VC-1 is an evolution of the conventional video codec design that is based on discrete cosine transform (DCT) and also found in H.261, H.263, MPEG-1, MPEG-2, and MPEG-4. It's an alternative to the MPEG-4 AVC (H.264) video codec standard.
VC-1 contains coding tools for interlaced video sequences and progressive encoding. The main goal of VC-1 development and standardization is to support the compression of interlaced content without first converting the content to progressive. This support makes VC-1 more attractive to broadcast and video industry professionals.
For information on how DirectX VA decodes VC-1, see DirectX Video Acceleration Specification for Windows Media Video v8, v9 and vA Decoding (Including SMPTE 421M "VC-1").