> They also split the signal in chroma and luma (basically colour and brightness, respectively) and then lowered the resolution of the chroma with the justification that the human eye is far more sensitive to differences in brightness than differences in colour.

It's worth mentioning that the split between chroma and luma wasn't for "compression" but so color signals were backwards compatible with black and white televisions. It's also why we use 29.97 fps instead of 30.[0]

[0]: http://glydeck.blogspot.com/2011/07/why-do-we-have-2997-fram...