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Windows Media 9 Video Codec; SMPTE VC-1

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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 Video Codec; SMPTE 421M-2006. Standard for Television: VC-1 Compressed Video Bitstream Format and Decoding Process
Description

Video bitstream produced by the Windows Media 9 video codec. According to the Wikipedia VC-1 article (consulted May 7, 2010), "the codec is an evolution of the conventional DCT-based video codec design also found in H.261, H.263, MPEG-1, MPEG-2, and MPEG-4. It is widely characterized as an alternative to the latest ITU-T and MPEG video codec standard known as H.264/MPEG-4 AVC. VC-1 contains coding tools for interlaced video sequences as well as progressive encoding. The main goal of VC-1 development and standardization is to support the compression of interlaced content without first converting it to progressive, making it more attractive to broadcast and video industry professionals."

There are a variety of profiles and levels for VC-1; these are described in the Wikipedia VC-1 article and by Microsoft. See also Notes below.

Production phase Generally used in files that represent a final-state format for end-user delivery.
Relationship to other formats
    Other Identical to the SMPTE standard VC-1
    Has subtype Various profiles, not documented at this Web site at this time
    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 Decoding specification is an open standard from SMPTE. The codec was developed by Microsoft and other companies.
    Documentation SMPTE 421M-2006. Standard for Television: VC-1 Compressed Video Bitstream Format and Decoding Process.
Adoption

According to the Wikipedia VC-1 article (consulted April 28, 2010), "Both HD DVD and Blu-ray Disc have adopted VC-1 as a mandatory video standard, meaning their video playback devices will be capable of decoding and playing video-content compressed using VC-1. Windows Vista partially supports HD DVD playback by including the VC-1 decoder and related components needed for playback of VC-1 encoded HD DVD movies. The FFmpeg project is working on a free implementation of this codec.

"Microsoft has designated VC-1 as the Xbox 360 video game console's official video codec, and game developers may use VC-1 for full motion video included with games. By means of an October 31, 2006 update, people can now play all formats of Windows Media Video on the Xbox 360 from a disc, USB storage device, or streaming from their PC via Windows Media Connect/Windows Media Player 11. This allows anyone to play VC-1 encoded files on the console."

In 2004, AtomFilms began using Windows Media High-Definition Video at 720p resolution for their high definition service and this usage continued at least through May 2010. See 2004 press release via Internet Archive. AtomFilms was absorbed into Comedy Central in 2012.

    Licensing and patents According to the Wikipedia VC-1 article (consulted April 28, 2010), "Although widely considered to be Microsoft’s product, there are actually fifteen companies in the VC-1 patent pool (as of August 17, 2006). As an SMPTE standard, VC-1 is open to implementation by anyone, although implementers are hypothetically required to pay licensing fees to the MPEG LA, LLC licensing body or directly to its members, who claim to hold essential patents on the format (since it is a non-exclusive licensing body)."
Transparency Depends upon algorithms and tools to read; will require sophistication to build tools.
Self-documentation Pertains to the file format; see ASF, the wrapper class that includes the WMV file format.
External dependencies None
Technical protection considerations Pertains to the file format; see ASF, the wrapper class that includes the WMV file format.

Quality and functionality factors Explanation of format description terms

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

Varies according to profile and level, from moderate to very good; capable of compressing High Definition signals. See profile and level informatio for VC-1 in the Wikipedia VC-1 article and by Microsoft.

In earlier descriptions, as of 2004, information along the following lines was being provided. From the codecs page at the Microsoft Windows Media web site: "This codec provides a quality enhancement . . . compared with Windows Media Video 8 (the highest gains occur at higher bit rates). A file containing Windows Media Video 9-based content is typically only half the size of an MPEG-4 file of comparable quality." WMV9 offers variable bit rate encoding that provides "optimal quality with a lower average bit rate and file size." As of 2004, higher quality was said to be provided by WMV9_PRO but this seems to have been changed by the establishment of VC-1 and the associated set of profiles and levels; see the Wikipedia VC-1 article and an information page from Microsoft.

Functionality beyond normal rendering Not applicable
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 April 28, 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 a more recent and fully compliant 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 equivalent or comparable quality to MPEG-2. The Windows Media Video 9 Advanced Profile codec also offers this same improvement in encoding efficiency with interlaced contents. A decoder for WVC1 is included in Windows Media Player 11, which is bundled with Windows Vista and is available as a download for Windows XP."

Additional information on Windows Media codecs and software is available at the Microsoft Web site.

History  

Format specifications Explanation of format description terms


Useful references

URLs


Last Updated: 02/21/2017