Sustainability of Digital Formats: Planning for Library of Congress Collections

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Windows Media 9 Professional Video Codec

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Format Description Properties Explanation of format description terms

Identification and description Explanation of format description terms

Full name Windows Media 9 Professional Video Codec
Description

Video bitstream produced by the Windows Media 9 professional video codec.

This format description seems to have been overtaken by events. During 2005, the Microsoft Web site stopped referring to a "professional" codec and instead began promoting an Advanced Profile with features tailored to high definition video content (see Notes below). During 2006, however, SMPTE finalized the VC-1 standard (421M), thus placing the Microsoft video codec family more in the mainstream. At the same time, a number of profiles and levels were established; for example, see the Wikipedia VC-1 article and this Microsoft information page. At this Library of Congress Web site, the VC-1 connection is highlighted in the description of WMV9, the fundamental Windows Media video codec. Comments on the best way to elucidate this topic are welcome.

Production phase Generally used in files that represent a final-state format for end-user delivery.
Relationship to other formats
    Used by WMV_WMV9, Windows Media Video file with WMV9 codec

Local use Explanation of format description terms

LC experience or existing holdings  
LC preference See WMV

Sustainability factors Explanation of format description terms

Disclosure Proprietary. Developed by Microsoft.
    Documentation Specifications not disseminated.
Adoption Extent of adoption is not known.
    Licensing and patents See ASF for link to pages covering licensing of Windows Media and the Advanced Systems Format.
Transparency Depends upon algorithms and tools to read; will require sophistication to build tools.
Self-documentation Not applicable
External dependencies None
Technical protection considerations Not applicable

Quality and functionality factors Explanation of format description terms

Moving Image
Normal rendering Good support.
Clarity (high image resolution)

Moderate to excellent, considering this is a compression algorithm, varies according to level selected.

The Microsoft Windows Media web site codecs page is regularly edited and updated (see links listed in Useful references below); in 2004, the text included this note: "For content that requires ultra-high video quality. Windows Media Video 9 Professional defines profiles of the Windows Media Video 9 codec that are automatically applied at higher bit rates and resolutions. Its efficiency can bring high-definition quality to computer users, enabling storage and delivery of a complete movie at 720p resolution (1280 x 720 pixels per frame), with 5.1 digital discrete channel surround sound, on a single standard DVD. In the near future, hardware acceleration of decoding will also make playback of both 720p and 1080p content possible even on midrange Pentium 4 class computers." WMV9_PRO offers variable bit rate encoding that provides "optimal quality with a lower average bit rate and file size."

In 2005, the as-then-updated codecs page stated the following regarding the Advanced Profile: "This is a new codec that is included with Windows Media Player 10, the Windows Media Format 9.5 SDK, and the updated codec installation packages. Key features of Windows Media Video 9 Advanced Profile include improved interlaced support and transport format independence." See also Notes below.

Regarding the professional codec, one user reported in 2004 that he produced constant-bitrate test footage at different bitrates, noticed that 20 Mb/s seemed to be the upper limit offered by the software, and said that he was unable to discern incremental improvements as the bitrate rose above 4 Mb/s. (Private communication.)

Functionality beyond normal rendering

The Microsoft Windows Media web site codecs page is regularly edited and updated (see links listed in Useful references below); in 2005, the text stated the following regarding the Advanced Profile: "Transport format independence enables the delivery of Windows Media Video 9 Advanced Profile over systems that are not Windows Media-based, such as standards-based broadcast infrastructures (through native MPEG-2 transport streams), wireless infrastructures (through RTP), or even DVDs. This feature incorporates Windows Media Video 9 Advanced Profile as a next-generation compression technology into emerging standards initiatives, such as those in SMPTE, DVB, ATSC and the DVD-Forum." See also Notes below.

Sound
Fidelity (high audio resolution) Presumably, producers can select WMA compression codecs; their fidelity capabilities are assessed at WMA9 and WMA9_PRO.
Multiple channels See WMA9 and WMA9_PRO

File type signifiers and format identifiers Explanation of format description terms

Tag Value Note
Filename extension Not applicable.   
Internet Media Type Not applicable.   
Magic numbers Not applicable.   

Notes Explanation of format description terms

General

According to the Wikipedia VC-1 article (consulted May 26, 2010): "WMVA was the original implementation of WMV Advanced Profile prior to the acceptance of the VC-1 draft by SMPTE. The codec was distributed with Windows Media Player 10 and Windows Media Format SDK 9.5 install packages. There are slight bitstream differences between WMVA and WVC1, so consequently WMVA is handled by a different DirectShow decoder than WVC1. Some 3rd party hardware and software decoders only decode WMVA based content. As of 2006, WMVA is considered a deprecated codec because it is not fully VC-1 compliant."

WVC1, also known as Windows Media Video 9 Advanced Profile, implements the Advanced Profile of the VC-1 codec standard. It offers support for interlaced content and is transport independent. With the previous version of the Windows Media Video 9 Series codec, users could deliver progressive content at data rates as low as one-third that of the MPEG-2 codec and still get the same quality as MPEG-2. The Windows Media Video 9 Advanced Profile codec also offers this same improvement in encoding efficiency with interlaced contents."

History  

Format specifications Explanation of format description terms


Useful references

URLs


Last Updated: 02/21/2017