Chroma Subsampling

When digital video is encoded for display, rather than editing, it's usually stored in a compressed colorspace such as YV12 or YUY2. These colorspaces use Chroma Subsampling to compress each Frame by cutting the amount of U and V (chroma) detail to as little as 25% of the original uncompressed image.

Without Chroma Subsampling, the storage requirement for most consumer video formats, including HD DVD, Blu-ray, DVD, SVCD, VCD, AVCHD, HDV, and DV, would double.