sallrea zacharyasz deahanna
Rubi Strycker
The Windows Media Audio and Video codecs are a collection of objects that you can use to compress and decompress digital media data. Each codec consists of two objects, an encoder and a decoder. This part of the documentation describes how to use the features of the Windows Media Audio and Video codecs to produce and consume compressed data streams.
This documentation is primarily for developers who want to use Windows Media codecs in their C++-based media applications. For a technical overview of the features of the Windows Media codecs, see About the Windows Media Codecs.
The term codec is an amalgamation of the terms compressor and decompressor. A codec is usually implemented as a pair of COM objects: one for encoding content, and another for decoding content. In some cases the COM objects occupy the same dynamically linked library (DLL).
Not only are there different codecs for audio and for video, but also different codecs for different kinds of content that you might want to put into an audio or video file. The algorithms used to compress and decompress data for spoken words differ from the algorithms used to compress and decompress music data.
The most recent versions of the codec objects also enable access to some legacy codecs, including Windows Media Video 7 and 8, Windows Media Screen 7, the older Microsoft MPEG-4 codecs, and the Microsoft ISO MPEG-4 codecs.
1. MPlayer for OSX Version 1.0 rc2 will play the MSS2 Windows Media Video 9 Screen codec. There is no plug-in for watching the video in Safari, however you can use RCDefaultApp to change the Safari mime-type for video/x-ms-wmv so that it uses MPlayer for OSX. This will pop open a new mplayer window and play the video.
2. The Windows Media Video 9 Screen codec has a corresponding codec in Apple Quicktime called the Animation codec. A Third Party Windows tool like Movavi Video Converter can read the Video 9 Screen codec file and save it to the Quicktime Animation codec format which will play on the Mac.
#1 works because that project uses dmo to load the windows codecs written to read the format, the newer binaries for MPlayer for OSX Extended didn't really work, only the older version was reliable. This has only been tested on OSX 10.6.8 on a 32 bit Intel machine, so there maybe a different behavior on a 64 bit machine
#2 works because if you start from a Windows machine the native codec is available, and both 9 Screen and Animation are optimized for screen casting, that is they are similar in purpose so there is little if any loss of quality. Conversion is uncommonly fast it zips right along. The Fonts are very legible. After converting to Animation, Quicktime Pro can convert it to H.264 and the view still looks very good. You might want to use QTP because it can also 'hint' the file properly and can save it to device specific formats like AppleTV for presentation. Do not forget to change the Movavi/QPT settings when converting to animation codec to 'Best' quality otherwise it will degrade the video.
There was a question about this topic and suggested that Microsoft Photo Story would publish files with yet another variant of the wmv file using a different codec that specializes in "image" presentarion.
I would imagine this is due to the Microsoft codec interpolating the motion as its decoded where as the Apple codec must render the motion in its animation codec. There are differences. But it is barely noticable.
MPlayer for OS X Version 1.0 rc2 link my Mac OS X 10.6.8 desktop running MPlayer displaying a Windows Media Video 9 Screen codec file, the quality is better than on Windows (in my opinion), I have read VLC does support the same dmo loading mechanism for windows codecs but it is un-tested and so far I have not been able to get VLC to work, but for now this works
OS X 10.7.3 (Lion x64) will play windows media video files through MPlayerX available through the Apple App Store. Two additional steps (1) make sure using the 32bit version even if on an x64 OS X and make sure the codecs are available.
Windows Media Video (WMV) is a series of video codecs and their corresponding video coding formats developed by Microsoft. It is part of the Windows Media framework. WMV consists of three distinct codecs: The original video compression technology known as WMV, was originally designed for Internet streaming applications, as a competitor to RealVideo. The other compression technologies, WMV Screen and WMV Image, cater for specialized content. After standardization by the Society of Motion Picture and Television Engineers (SMPTE),[1][2] WMV version 9 was adapted for physical-delivery formats such as HD DVD and Blu-ray Disc and became known as VC-1.[3][4] Microsoft also developed a digital container format called Advanced Systems Format to store video encoded by Windows Media Video.
In 2003, Microsoft drafted a video 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 as VC-1, thus making the WMV 9 format an open standard. VC-1 became one of the three video formats for the Blu-ray video disc, along with H.262/MPEG-2 Part 2 and H.264/MPEG-4 AVC.[3][4]
A WMV file uses the Advanced 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 .mw-parser-output .monospacedfont-family:monospace,monospace.asf file extension and not the .wmv file extension.[5][failed verification]
The ASF container can optionally support digital rights management 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.
Although WMV is generally packed into the ASF container format, it can also be put into the Matroska[6] container format (with file extension .mkv), or AVI container format (extension .avi). One common way to store WMV in an AVI file is to use the WMV 9 Video Compression Manager (VCM) codec implementation.[7][8]
Windows Media Video (WMV) is the most recognized video compression format within the WMV family. Usage of the term WMV often refers to the Microsoft Windows Media Video format only. Its main competitors are MPEG-4 AVC, AVS, RealVideo, and MPEG-4 ASP. The first version of the format, WMV 7, was introduced in 1999, and was built upon Microsoft's implementation of MPEG-4 Part 2.[9] Continued proprietary development led to newer versions of the format, but the bit stream syntax was not frozen until WMV 9.[10] While all versions of WMV support variable bit rate, average bit rate, and constant bit rate, WMV 9 introduced several important features including native support for interlaced video, non-square pixels, and frame interpolation.[11] WMV 9 also introduced a new profile titled Windows 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 as 720p and 1080p.
The Simple and Main profile levels in WMV 9 are compliant with the same profile levels in the VC-1 specification.[13] The Advanced Profile in VC-1 is implemented in a new WMV format called Windows Media Video 9 Advanced Profile. It improves compression efficiency for interlaced content and is made transport-independent, making it able to be encapsulated in an MPEG transport stream or RTP packet format. The format is not compatible with previous WMV 9 formats, however.[14]
WMV is a mandatory video format for PlaysForSure-certified online stores and devices, as well as Portable Media Center devices. The Microsoft 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 the Microsoft 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 in screencast 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 color palette.[18]
Windows Media Video Image (WMV Image) is a video slideshow 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. 30 frames per second at 1024 px 768 px resolution) requires heavy computer processing. The latest version of the format, WMV 9.1 Image, used by Photo Story 3, features additional transformation effects, but is not compatible with the original WMV 9 Image format.[20]
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 to MPEG-2 before burning a DVD (average file sizes in MPEG-2 are 5 to 6 times the .wmv file).
The audio format used in conjunction with Windows Media Video is typically some version of Windows Media Audio, or in rarer cases, the deprecated Sipro ACELP.net audio format. Microsoft recommends that ASF files containing non-Windows Media formats use the generic .ASF file extension.
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