Sustainability of Digital Formats
Planning for Library of Congress Collections
Sustainability of Digital Formats
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| Introduction | Sustainability Factors | Content Categories | Format Descriptions | Contact | |
| 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 November 28, 2006), "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 |
| LC experience or existing holdings | |
| LC preference | See WMV |
| 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. Additional information from Microsoft describes the status of the standard and provides information about software development kits. |
| Adoption | According to the Wikipedia VC-1 article (consulted November 28, 2006), "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 will partially support 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. On a update done on October 31, 2006, 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." |
| Licensing and patent claims | According to the Wikipedia VC-1 article (consulted November 28, 2006), "Although widely considered to be Microsoft's product, there are actually 15 companies in the VC-1 patent pool (as of 17 August 2006). As a 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 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. |
| Normal rendering | Good support. |
| Clarity (support for high image resolution) | Varies according to profile and level; can be very high, 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. 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. |
| Fidelity (support for high audio resolution) | Presumably, producers can select WMA compression codecs; their fidelity capabilities are assessed at WMA9 and WMA9_PRO. |
| Support for multiple sound channels | See WMA9 and WMA9_PRO. |
| Functionality beyond normal rendering | Not applicable |
| Tag type | Value | Note |
| Filename Extension | Not applicable | |
| Internet Media Type | Not applicable | |
| Magic numbers | Not applicable |
| General | According to the Wikipedia VC-1 article (consulted November 28, 2006), "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 |
URLs
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• SMPTE 421M-2006. Standard for Television: VC-1 Compressed Video Bitstream
Format and Decoding Process.
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