Mac mini M1: Connect display via HDMI or USB-C?

[Foxer]

I picked-up a Mac mini and LG 4k HDR display (27UN850-w). The display has has connections for both USB-C and HDMI. Is there any reason to choose one over the other? FWIW, this is being used mainly for home office purposes, but I may watch the occasional movie.

And I do have the HDR "wash-out" situation that seems to be common here, but that doesn't seem to be at all effected by one connection or the other.

 

[joevt]

The USB-C ports use DisplayPort 1.4 which has more bandwidth (25.92 Gbps). It can do 4K 60Hz 10bpc RGB or 4:4:4.

Bandwidth is pixel clock multiplied by pits per pixel. 4K 60Hz is between 500 and 600 MHz (CVT-RB timing: 533.25 MHz; HDMI timing: 594 MHz). 533.25MHz x 30bpp = 16 Gbps.

HDMI 2.0b has less bandwidth (14.4 Gbps). HDMI 2.0b can do 4K 60Hz 8bpc RGB or 4:4:4. HDR requires 10bpc, in which case you need to use 4:2:2 or 4:2:0 chroma sub sampling. https://www.rtings.com/tv/learn/chroma-subsampling

 

[PBL_1]

You get more scaling options if you connect via USB-C.

 

[antwormcity]

One thing perhaps that comes in question - frame rate depends on your monitor electronics.

Not specifically your case, M1 systems are getting a lot of bad press for 30Hz only or whatever lag for gamers at high resolutions 4K/5K @10-bits 4:4:4. Most monitor electronics does not support 60Hz or newer HDMI/Display Port standards, they just pack a higher resolution panel, check the monitor manual as well. There is indeed a known issue with some higher end monitors and M1 compatibility and that HDR washout situation.

I'd say go with a single USB-C cable solution and if you have USB ports on your monitor, or audio ports you can seamlessly move it all there in the back of the display and reduce cable clutter + unused free ports on the mini. USB-C does have higher bandwidth also as pointed above.

 

[Feyl]

I have a similar monitor (LG 27UL850-W) and if you want to watch movies in 4K HDR you have to use HDMI with proper cable. With USB-C you're stuck at 1080p HDR only.

 

[antwormcity]

The LG offered DisplayHDR 400 seems more marketing to me. Here is the spec from VESA

First genuine entry point for HDR.

Significant step up from SDR baseline:

True 8-bit image quality – on par with top 15% of PC displays today
Global dimming – improves dynamic contrast ratio
Peak luminance of 400 cd/m2 – up to 50% higher than typical SDR
Minimum requirements for color gamut and contrast exceed SDR

Sounds like a monitor limitation to me not USB-C or M1