The color information compression in Sony's HDCAM high-definition digital Betacam videotape. In most subsampling, the two color signals are compressed, not the luma, and the luma is expressed as the first digit in the notation; for example, 4:2:2 and 4:2:0. HDCAM notation begins with the digit "3" because the luma is also compressed to 1440 pixels from 1920, and the chroma is one third the luma rate. See
chroma subsampling.