What is bit depth?

In plain language

8-bit gives 256 levels per colour channel, 10-bit gives 1024 and 12-bit gives 4096. More levels means smoother gradients — and more data: 10-bit costs about 25% more bandwidth than 8-bit, 12-bit about 50%.

Why it matters in your setup

For standard dynamic range, 8-bit is usually enough. HDR is where it stops being enough: stretching a wider brightness range across only 256 steps produces obvious banding in skies and dissolves, so HDR content is mastered at 10-bit.

Bit depth also competes with everything else for bandwidth. 4K120 at 4:4:4 is specified at 10-bit rather than 12 for exactly that reason. If you push bit depth up, something else — chroma or frame rate — has to come down.

One quirk worth knowing: 4:2:2 signals are always processed at 12-bit and never clipped, which is why specifications say “up to 12-bit” rather than listing it separately.

What the DR HDMI 8K does with it

The DR HDMI 8K supports 4K at 10, 12 and 16-bit, up to 48-bit deep colour overall, and its EDID library lets you advertise a specific bit depth: 4K120 4:4:4 at 10-bit, 4K60 4:2:0 at 12-bit, 1080p at 12-bit or 8-bit. The OLED reports the colour depth actually negotiated.