Windows Media Video (WMV) is a series ofvideo codecs and their correspondingvideo coding formats developed byMicrosoft. It is part of theWindows Media framework. WMV consists of three distinct codecs: the original video compression technology, known asWMV, originally designed for Internet streaming applications as a competitor toRealVideo, andWMV Screen andWMV Image compression technologies, which cater to specialized content. After standardization by theSociety of Motion Picture and Television Engineers (SMPTE),[1][2] WMV version 9 was adapted for physical-delivery formats such asHD DVD andBlu-ray Disc and became known asVC-1.[3][4] Microsoft also developed adigital container format calledAdvanced Systems Format to store video encoded by Windows Media Video.
In 2003, Microsoft drafted avideo compression specification based on its WMV 9 format and submitted it to SMPTE for standardization. The standard was officially approved in March 2006 as SMPTE 421M, better known asVC-1, thus making the WMV 9 format an open standard. VC-1 became one of the three video formats for theBlu-ray video disc, along withH.262/MPEG-2 Part 2 andH.264/MPEG-4 AVC.[3][4]
AWMV file uses theAdvanced Systems Format (ASF)container format to encapsulate the encoded multimedia content. While the ASF can encapsulate multimedia in other encodings than those the WMV file standard specifies, those ASF files should use the.asffile extension and not the.wmv file extension.[5][failed verification]
The ASF container can optionally supportdigital rights management using a combination ofelliptic curve cryptography key exchange,DES block cipher, a custom block cipher,RC4 stream cipher and theSHA-1 hashing function.
Although WMV is generally packed into the ASF container format, it can also be put into theMatroska[6] container format (with file extension.mkv), orAVI container format (extension.avi). One common way to store WMV in an AVI file is to use the WMV 9Video Compression Manager (VCM) codec implementation.[7][8]
Windows Media Video (WMV) is the most recognizedvideo compression format within the WMV family. Usage of the termWMV often refers to the Microsoft Windows Media Video format only. Its main competitors areMPEG-4 AVC,AVS,RealVideo, andMPEG-4 ASP. The first version of the format, WMV 7, was introduced in 1999, and was built upon Microsoft's implementation ofMPEG-4 Part 2.[9] Continued proprietary development led to newer versions of the format, but thebit stream syntax was not frozen until WMV 9.[10] While all versions of WMV supportvariable bit rate,average bit rate, andconstant bit rate, WMV 9 introduced several important features including native support forinterlaced video, non-squarepixels, andframe interpolation.[11] WMV 9 also introduced a new profile titledWindows Media Video 9 Professional,[12] which is activated automatically whenever the video resolution exceeds 300,000 pixels (e.g., 528 px × 576 px, 640 px × 480 px or 768 px × 432 px and beyond) and the bitrate 1 Mbit/s[citation needed]. It is targeted towards high-definition video content, at resolutions such as720p and1080p.
TheSimple andMain profile levels in WMV 9 are compliant with the same profile levels in theVC-1 specification.[13] TheAdvanced Profile in VC-1 is implemented in a new WMV format calledWindows Media Video 9 Advanced Profile. It improves compression efficiency for interlaced content and is made transport-independent, making it able to be encapsulated in anMPEG transport stream orRTP packet format. The format is not compatible with previous WMV 9 formats, however.[14]
WMV is a mandatory video format forPlaysForSure-certified online stores and devices, as well asPortable Media Center devices. TheMicrosoft Zune,Xbox 360,Windows Mobile-powered devices with Windows Media Player, as well as many uncertified devices, support the format.[15]WMV HD mandates the use of WMV 9 for its certification program, at quality levels specified by Microsoft.[16] WMV used to be the only supported video format for theMicrosoft Silverlight platform, but the H.264 format is now also supported starting with version 3.[17]
Windows Media Video Screen (WMV Screen) are video formats that specialise inscreencast content. They can capture live screen content, or convert video from third-party screen-capture programs into WMV 9 Screen files. They work best when the source material is mainly static and contains a small colorpalette.[18]
One of the uses for the format is computer step-by-step demonstration videos. The first version of the format was WMV 7 Screen. The second version, WMV 9 Screen, supports VBR encoding in addition to CBR.[18] Additionally there is MSA1 (aka “MS ATC Screen codec” or “MSS3”) which is used inLive Meeting 2007.FourCCs for the formats areMSS1,MSS2 andMSA1.[19]
Windows Media Video Image (WMV Image) is a videoslideshow format. The format works by applying timing,panning and transition effects to a series of images during playback.[20] The codec achieves a higher compression ratio and image quality than WMV 9 for still images as files encoded with WMV Image store static images rather than full-motion video.
Since the format relies on the decoder (player) to generate video frames in real-time, playing WMV Image files even at moderate resolutions (e.g. 30frames per second at 1024 px × 768 px resolution) requires heavy computer processing. The latest version of the format, WMV 9.1 Image, used byPhoto Story 3, features additional transformation effects, but is not compatible with the original WMV 9 Image format.[20]
Hardware support for WMV Image is available from Portable Media Centers,Windows Mobile-powered devices with Windows Media Player 10 Mobile.[15]
Since no known domestic DVD player supports this format, users of Photo Story 3 wishing to generate material capable of being played in a DVD player will first have to convert toMPEG-2 before burning a DVD (average file sizes in MPEG-2 are 5 to 6 times the .wmv file).
| Public Name | FourCC | Description |
|---|---|---|
| Microsoft MPEG-4 version 1 | MPG4 | Video for Windows-based codec. Non-standard MPEG-4 codec incompatible with the later standardized version ofMPEG-4 Part 2. |
| Microsoft MPEG-4 version 2 | MP42 | VfW-based codec. Non-compliant with finalized MPEG-4 part 2 standard. |
| Microsoft MPEG-4 version 3 | MP43 | VfW-based codec. Non-compliant with finalized MPEG-4 part 2 standard. Eventually locked for encoding only with ASF files (build 3688 and earlier could also encode to AVI).[21] |
| Microsoft ISO MPEG-4 version 1 | MP4S | DirectX Media Objects (DMO)-based codec. MPEG-4Simple Profile compliant. |
| Microsoft ISO MPEG-4 version 1.1 | M4S2 | MPEG-4Advanced Simple Profile compliant.[22] |
| Windows Media Video 7 | WMV1 | DMO-based codec. |
| Windows Media Screen 7 | MSS1 | DMO-based codec. Optimized for low-bitrate sequential screen captures or screencasts. Deprecated in favor of Windows Media 9 Screen codec. |
| Windows Media Video 8 | WMV2 | DMO-based codec. |
| Windows Media Video 9 | WMV3 | DMO-based codec. Video for Windows (VfW/VCM) version also available.[1] |
| Windows Media Video 9 Screen | MSS2 | DMO-based codec. Optimized for low-bitrate sequential screen captures or screencasts. |
| Windows Media Video 9.1 Image | WMVP | DMO-based codec. Optimized for encoding video from sequential bitmap images. Used, for instance, by Photo Story. |
| Windows Media Video 9.1 Image V2 | WVP2 | DMO-based codec. Optimized for encoding video from sequential bitmap images. Used, for instance, by Photo Story. |
| Windows Media Video 9 Advanced Profile | WMVA | DMO-based codec. Deprecated as non-VC-1-compliant. |
| Windows Media Video 9 Advanced Profile | WVC1 | DMO-based codec. VC-1 compliant format. |
The audio format used in conjunction with Windows Media Video is typically some version ofWindows Media Audio, or in rarer cases, the deprecated SiproACELP.net audio format. Microsoft recommends that ASF files containing non-Windows Media formats use the generic.ASF file extension.
Software that can play WMV files includesWindows Media Player,RealPlayer,MPlayer,Media Player Classic,VLC Media Player andK-Multimedia Player. The Microsoft Zune media management software supports the WMV format, but uses a Zune-specific variation ofWindows Media DRM which is used by PlaysForSure. Many third-party players exist for various platforms such asLinux that use theFFmpeg implementation of the WMV format.
On theMacintosh platform, Microsoft released aPowerPC version of Windows Media Player forMac OS X in 2003,[23] but further development of the software ceased. From January 2006 to May 2014, Microsoft endorsed and distributed the 3rd partyFlip4Mac, aQuickTime Component developed byTelestream that allowed Macintosh users to play WMV files in any player that used the QuickTime framework.[24][25] Telestream ended sales of Flip4Mac on 1 July 2019 and officially ended support on 28 June 2020.[26] The Elmedia player, which can play WMV files on Macintosh computers, is still available.
Many programs can export video in WMV format; a few examples areWindows Movie Maker,Windows Media Encoder,Microsoft Expression Encoder,Sorenson Squeeze,[27]Vegas Pro,[28]AVS Video Editor,VSDC Free Video Editor,Telestream Episode,Telestream FlipFactory,[29][30] andFFmpeg.
Programs that encode using the WMV Image format includeWindows Media Encoder,AVS Video Editor, andPhoto Story.
While none of the WMV formats themselves contain anydigital rights management facilities, the ASF container format, in which a WMV stream may be encapsulated, can. Windows Media DRM, which can be used in conjunction with WMV, supports time-limited subscription video services such as those offered byCinemaNow.[31] Windows Media DRM, a component of PlaysForSure andWindows Media Connect, is supported on many modern portable video devices and streaming media clients such as the Xbox 360.
WMV has been the subject of numerous complaints from users and the press. Users dislike the digital rights management system which is sometimes attached to WMV files.[32] In 2007, the loss of the ability to restore licenses for WMV files in the Windows Media Player 11 was not positively received.[32]
As a sidenote, his muxer filter will also allow transmuxing of Microsoft WMV9 video files ( ASF/WMV container ) fine into matroska files, from Graphedit, and with WMV9 VCM installed on your PC you can even open and edit the files in latest VirtualdubMod
