. Each of these three streams may be handled by different programs, processes, or hardware; but for

177-660: 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 ). Both MP3 and WMA encoders have undergone active development and improvement for many years, so their relative quality may change over time. Apart from Windows Media Player, most of the WMA compression formats can be played using ALLPlayer , VLC media player , Media Player Classic , MPlayer , RealPlayer , Winamp , Zune Software (with certain limitations—DSP plugin support and DirectSound output

236-432: 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

295-407: A bidirectional bytestream. The Internet media type for an arbitrary bytestream is application/octet-stream . Other media types are defined for bytestreams in well-known formats. Often the contents of a bytestream are dynamically created, such as the data from the keyboard and other peripherals (/dev/tty), data from the pseudorandom number generator ( /dev/urandom ), etc. In those cases, when

354-484: A byte-parallel loading method as well, this usage may have originated based on the common method of configuring the FPGA from a serial bit stream, typically from a serial PROM or flash memory chip. The detailed format of the bitstream for a particular FPGA is typically proprietary to the FPGA vendor. In mathematics, several specific infinite sequences of bits have been studied for their mathematical properties; these include

413-518: A combination of elliptic curve cryptography key exchange, DES block cipher, a custom block cipher, RC4 stream cipher and the SHA-1 hashing function. See Windows Media DRM for further information. 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,

472-435: A communication channel may use a signalling method that does not directly translate to bits (for instance, by transmitting signals of multiple frequencies) and typically also encodes other information such as framing and error correction together with its data. The term bitstream is frequently used to describe the configuration data to be loaded into a field-programmable gate array (FPGA). Although most FPGAs also support

531-501: A form of adaptive bitrate streaming over HTTP. Related industry standards such as DECE UltraViolet and MPEG-DASH have not standardized WMA as a supported audio codec, deciding in favor of the more industry-prevalent MPEG and Dolby audio codecs. Each WMA file features a single audio track in one of the four sub-formats: WMA, WMA Pro, WMA Lossless, or WMA Voice. These formats are implemented differently from one another, such that they are technically distinct and mutually incompatible; that

590-709: 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, 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

649-531: A lower bit rate. There are thousands of audio and video codecs, ranging in cost from free to hundreds of dollars or more. This variety of codecs can create compatibility and obsolescence issues. The impact is lessened for older formats, for which free or nearly-free codecs have existed for a long time. The older formats are often ill-suited to modern applications, however, such as playback on small portable devices. For example, raw uncompressed PCM audio (44.1 kHz, 16-bit stereo, as represented on an audio CD or in

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708-572: A range of 206 to 411 MB, at bit rates of 470 to 940 kbit/s. The result is a bit-for-bit duplicate of the original audio file; in other words, the audio quality on the CD will be the same as the file when played back. WMA Lossless uses the same .WMA file extension as other Windows Media Audio formats. It supports 6 discrete channels and up to 24-bit/96 kHz lossless audio. The format has never been publicly documented, although an open-source decoder has been reverse-engineered for non-Microsoft platforms by

767-457: Is a portmanteau of encoder/decoder . A coder or encoder encodes a data stream or a signal for transmission or storage, possibly in encrypted form, and the decoder function reverses the encoding for playback or editing. Codecs are used in videoconferencing , streaming media , and video editing applications. In the mid-20th century, a codec was a device that coded analog signals into digital form using pulse-code modulation (PCM). Later,

826-616: Is a sequence of bytes . Typically, each byte is an 8-bit quantity , and so the term octet stream is sometimes used interchangeably. An octet may be encoded as a sequence of 8 bits in multiple different ways (see bit numbering ) so there is no unique and direct translation between bytestreams and bitstreams. Bitstreams and bytestreams are used extensively in telecommunications and computing . For example, synchronous bitstreams are carried by SONET , and Transmission Control Protocol transports an asynchronous bytestream. In practice, bitstreams are not used directly to encode bytestreams;

885-407: Is a transform coder based on modified discrete cosine transform (MDCT), somewhat similar to AAC , Cook and Vorbis . 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 several blocks, which are 128, 256, 512, 1024, or 2048 samples long after being transformed into

944-656: Is an improved lossy codec closely related to WMA standards. 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 , Vorbis , Dolby Digital, and DTS. It supports 16-bit and 24-bit sample bit depth, sampling rates up to 96 kHz, and up to eight discrete channels ( 7.1 channel surround ). WMA Pro also supports dynamic range compression , which reduces

1003-635: Is available on the Cowon A3, Cowon S9, Bang & Olufsen Serenata 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 , Windows Mobile -powered devices with Windows Media Player 10 Mobile, 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. The Logitech Squeezebox Touch now supports

1062-409: Is being compressed and uses it as a disguise. This disguise appears as a codec download through a pop-up alert or ad. When a user goes to click or download that codec, the malware is then installed on the computer. Once a fake codec is installed it is often used to access private data, corrupt an entire computer system or to keep spreading the malware. One of the previous most used ways to spread malware

1121-711: 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 which is used by PlaysForSure. 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. On

1180-534: 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 88.2/96 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 players , support

1239-573: Is in most circumstances contained in the Advanced Systems Format (ASF), a proprietary Microsoft container format for digital audio or digital video . The ASF container format specifies how metadata about the file is to be encoded, similar to the ID3 tags used by MP3 files. Metadata may include song name, track number, artist name, and also audio normalization values. This container can optionally support digital rights management (DRM) using

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1298-401: Is no longer identifiable (visually, audibly, or both). Using more than one codec or encoding scheme successively can also degrade quality significantly. The decreasing cost of storage capacity and network bandwidth has a tendency to reduce the need for lossy codecs for some media. Many popular codecs are lossy. They reduce quality in order to maximize compression. Often, this type of compression

1357-441: Is not an ISO standard . There are also other well-known container formats, such as Ogg , ASF , QuickTime , RealMedia , Matroska , and DivX Media Format . MPEG transport stream , MPEG program stream , MP4 , and ISO base media file format are examples of container formats that are ISO standardized. Fake codecs are used when an online user takes a type of codec and installs viruses and other malware into whatever data

1416-676: Is third-party WMA software for Android devices. WMA format can be played on almost all Windows Mobile and later Windows Phone devices. 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 , Adobe Premiere Pro , Adobe Audition , Adobe Soundbooth , and VLC media player . Microsoft Office OneNote supports encoding in all WMA codecs, and Windows Media Encoder supports all available bit rate and resolution options as well. The WMA codecs are most often used with

1475-403: Is to say, a device or software compatible with one sub-format does not therefore automatically support any of the other codecs. Each codec is further explained below. Windows Media Audio (WMA) is the most common codec of the four WMA codecs. The colloquial usage of the term WMA , especially in marketing materials and device specifications, usually refers to this codec only. The first version of

1534-630: Is virtually indistinguishable from the original uncompressed sound or images, depending on the codec and the settings used. The most widely used lossy data compression technique in digital media is based on the discrete cosine transform (DCT), used in compression standards such as JPEG images, H.26x and MPEG video, and MP3 and AAC audio. Smaller data sets ease the strain on relatively expensive storage sub-systems such as non-volatile memory and hard disk , as well as write-once-read-many formats such as CD-ROM , DVD , and Blu-ray Disc . Lower data rates also reduce cost and improve performance when

1593-743: The Baum–Sweet sequence , Ehrenfeucht–Mycielski sequence , Fibonacci word , Kolakoski sequence , regular paperfolding sequence , Rudin–Shapiro sequence , and Thue–Morse sequence . On most operating systems , including Unix-like and Windows , standard I/O libraries convert lower-level paged or buffered file access to a bytestream paradigm. In particular, in Unix-like operating systems, each process has three standard streams , which are examples of unidirectional bytestreams. The Unix pipe mechanism provides bytestream communications between different processes. Compression algorithms often code in bitstreams, as

1652-667: The Macintosh platform, Microsoft released a PowerPC version of Windows Media Player for Mac OS X in 2003, but further development of the software has ceased. Microsoft currently endorses the third-party Flip4Mac WMA, a QuickTime 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. The core Android platform does not itself support WMA, but there

1711-553: The Rockbox 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 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

1770-485: The libav and ffmpeg projects. Windows Media Audio Lossless (WMA Lossless) is a lossless audio codec that competes with ATRAC Advanced Lossless, Dolby TrueHD , DTS-HD Master Audio , Shorten , Monkey's Audio , FLAC , Apple Lossless , and WavPack (Since late 2011, the last three have the advantage of being open source software and available for nearly any operating system .) Designed for archival purposes, it compresses audio signals without loss of quality from

1829-563: The 8 bits offered by a byte (the smallest addressable unit of memory) may be wasteful. Although typically implemented in low-level languages , some high-level languages such as Python and Java offer native interfaces for bitstream I/O. One well-known example of a communication protocol which provides a byte-stream service to its clients is the Transmission Control Protocol (TCP) of the Internet protocol suite , which provides

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1888-648: 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 , Napster , Rhapsody , Yahoo! Music Unlimited , and Virgin Digital . Windows Media DRM, a component of PlaysForSure and Windows Media Connect , is supported on many modern portable audio devices and streaming media clients such as Roku , SoundBridge , Xbox 360 , and Wii . Players that support

1947-405: The WMA format but not Windows Media DRM cannot play DRM-protected files. Codec A codec is a device or computer program that encodes or decodes a data stream or signal . Codec is a portmanteau of coder/decoder . In electronic communications, an endec is a device that acts as both an encoder and a decoder on a signal or data stream, and hence is a type of codec. Endec

2006-763: The Windows Media Source Filter ( DirectShow codec), later being removed in Windows Vista with the addition of Media Foundation. Although earlier versions of Windows Media Player 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 . All versions of WMA released since version 9.0 – namely 9.1, 9.2, and 10 – have been backwards compatible with

2065-538: The appropriate audio hardware, WMA Pro can automatically downmix 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 9 Lossless is a lossless incarnation of Windows Media Audio, an audio codec by Microsoft , released in early 2003. It compresses an audio CD to

2124-435: 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 have been 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 . Audio signals that are deemed to be imperceptible to

2183-675: The data is transmitted, e.g., over the internet. Two principal techniques are used in codecs, pulse-code modulation and delta modulation . Codecs are often designed to emphasize certain aspects of the media to be encoded. For example, a digital video (using a DV codec) of a sports event needs to encode motion well but not necessarily exact colors, while a video of an art exhibit needs to encode color and surface texture well. Audio codecs for cell phones need to have very low latency between source encoding and playback. In contrast, audio codecs for recording or broadcasting can use high-latency audio compression techniques to achieve higher fidelity at

2242-421: The destination of a bytestream (the consumer) uses bytes faster than they can be generated, the system uses process synchronization to make the destination wait until the next byte is available. When bytes are generated faster than the destination can use them and the producer is a software algorithm, the system pauses it with the same process synchronization techniques. When the producer supports flow control ,

2301-465: 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 , Windows Mobile -powered devices with Windows Media Player 10 Mobile, newer Toshiba Gigabeat and Motorola devices, and devices running recent versions of

2360-455: The format natively despite previously only supporting it via transcoding. 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. As of 2012, the ffmpeg and libav projects have open source WMA Lossless decoders based on reverse engineering of

2419-406: 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 samples are decomposed into coefficient and exponent parts and independently huffman coded . Stereo information is typically mid/side coded. At low bit rates, line spectral pairs (typically less than 17 kbit/s) and

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2478-528: 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 ). 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 for encoding and decoding. Fundamentally, WMA

2537-408: The multimedia data streams to be useful in stored or transmitted form, they must be encapsulated together in a container format . Lower bitrate codecs allow more users, but they also have more distortion. Beyond the initial increase in distortion, lower bit rate codecs also achieve their lower bit rates by using more complex algorithms that make certain assumptions, such as those about the media and

2596-448: The name was also applied to software for converting between digital signal formats, including companding functions. An audio codec converts analog audio signals into digital signals for transmission or encodes them for storage. A receiving device converts the digital signals back to analog form using an audio decoder for playback. An example of this is the codecs used in the sound cards of personal computers. A video codec accomplishes

2655-624: The official decoder. Only 16-bit WMA files can be successfully decoded by ffmpeg as of June 20, 2012. Windows Media Audio Voice (WMA Voice) is a lossy audio codec that competes with Speex (used in Microsoft's own Xbox Live online service), ACELP , 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

2714-421: The original stream. If preserving the original quality of the stream is more important than eliminating the correspondingly larger data sizes, lossless codecs are preferred. This is especially true if the data is to undergo further processing (for example, editing ) in which case the repeated application of processing (encoding and decoding) on lossy codecs will degrade the quality of the resulting data such that it

2773-400: 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

2832-436: The original v9 decoder and are therefore not considered separate codecs. 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). Full fidelity decoding of WMA 10 Professional LBR bitstreams requires a WMA version 10 or newer decoder. A WMA file

2891-538: The packet loss rate. Other codecs may not make those same assumptions. When a user with a low bitrate codec talks to a user with another codec, additional distortion is introduced by each transcoding . Audio Video Interleave (AVI) is sometimes erroneously described as a codec, but AVI is actually a container format, while a codec is a software or hardware tool that encodes or decodes audio or video into or from some audio or video format. Audio and video encoded with many codecs might be put into an AVI container, although AVI

2950-470: The playback of WMA files. Most PlaysForSure-certified online stores distribute content using this codec only. In 2005, Nokia announced its plans to support WMA playback in future Nokia handsets. 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. Windows Media Audio Professional (WMA Pro)

3009-445: 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

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3068-612: The same task for video signals. When implementing the Infrared Data Association (IrDA) protocol, an endec may be used between the UART and the optoelectronic systems. In addition to encoding a signal, a codec may also compress the data to reduce transmission bandwidth or storage space. Compression codecs are classified primarily into lossy codecs and lossless codecs. Lossless codecs are often used for archiving data in compressed form while retaining all information present in

3127-713: 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 audiophiles and both claims have been refuted through publicly-available codec listening tests . RealNetworks 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. Prior to Windows XP , WMA files were primarily streamed using

3186-540: 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 has employed WMA Voice for its Internet radio streaming service. Microsoft claims that audio encoded with WMA sounds better than MP3 at

3245-465: The system only sends the ready signal when the consumer is ready for the next byte. When the producer can not be paused—a keyboard or some hardware that does not support flow control—the system typically attempts to temporarily store the data until the consumer is ready for it, typically using a queue . Often the receiver can empty the buffer before it gets completely full. A producer that continues to produce data faster than it can be consumed, even after

3304-649: The volume difference between the loudest and quietest sounds in the audio track. According to Microsoft's Amir Majidimehr, WMA Pro could theoretically go beyond 7.1 surround sound and support "an unlimited number of channels"; however, Microsoft chose to limit its current capability to eight (7.1 discrete 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 and bit-depth encoding options. A WMA 10 Pro file compressed with frequency interpolation mode comprises

3363-424: 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 at 192 kbit/s by most listeners). In

3422-416: Was fake AV pages and with the rise of codec technology, both have been used in combination to take advantage of online users. This combination allows fake codecs to be automatically downloaded to a device through a website linked in a pop-up ad, virus/codec alerts or articles as well. Bit stream A bitstream (or bit stream ), also known as binary sequence , is a sequence of bits . A bytestream

3481-445: Was roughly equivalent to LAME MP3; inferior to AAC and Vorbis; and superior to ATRAC3 (software version). 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. Another article from MP3 Developments wrote that Microsoft's claim about CD-quality audio at 64 kbit/s with WMA

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