As defined in ITU-R BT.601, digital luminance and color difference signal coding. Y is the luminance signal sampled at l3.5 MHz. Cr is the digitized version of the analog component (R-Y). Cb is the digitized version of (B-Y). The two color difference signals are sampled at 6.75 MHz. In the HD SMPTE 274M standard, sampling rates are 5.5 times greater.canonglossaryus
Terminology to describe the luminance (Y) and color difference signals (R-Y) and (B-Y) of component video. Y is luminance information and the R-Y and B-Y signals together provide the color information. These signals, derived from the original RGB source, are used in most video systems as a bandwidth reduction technique.