VC-1

SMPTE 421M, informally known as VC-1, is a video coding format. It was initially developed as the proprietary video format Windows Media Video 9 by Microsoft in 2003 and officially approved as a SMPTE video codec standard on April 3, 2006.

It is today a supported standard found in Blu-ray Discs, Microsoft's Silverlight framework, and the now-discontinued HD DVD.

VC-1 is an evolution of the conventional DCT-based video codec design also found in H.261, MPEG-1 Part 2, H.262/MPEG-2 Part 2, H.263, and MPEG-4 Part 2. It is widely characterized as an alternative to the 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 Advanced Profile development and standardization was to support the compression of interlaced content without first converting it to progressive, making it more attractive to broadcast and video industry professionals.

Both HD DVD and Blu-ray Disc have adopted VC-1 as a 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 some related components needed for playback of VC-1 encoded HD DVD movies.

Microsoft has designated VC-1 as the Xbox 360 video game console's official video format, and game developers may use VC-1 for full motion video included with games. By means of an October 31, 2006 update, all formats of Windows Media Video could be played on the Xbox 360 from a disc, USB storage device, or streaming from a PC via Windows Media Connect/Windows Media Player 11.

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