Function color_standard 

fn color_standard(
    offered: &[VAProcColorStandardType],
    wanted: ColorDescription,
) -> VAProcColorStandardType

The color standard a video processor is told for wanted: the explicit one where the driver takes it, since the properties then say everything; else the standard whose matrix, transfer, and primaries come closest, weighted four, two, and one, or none when nothing matches at all.