Chroma subsampling 4:4:4 vs 4:2:0. See it.
Most video streams keep one colour for every four pixels. 4:4:4 keeps them all.
One colour per pixel, or one for four.
Brightness stays sharp in all three. 4:2:2 and 4:2:0 share only the colour.
4:4:4
Every pixel has its own colour.
4:2:2
Two pixels side by side share one.
4:2:0
Blocks of four share one.
Where you see it.
Left 4:4:4, right 4:2:0, simulated.
Red playheads
Thin red lines fade.
Names in chat
Coloured names go muddy.
Hairlines and coloured type
Fine lines and small text lose their colour.
Test your own setup.
Show the test image pixel for pixel on the computer you share, and view it unscaled on the other. Magenta and green: 4:4:4. Grey: 4:2:0 or scaled.
See it on your own screens.
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