M1 Mac Mini missing 4k@120Hz and DDC/CI support

[Ronal]

o I totally forgot to mention I am running 27gn950 and it has dsc

 

[joevt]

o I totally forgot to mention I am running 27gn950 and it has dsc

Just FYI: According to the EDIDs at linuxhw/EDID on github
That display advertises a max dot clock of 1340 MHz which is greater than DisplayPort 1.4 can allow without DSC or chroma sub sampling (but it does support 4:2:2 so it could work without DSC).

It has this max timing:

    DTD:  3840x2160  143.999 Hz  16:9   332.062 kHz 1328.250 MHz (aspect 16:9, no 3D stereo, preferred)
               Hfront   48 Hsync  32 Hback  80 Hpol P
               Vfront    3 Vsync   5 Vback 138 Vpol N

 

[Ronal]

Just FYI: According to the EDIDs at linuxhw/EDID on github
That display advertises a max dot clock of 1340 MHz which is greater than DisplayPort 1.4 can allow without DSC or chroma sub sampling (but it does support 4:2:2 so it could work without DSC).

It has this max timing:

    DTD:  3840x2160  143.999 Hz  16:9   332.062 kHz 1328.250 MHz (aspect 16:9, no 3D stereo, preferred)
               Hfront   48 Hsync  32 Hback  80 Hpol P
               Vfront    3 Vsync   5 Vback 138 Vpol N

Sorry I’m not that technical, so is it better to run with dsc or without dsc?

 

[joevt]

Sorry I’m not that technical, so is it better to run with dsc or without dsc?

DSC is a method to reduce bandwidth. Other methods include:

1) reducing the resolution
2) reducing the frame rate
3) reducing the number of bits per component.
4) reducing the number of color components (use chroma sub sampling 4:2:2 or 4:2:0 instead of 4:4:4),

Components (three per pixel) are RGB or YCbCr. Chroma sub sampling requires YCbCr.
bpp = bits per pixel
bpc = bits per component

Chroma subsampling is a dumb method of compression. It throws away info from every 2nd pixel (or each pair of pixels shares their color info) horizontally (and vertically in the case of 4:2:0).

DSC is a smarter method of compression. It uses more info than chroma sub sampling to produce better compression.

The best images have
1) higher bits per component (at least 10 bpc for smoother gradients and HDR - another way to smooth gradients or reduce banding is to use dithering but that adds noise to the image)
2) use RGB or 4:4:4 (no chroma sub sampling)
3) don't use DSC.

But if you want more pixels per image (resolution) or more images per second (refresh rate) then you may have to use one of the methods to reduce bandwidth. Probably the best option to use is DSC because it is a visually lossless method of compression which can effectively triple the bandwidth (chroma sub sampling can only double the bandwidth). DSC can convert 36 bpp (12 bpc) to 12 bpp. DSC should be able to convert 30 bpp to 8 bpp but I don't know if macOS allows it.

 

[Ronal]

DSC is a method to reduce bandwidth. Other methods include:

1) reducing the resolution
2) reducing the frame rate
3) reducing the number of bits per component.
4) reducing the number of color components (use chroma sub sampling 4:2:2 or 4:2:0 instead of 4:4:4),

Components (three per pixel) are RGB or YCbCr. Chroma sub sampling requires YCbCr.
bpp = bits per pixel
bpc = bits per component

Chroma subsampling is a dumb method of compression. It throws away info from every 2nd pixel (or each pair of pixels shares their color info) horizontally (and vertically in the case of 4:2:0).

DSC is a smarter method of compression. It uses more info than chroma sub sampling to produce better compression.

The best images have
1) higher bits per component (at least 10 bpc for smoother gradients and HDR - another way to smooth gradients or reduce banding is to use dithering but that adds noise to the image)
2) use RGB or 4:4:4 (no chroma sub sampling)
3) don't use DSC.

But if you want more pixels per image (resolution) or more images per second (refresh rate) then you may have to use one of the methods to reduce bandwidth. Probably the best option to use is DSC because it is a visually lossless method of compression which can effectively triple the bandwidth (chroma sub sampling can only double the bandwidth). DSC can convert 36 bpp (12 bpc) to 12 bpp. DSC should be able to convert 30 bpp to 8 bpp but I don't know if macOS allows it.

Thanks for the detailed explanation, very informative

 

[s_muxiu]

Update here everyone, I have just updated my macOS Monterey and I found something in my Display setting panel which I uploaded below:

It seems that I can set my XV273K with Variable Refresh Rate, just like ProMotion feature?

 

[Krevnik]

Yes. Apple did have talks at WWDC about supporting AdaptiveSync (VRR) in macOS 12.

 

[joevt]

Update here everyone, I have just updated my macOS Monterey and I found something in my Display setting panel which I uploaded below:

It seems that I can set my XV273K with Variable Refresh Rate, just like ProMotion feature?

The XV273K has this in its EDID:

  Vendor-Specific Data Block (AMD), OUI 00-00-1A:
    Version: 1.1
    Minimum Refresh Rate: 48 Hz
    Maximum Refresh Rate: 144 Hz
    Flags 1.x: 0x00

What about displays with Nvidia GSync?

 

[s_muxiu]

The XV273K has this in its EDID:

  Vendor-Specific Data Block (AMD), OUI 00-00-1A:
    Version: 1.1
    Minimum Refresh Rate: 48 Hz
    Maximum Refresh Rate: 144 Hz
    Flags 1.x: 0x00

What about displays with Nvidia GSync?

I didn't find any problem about xv273k with GSync on Windows 10

 

[joevt]

I didn't find any problem about xv273k with GSync on Windows 10

The. Acer XV273K uses AMD FreeSync™ Premium. You are saying it works with Nvidia cards?
My question was about other displays that use GSync instead of FreeSync.

 

[s_muxiu]

The. Acer XV273K uses AMD FreeSync™ Premium. You are saying it works with Nvidia cards?
My question was about other displays that use GSync instead of FreeSync.

Yes I am sure.
the Graphic card of my Game PC is RTX2060s.
I didn't see any GSync issue with my XV273K.

 

[MLM]

I can confirm this was finally fixed.