4K@60Hz 10bit with 15" 2018 MBP?

[ultra20]

Hi,

 

I have a 4K 60Hz monitor which supports 10bit color depth and a 15" 2018 MacBook Pro with a Radeon Pro 560X 4 GB GPU. However, I always get 4K@60Hz 8bit or 4K@30Hz 10bit on my monitor. I have tried various cables like USB-C to HDMI 2.0, USB-C to DP 1.4, USB-C to USB-C (20Gbps with DP ALT support). Does anyone know if this is normal (or does anyone have a suggestion to solve the issue)?

 

Thanks!

[TheKDub]

Do the specific adapters that you have specifically support 4k60hz 10-bit?

 

The 2018 MBP supports 

• Up to two displays with 5120-by-2880 resolution at 60Hz at over a billion colors
• Up to four displays with 4096-by-2304 resolution at 60Hz at over a billion colors

Thunderbolt 3 digital video output

• Native DisplayPort output over USB‑C
• VGA, HDMI, DVI, and Thunderbolt 2 output supported using adapters (sold separately)

"at over a billion colors" would be 10-bit.

• 8 bits per color channel: 16,777,216 total colors
• 10 bits per color channel: 1,073,741,824 total colors
• 12 bits per color channel: 73,876,521,536 total colors
• 14 bits per color channel: 4,398,046,511,104 total colors
• 16 bits per color channel: 281,474,976,710,656 total colors

[ultra20]

Thanks for the quick reply!

• The USB-C to USB-C cable doesn't mention 10bit (it's this one https://www.startech.com/Cables/thunderbolt-3-cables/thunderbolt-3-20gbps-usb-c-cable~TBLT3MM2M)
• The USB-C to DP 1.4 cable supports up to 8K@60Hz bidirectional HDR! (https://www.club-3d.com/en/detail/2470/usb_type_c_cable_to_dp_1.4_8k60hz_m-m_1.8m-5.9ft/)
• I don't have the USB-C to HDMI 2.0 adapter anymore but it supported 4K@60Hz HDR10 (I think it was the following one but it seems like they already don't make them anymore https://www.bol.com/nl/p/deltaco-usbc-hdmi5-usb-c-naar-hdmi-2-0-adapter-met-hdr-10-ondersteuning-ultrahd-4k-60hz-hdcp-2-2-wit/9200000097694751/?productId=9200000097694751&language=en) 

I'm quite sure that HDR support implies 10bit support.

[TheKDub]

1 hour ago, ultra20 said:

Thanks for the quick reply!

• The USB-C to USB-C cable doesn't mention 10bit (it's this one https://www.startech.com/Cables/thunderbolt-3-cables/thunderbolt-3-20gbps-usb-c-cable~TBLT3MM2M)
• The USB-C to DP 1.4 cable supports up to 8K@60Hz bidirectional HDR! (https://www.club-3d.com/en/detail/2470/usb_type_c_cable_to_dp_1.4_8k60hz_m-m_1.8m-5.9ft/)
• I don't have the USB-C to HDMI 2.0 adapter anymore but it supported 4K@60Hz HDR10 (I think it was the following one but it seems like they already don't make them anymore https://www.bol.com/nl/p/deltaco-usbc-hdmi5-usb-c-naar-hdmi-2-0-adapter-met-hdr-10-ondersteuning-ultrahd-4k-60hz-hdcp-2-2-wit/9200000097694751/?productId=9200000097694751&language=en) 

I'm quite sure that HDR support implies 10bit support.

 

Well, that USB C -> HDMI one looks like it's actually doing DisplayPort 1.2 based on the description, which only supports 3840x2400 at 60hz, and doesn't support HDR10 (10-bit)

You need something that supports DisplayPort 1.4 for HDR. HDMI 2.0 also supports HDR10.

 

The USB-C to DP 1.4 cable does support 4K60Hz HDR, so it should be working.

 

And the USB-C to USB-C one only does DP 1.2, so it won't work for 4K60Hz HDR.

 

 

What monitor do you have?

 

https://apple.stackexchange.com/questions/339812/2018-macbook-pro-lg-4k-display-no-60hz Try what they did on there, that *might* fix it.

[ultra20]

I have an Acer PE320QK. Unfortunately, it only supports DP 1.2 according to TFT Central. So in combination with your information, I'm thinking that the MBP is actually always outputting a 10bit signal at 60Hz but the monitor never receives it. In that case it seems like the only way to get the maximum quality out of my monitor is by using the HDMI 2.0 port?

 

On 1/24/2020 at 9:46 AM, TheKDub said:

Well, that USB C -> HDMI one looks like it's actually doing DisplayPort 1.2 based on the description, which only supports 3840x2400 at 60hz, and doesn't support HDR10 (10-bit)

 

On the box it said 4K 60Hz and HDR! But maybe not in combination with each other then? Like I said before, it seems like they already don't make them anymore, so maybe the manufacturer discontinued the product because the quality was not as good as advertised.

[TheKDub]

2 hours ago, ultra20 said:

I have an Acer PE320QK. Unfortunately, it only supports DP 1.2 according to TFT Central. So in combination with your information, I'm thinking that the MBP is actually always outputting a 10bit signal at 60Hz but the monitor never receives it.

Not quite. The macbook would see what the monitor is capable of via that connection and then display whatever options are compatible with it.

 

2 hours ago, ultra20 said:

In that case it seems like the only way to get the maximum quality out of my monitor is by using the HDMI 2.0 port?

Most likely, yes.

 

 

 

By the sound of it, it's not a huge difference between having "HDR" (not actual HDR) enabled or disabled on this monitor. Probably the biggest difference you'd see is sometimes smoother gradients.

[ultra20]

10 hours ago, TheKDub said:

By the sound of it, it's not a huge difference between having "HDR" (not actual HDR) enabled or disabled on this monitor. Probably the biggest difference you'd see is sometimes smoother gradients.

I agree, that's why I only care about 10bit. So I can still use every SDR preset but just with more colors which indeed will also lead to smoother gradients!

 

10 hours ago, TheKDub said:

Not quite. The macbook would see what the monitor is capable of via that connection and then display whatever options are compatible with it

I'd think the same, but I noticed that my MBP says it outputs 30-bit color (ARGB101010) which is also known as 10bit if I'm not mistaken. Here is a screenshot of that information on my MBP (partly in Dutch).

[TheKDub]

3 hours ago, ultra20 said:

I agree, that's why I only care about 10bit. So I can still use every SDR preset but just with more colors which indeed will also lead to smoother gradients!

 

I'd think the same, but I noticed that my MBP says it outputs 30-bit color (ARGB101010) which is also known as 10bit if I'm not mistaken. Here is a screenshot of that information on my MBP (partly in Dutch).

Interesting. Maybe it's already doing 10-bit then, just not "HDR"?

[ultra20]

Yes, that's why I wrote that I think the MBP is actually always outputting a 10bit signal at 60Hz but the monitor never received it (due to DP 1.2). Otherwise, the ARGB101010 in my system report would be false/a bug which is very unlikely.

[ultra20]

After some further research I think that DP1.2 and HDMI 2.0 just don't provide sufficient bandwidth for 4K@60Hz 10bit 4:4:4. That's why MacOS switches the color depth when you change from 30Hz to 60Hz.

[circeseye]

10 hours ago, ultra20 said:

After some further research I think that DP1.2 and HDMI 2.0 just don't provide sufficient bandwidth for 4K@60Hz 10bit 4:4:4. That's why MacOS switches the color depth when you change from 30Hz to 60Hz.

hdmi 2.0 will not do 4k with or without hdr 10bit 444 60hz. not enough bandwith
4k hdr 8bit 444 60hz, or 4k hdr 422 10bit 60hz, or 4k hdr 10bit 444 30hz.

need dp 1.2 or hdmi 2.1 if you go from dp to hdmi 2.0 or vice versa your limited to the hdmi 2.0 spec

 

 

[ultra20]

5 hours ago, circeseye said:

need dp 1.2 or hdmi 2.1 if you go from dp to hdmi 2.0 or vice versa your limited to the hdmi 2.0 spec

 

No, I also tried two cables without a HDMI connection:

• USB-C (DP Alt support) to DP 1.2
• USB-C (DP Alt support) to USB-C (DP Alt support)

That's why I think that the bandwidth of DP 1.2 (and USB-C also) won't be sufficient as well.

[circeseye]

1 hour ago, ultra20 said:

 

No, I also tried two cables without a HDMI connection:

• USB-C (DP Alt support) to DP 1.2
• USB-C (DP Alt support) to USB-C (DP Alt support)

That's why I think that the bandwidth of DP 1.2 (and USB-C also) won't be sufficient as well.

dp 1.2 can do 4k hdr 444 10bit 60hz...but if im reading the specs right usb-c cant, its limited like hdmi 2.0

[ultra20]

Interesting! So maybe it will still be possible if I find a Thunderbolt 3 to DP 1.2 adapter?

[circeseye]

20 hours ago, ultra20 said:

Interesting! So maybe it will still be possible if I find a Thunderbolt 3 to DP 1.2 adapter?

reading on it yes....but it HAS to be thunderbolt to dp. and looking, damn those arnt cheap

[ultra20]

13 minutes ago, circeseye said:

reading on it yes....but it HAS to be thunderbolt to dp. and looking, damn those arnt cheap

The ones I found were also really expensive indeed! And I think they were also always Thunderbolt 3 to 2x DP 1.2 which I don't need.

I was also thinking about trying a thunderbolt 3 to thunderbolt 3 cable (40 Gbps) which supports DP Alt mode. But I wouldn't be surprised if DP Alt actually just uses up to 20 Gbps (so it becomes a USB-C cable).