SMPTE 421M, informally known as VC-1, is a video coding format. Most of it was initially developed as Microsoft's proprietary video format Windows Media Video 9 in 2003. With some enhancements including the development of a new Advanced Profile, it was officially approved as an SMPTE video codec standard on April 3, 2006. The technology was developed with contributions from a number of companies, with the majority of patent contributions from Microsoft, Panasonic, LG Electronics, and Samsung Electronics.
VC-1 is supported in the now deprecated Microsoft Silverlight, the now-discontinued HD DVD, and in the Blu-ray Disc.
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 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.
VC-1 is supported in the PlayStation 3 console and the FFmpeg project also includes a VC-1 decoder.
On August 24, 2012, the Raspberry Pi Foundation announced hardware decoding support for VC-1.