why do 4k video look “more clean” than videos in 1080p, on the same exact monitor.
(maybe it’s just mine, i have an asus monitor)
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Depending on the source, higher bitrate video may use a different codec. For example H264 is only a standard in TV broadcasts to 1080p, then they switch to H265 for 4k. This gives it a generational quality boost in the video codec. Some hardware video players, even if capable of 4k, can’t play H264 above 1080p.
If that’s not the situation (eg: youtube), it’s still typical to give higher bitrates to 4k than to 1080p. It turns out video bitrate is a major defining factor in image quality, and just generally more bits is better for image quality even when the resolution changes alongside it.
And finally, digital video is compressed in one special way. Rather than sending the image as Red, Green and Blue layers, it’s sent as a brightness layer, and 2 colour layers. It’s sorta like how in photoshop and other image editing tools you can select a colour as hue, saturation and luminosity, but not quite the same. The twist is, the 2 colour layers are actually half-width and half-height of the actual image size – the brightness layer is full resolution. This means that in any 2×2 group of pixels (aligned on the main 2×2 grid) are all the same basic colour, and only vary in brightness from black to a nice bright red, orange, yellow, green, etc.
This means when you take a 4k image and compress it, you get 1080p resolution colour layers. This can provide that very small subtle quality improvement because it gives each 1080p scaled pixel its own unique colour.
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