CAC-2504 Compatibility with DP 1.2

Updated on 15-09-2021 in USB Type C
3 on 15-09-2021

I have a 2017 Kaby Lake MacBook Pro with Iris Plus Graphics 640. Will CAC-2504 let me output 4K HDR to a television?

I often see people say that DP 1.2 doesn’t support HDR. Where is this information coming from?

Based on the Intel white paper for Kaby Lake, it seems that Kaby Lake supports HDR through both DP and HDMI 2.0 w/ LSPCON. As far as I know, Kaby Lake does not support DP above 1.2.

A user on the Intel forum e-mailed VESA about this and received the following response:

The VESA representative had personally done HDR through DP 1.2 with Intel graphics.

In my personal experience, my Dell U2720Q has displayed an HDR signal when connected with DP Alt Mode 1.2 to my MacBook. I have successfully used it to watch HDR YouTube videos and local content.

Has anyone tested the combination of 2017 MacBook Pro with CAC-2504 before? Or if you feel that there are any problems with the conclusions that I’ve drawn above, I would appreciate it if you would let me know.

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2 on 15-09-2021

I’m not sure how the difference between DisplayPort 1.2 and DisplayPort 1.4 affects HDR. The DisplayPort 1.2 spec can be found on the internet but doesn’t mention HDR. The DisplayPort 1.4 spec cannot be found.

Somehow, Apple enables HDR for connections made to Intel graphics (iGPU). I have a Mac mini 2018 with Intel UHD Graphics 630 which can do HDR from Thunderbolt (iGPU DisplayPort 1.2 connected -> Titan Ridge Thunderbolt controller) and HDMI (iGPU DisplayPort 1.2 -> MegaChips MCDP2920A4 DisplayPort 1.4 to HDMI 2.0b). I can’t say how well it appears since I’m not a HDR expert. I can only say if macOS makes the HDR option available and when my display indicates that it detects an HDR input.

I don’t know the difference between a static and dynamic HDR signal and an SDR signal. Maybe Apple is using static HDR signal. They could setup the GPU to output the necessary stuff for HDR even without DisplayPort 1.4 features (maybe the only thing missing from DisplayPort 1.4 is HBR3 and DSC and some other stuff not necessary for static HDR).

macOS can allow DisplayPort to HDMI adapters that support HDR to get HDR from iGPU.

Some adapters may require a firmware update to get HDR support in macOS (Club 3D CAC-1080, Club 3D CAC-1085, Cable Matters 201388).

Some adapters, such as the CAC-1080, can do HDR from iGPU at 4K60.

Some adapters, such as the CAC-1085 and Cable Matters 201388, may only work at 4K30 if DisplayPort 1.4 is not supported (maybe because DisplayPort 1.2 can’t do 4:2:0 and the adapter doesn’t do RGB/4:4:4 to 4:2:0 conversion or maybe they need another firmware update to enable that?).

I’m not sure what category the CAC-2504 is in since I don’t have one. I would guess it’s in the CAC-1080 category. It would be helpful if Club-3d listed what chip was used in each adapter (and their latest firmware version if they have an updater for it).

The CAC-1586 is probably similar to the CAC-1085?

The CAC-1504 is probably similar to the CAC-1070/CAC-2070?

Maybe Club-3d should group adapters by chip/capability instead of connector so I don’t get the USB-C version if I already have the DisplayPort version.


on 15-09-2021

In this thread:

a Club 3D employee says that CAC-2504, CAC-1180, and CAC-1080 all use MegaChips MCDP2900. So should the CAC-2504 be able to work in my case?

It’s not clear, but did you buy a Club 3D product to go from DP 1.2 to HDMI 2.0? If so, which product corresponds with MegaChips MCDP2920A4?

on 15-09-2021

Never mind, I see that the MCDP2920 is pre-installed in the Mac Mini. I also see from your MacRumors post that CAC-1080 and CAC-1085 work for HDR after getting a firmware update from Club 3D support. I am going hope that the CAC-2504 works for me.

Thank you for your help.

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