SMPTE ST 421 – VC-1 Compressed Video Bitstream Format and Decoding Process

This document defines the bitstream syntax and semantics for compressed video data in VC-1 format, and specifies constraints that are required for conformant bitstreams. It also describes the complete process required to decode the bitstream. The compression algorithm is not specified in this standard. The video formats supported by VC-1 include progressive and interlaced video sampled in the form of Y luma samples and Cb, Cr color-difference in 8-bit per component sample values resulting from a 4:2:0 sampling grid. The decoding process outputs 8-bit per component video samples corresponding to the original 4:2:0 sampling grid. The display rendering process by which decoded Y, Cb, Cr samples are converted to a visible image or to a video output signal in a complete decoding system or device are not specified in VC-1. A VC-1 bitstream may convey additional metadata and user data which shall be accounted for in the buffer model. Metadata included in VC-1 streams is not used by the decoding process, but is passed to the display rendering process for the identification and reconstruction of the sampled video format, sample aspect ratio, color space, etc.

This revision corrects typographical errors and provides clarifying text to support correct interpretation of the standard as described in Amendment 1-2007 to SMPTE 421M-2006 and in Amendment 2:2011 to SMPTE 421-M:2006.

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