Y'CbCr is the color space defined by ITU-R BT.601. Y' is the luma component and the Cb and Cr components are color difference signals. The technically-correct notation is Y'Cb'Cr' since all three components are derived from R'G'B. Many people use the YCbCr notation rather than Y'CbCr or Y'Cb'Cr'.

4:2:2 Y'CbCr means that Y' has been sampled at 13.5 MHz, while Cb and Cr were each sampled at 6.75 MHz. Thus, for every two samples of Y', there is one sample each of Cb and Cr.

4:1:1 Y'CbCr means that Y' has been sampled at 13.5 MHz, while Cb and Cr were each sampled at 3.375 MHz. Thus, for every four samples of Y', there is one sample each of Cb and Cr.