USB-C Dock: HDMI 2.0 and HDR?

[childoftheko4n]

Hey all, apologies if this has been answered a million times. However, if I run a dock like this:OWC Travel Dock and connect my monitor to the dock, and the dock to my MBP via the USB-C port, why doesn't HDR enable anymore? The monitor has it (and works if I plug the HDMI cord into my MBP directly), and the dock is HDMI 2.1, I know I am missing something obvious, but what is it? The conversion of the monitor from HDMI through USB-C?


*it looks like HDR is back as an option if I step the refresh rate down to 120 or below

Thanks!

 

[joevt]

The dock is HDMI 2.0, not HDMI 2.1 but that shouldn't matter for HDR.

What MBP?

What display?

What resolution and refresh rate?

Does the dock support HBR3 link rate? Does the dock support DSC? Connect it to an Intel Mac, connect a display, and run AllRez to find out.
The dock supports USB 3.x so it must be limited to a link width of 2 lanes.

HDR usually requires a mode that supports 10bpc.

4K60 = 523 - 594MHz.
On the HDMI side, 10bpc requires 4:2:2 or 4:2:0 chroma sub sampling.
On the DisplayPort side, with only two lanes, 10bpc requires DSC, or HBR2 4:2:0 (< 576MHz), or HBR3 4:2:2.

But you said refresh rate 120 which means you are probably using a lower resolution such as 1440p or 1080p.
1440p120 = 483 - 497MHz. On the DisplayPort side, with only two lanes, 10bpc requires DSC, HBR2 4:2:0, or HBR3 4:2:2
1080p120 = 275 - 285MHz. On the DisplayPort side, with only two lanes, 10bpc requires only HBR2.

I am thinking that DSC is probably not supported by default in macOS even if the dock supports DSC.

The CalDigit SOHO dock supports HBR3 x2 with DSC, but macOS doesn't enable DSC automatically except in Catalina. The MST hub used in the CalDigit SOHO doesn't appear to support 10bpc with DSC which makes DSC kind of useless unless you don't care about 10bpc or HDR.

 

[childoftheko4n]

The dock is HDMI 2.0, not HDMI 2.1 but that shouldn't matter for HDR.

What MBP?

What display?

What resolution and refresh rate?

Does the dock support HBR3 link rate? Does the dock support DSC? Connect it to an Intel Mac, connect a display, and run AllRez to find out.
The dock supports USB 3.x so it must be limited to a link width of 2 lanes.

HDR usually requires a mode that supports 10bpc.

4K60 = 523 - 594MHz.
On the HDMI side, 10bpc requires 4:2:2 or 4:2:0 chroma sub sampling.
On the DisplayPort side, with only two lanes, 10bpc requires DSC, or HBR2 4:2:0 (< 576MHz), or HBR3 4:2:2.

But you said refresh rate 120 which means you are probably using a lower resolution such as 1440p or 1080p.
1440p120 = 483 - 497MHz. On the DisplayPort side, with only two lanes, 10bpc requires DSC, HBR2 4:2:0, or HBR3 4:2:2
1080p120 = 275 - 285MHz. On the DisplayPort side, with only two lanes, 10bpc requires only HBR2.

I am thinking that DSC is probably not supported by default in macOS even if the dock supports DSC.

The CalDigit SOHO dock supports HBR3 x2 with DSC, but macOS doesn't enable DSC automatically except in Catalina. The MST hub used in the CalDigit SOHO doesn't appear to support 10bpc with DSC which makes DSC kind of useless unless you don't care about 10bpc or HDR.

2021 MBP 14 - M1 Pro
LG 27GP850-B
2560x1440p - it goes up to 144hz and when plugged into the MBP direct, you can do 144hz + HDR. when through the dock you can do HDR at 120 or 60hz, but not 144hz (really doesn't matter, not gaming on this computer, more so just curious)

its natively 1440p 144hz. When plugged in directly it runs native resolution / refresh and HDR. when through the dock (same HDMI cable) it supports HDR at the stepped down refresh, but still native 1440p.

 

[joevt]

Can't know what's going on without the extra info. At least you can try extracting the EDID using SwitchResX. That should show the pixel clocks that get used for the 144 and 120Hz modes.
If you don't have an Intel Mac, then AllRez can at least list all the modes and show which timing is currently used.

 

[childoftheko4n]

its an M1 mac as listed above. I will try and get the other stats when home, but no biggie. was more so just curious but if its lots of extra digging im not too concerned about running 120 vs 144.