Pairing ProMotion Mac with Studio Display?

[joevt]

Any idea on what those reasons might be?

Extra cost in developing the solution?
Has any one connected a DSC display that uses more than HBR2 to a Mac yet?

Even if they could build a dual-tile display that requires DSC to be used with TB3/4, might Apple not want to build it for visual-quality reasons?

DSC is supposed to be visually lossless. Apple uses it on XDR and Studio display. No-one has complained about visual-quality issues with DSC. Has anyone tried doing a comparison of DSC and non-DSC? The issue (if any) can't be seen as easily as with compression from chroma sub sampling 4:2:0.

For instance, they could have driven the XDR without having to bother with dual-tile HBR3 if they had used DSC, yet they chose not to. Could that have been because they thought DSC might interfere with critical color-grading work? [Not that the monitor is quite capable of that—it doesn't meet Dolby Vision certification requirements for use as an HDR mastering monitor—but that may have been Apple's aspiration when they designed it.]

XDR uses HBR2 + DSC for GPUs that have DSC.
XDR uses dual HBR3 for GPUs that don't have DSC.
The former allows writing to USB devices at 5 Gbps. The latter will only allow writing to USB devices at USB 2 speed (480 Mbps) or maybe 1 Gbps (I haven't seen anyone test this).

 

[theorist9]

XDR uses HBR2 + DSC for GPUs that have DSC.

Since that would include all AS devices, that would indeed say that Apple is fine with DSC.

But how do you know that AS devices use DSC even when directly connected to an XDR? Are you able to measure the link rate, or see a DSC flag? And what about the Dell 6k?

Has any one connected a DSC display that uses more than HBR2 to a Mac yet?

I don't know. Does anyone make an 8k60 or 4k240 display that can be driven with a single cable using DP 1.4? Those would have to use DSC—and I'm guessing they would use HBR3 rather than HBR2, to avoid high compression.

[The Samsung Odyssey Neo G8 is 4k240 and can be driven from a single TB port, but it requires DP 2.1.]

8k@60 with single-tile HBR3 and DSC has been part of part of the DP standard since v. 1.3:

DisplayPort explained

tripplite.eaton.com

And some PC video cards do support 8k@60 with single-tile HBR3 and DSC:

Dell Systems Supporting HBR3 Specifications | Dell US

 

[joevt]

Since that would include all AS devices, that would indeed say that Apple is fine with DSC.

But how do you know that AS devices use DSC even when directly connected to an XDR? Are you able to measure the link rate, or see a DSC flag? And what about the Dell 6k?

You can see the DSC info for Intel Macs using my allrez utility or AGDCDiagnose.

For Apple Silicon Macs, you can get a list of display modes and a list of color modes for each mode but I don't know how to get the current color mode for the current display mode.

The displays modes have a flag that indicates if it's a tiled mode. That should be sufficient. You could also check the pixel clock to see if it matches that of a mode in the EDID that requires DSC.

There's a script at:
https://gist.github.com/joevt/e862b0088ef58b9144877d01401bcee8
A slower version of the script:
https://gist.github.com/joevt/0c75b42171b3fb1a5248b4e2bee8e4d0
Allrez:
https://github.com/joevt/AllRez

I don't know. Does anyone make an 8k60 or 4k240 display that can be driven with a single cable using DP 1.4? Those would have to use DSC—and I'm guessing they would use HBR3 rather than HBR2, to avoid high compression.

[The Samsung Odyssey Neo G8 is 4k240 and can be driven from a single TB port, but it requires DP 2.1.]

8k@60 with single-tile HBR3 and DSC has been part of part of the DP standard since v. 1.3:

View attachment 2335939

DisplayPort explained

tripplite.eaton.com

And some PC video cards do support 8k@60 with single-tile HBR3 and DSC:

Dell Systems Supporting HBR3 Specifications | Dell US

I think DSC is new to DP 1.4. That page says as much so I don't know why they mention DSC in the DP 1.3 row of the table. Well, 4:2:0 could be used instead of DSC to get 12bpp (using 8bpc).

There are probably plenty of HBR3 displays with DSC. The question is whether Apple allows them to work with macOS.
Here's one instance including an allrez dump but it's on an Intel Mac. The mode is 3840x2160@150Hz 1329MHz HBR3 x4 using DSC@12bpp.
https://forums.macrumors.com/thread...icon-m1-m2-now-possible.2381664/post-32254316
HBR2 x4 should be able to do up to 1440MHz@12bpp (if there is no FEC) so the display maybe doesn't need HBR3 to get 1329MHz. HBR3 is useful for getting 4K120 if you don't have DSC and don't need HDR.

Here's another example on an Intel Mac. It's a 5K display, only 966.49MHz and uses DSC with HBR3. But it also has a tiled mode in case you don't have DSC. The HBR3 helps for when you don't have two DisplayPort outputs for tiled mode.
https://forums.macrumors.com/threads/diy-5k-monitor-success.2253100/post-29006429
This was running on Catalina. DSC goes away in Big Sur. Maybe it returns in Sonoma?