YCbCr

YCbCr, Y′CbCr, or Y Pb/Cb Pr/Cr, also written as YC_BC_R or Y′C_BC_R, is a family of color spaces used as a part of the color image pipeline in video and digital photography systems. Y′ is the luma component and C_B and C_R are the blue-difference and red-difference chroma components. Y′ (with prime) is distinguished from Y, which is luminance, meaning that light intensity is nonlinearly encoded based on gamma corrected RGB primaries.

Y′CbCr color spaces are defined by a mathematical coordinate transformation from an associated RGB primaries and white point. If the underlying RGB color space is absolute, the Y′CbCr color space is an absolute color space as well; conversely, if the RGB space is ill-defined, so is Y′CbCr. The transformation is defined in equations 32, 33 in ITU-T H.273. Nevertheless that rule does not apply to P3-D65 primaries used by Netflix with BT.2020-NCL matrix, so that means matrix was not derived from primaries, but now Netflix allows BT.2020 primaries (since 2021).^[1] The same happens with JPEG: it has BT.601 matrix derived from System M primaries, yet the primaries of most images are BT.709.