Chroma subsampling explained

The short explanation

Video is stored as brightness plus color. 4:4:4 keeps full color detail for every pixel. 4:2:2 halves the horizontal color resolution. 4:2:0 halves it both horizontally and vertically, and needs roughly half the bandwidth of 4:4:4.

Where you run into it

For film and television the difference is close to invisible — almost all broadcast, streaming and disc content is delivered in 4:2:0 anyway, so sending it as 4:4:4 gains nothing.

For a computer it is very visible. Fine colored text on a 4:2:0 signal develops colored fringes and looks smeared. That is why PC users chase 4:4:4 and why televisions often need a specific input setting before they accept it.

Subsampling is also the lever that makes demanding modes possible: 8K60 fits uncompressed at 4:2:0 but not at 4:4:4, for exactly this reason.

How the DR HDMI 8K handles it

Its EDID tables let you advertise a specific chroma explicitly — 4K120 4:4:4 or 4K120 4:2:0, 4K60 4:4:4 at 600MHz or 4K60 4:2:0 at 12-bit. Rather than hoping the chain lands on 4:4:4, you tell the source which one is available. The DR HDMI 8K also shows the chroma declared in the input and output EDID on its OLED, so you can confirm what the source is being offered.