P2615Q, Surface Book 2, HDR 8-Bit + FRC support

Question

Marhaba folks! Hope y'all doing great!

I've been scouring the internet for a day to check if Surface Book 2 can provide 4K@60Hz HDR output to my Dell P2715Q monitor. The closest I could get is this discussion suggesting HDMI 2.0b cable. But the P2715Q only supports HDMI 1.4 and DisplayPort 1.2. Looking for advice on whether this would work before I buy the cable?

Can my current DP cable support 4K@60Hz HDR output? I have the P2715Q running at 4K@60Hz and even two at 4K@30Hz with MST but no HDR. I know the integrated Intel cpu can provide HDR because the Surface Book 2 integrated display is easily picked up as such.

Following are the specs for surface book 2:
CPU: Intel Core i7-8650U
Display Driver: Intel UHD Graphics 620 version 27.20.100.8682
OS: Windows 10 Pro 20H2 build 19042.1288

My intuition about 8-Bit + FRC displays is that graphics card pushes out 10-bit color signal but it gets simulated on the monitor's end. Ideally, I would like 2x4K@60Hz HDR. But I don't think USB Type-C Gen 1 can push out that much bandwidth. So I'm ok with single 4K@60Hz HDR for now as docks are kinda expensive. Just need best cable recommendations. Any help is very much appreciated!

Cheers!

jphughan · Accepted Answer

@oheisme Happy to help. Sorry I didn't have better news though! In terms of the display though, I haven't delved into its specs, but I know that some displays derive display 10-bit color but derive it from an 8-bit signal, as opposed to being able to receive a true 10-bit signal. This is similar to displays that support 120 Hz refresh rates and frame interpolation but still only support receiving a 60 fps signal. The additional frames are derived, not actually received from the source. So if that's all the display can do, then you're not missing out. If the display CAN receive a true 10-bit signal, then I'm not sure that's available from that Intel GPU. For a while, even in the discrete GPU space of AMD/NVIDIA, that capability was reserved for the pro GPUs (FirePro/Quadro) and was locked out on their consumer GPUs (Radeon/GeForce).

And again, even that wouldn't get you full HDR. If you want a true HDR experience, you'll want a true HDR display and a system that can send it an HDR signal. And since maximum brightness can significantly affect the quality of the HDR experience (for effects like bright flashes of light, etc.) VESA has developed the DisplayHDR rating system that you might want to check for when shopping around, because achieving high brightness has historically been a challenge, especially on laptop displays, so not all HDR is created equal. Lastly, also be aware that Windows in general still offers a pretty rocky HDR experience, simply because so few applications and content are optimized for HDR, and Windows doesn't do a great job of faithfully rendering SDR content when operating in HDR mode. It's gotten better over the years, but it still isn't great, with colors on SDR content just looking "off". And that assumes that even the actual HDR content actually works properly when it should, which it doesn't always. I remember Chrome being a particular sticking point with Windows HDR, but that may have been resolved by now.

jphughan · Answer

@oheisme First, it's worth noting that HDR in common usage is not the same as 10-bit color. HDR typically refers to either HDR10, HLG, or Dolby Vision. Those weren't added to DisplayPort until v1.4. DisplayPort 1.2 and even HDMI 2.0 can only achieve 4K 60 Hz with HDR by running reduced chroma, such as 4:2:2 or 4:2:0. PCs typically use full chroma (4:4:4), and I'm not sure you can configure them to use chroma subsampling. Whether the display would accept that signal especially over DP is another question as well.

The GPU in the Surface Book 2 only supports DisplayPort 1.2 via external outputs. Intel GPUs didn't gain DP 1.4 until the ones built into the SOME Core 10th Gen CPUs -- namely those that use the "Ice Lake" architecture -- and then Core 11th Gen CPUs. The built-in display can run HDR because the internal connection uses eDP, i.e. embedded DisplayPort, and it supports eDP 1.4.

And even if the GPU weren't an issue, the P2715Q is a 2015 model year display, so it predates both DP 1.4 and HDMI 2.0. And to my knowledge it doesn't support any formal HDR standards.

jphughan · Answer

@oheisme  One additional note to expand on the HDR vs. 10-bit color distinction.  HDR stands for 'High Dynamic Range', which actually refers to a wide range of luminosity (brightness), not a wide range of colors.  Basic 10-bit color is typically called WCG (wide color gamut).  That does not include any expansion of luminosity range.  The formal HDR10 standard includes support for WCG and also a wide range of luminosity, but not all WCG implementations support HDR.

oheisme · Answer

@jphughan wrote:

In terms of the display though, I haven't delved into its specs, but I know that some displays derive display 10-bit color but derive it from an 8-bit signal, as opposed to being able to receive a true 10-bit signal. This is similar to displays that support 120 Hz refresh rates and frame interpolation but still only support receiving a 60 fps signal. The additional frames are derived, not actually received from the source.

That would certainly clear my doubt about how this monitor was capable of 1073741824 colors (using 8bit + frc) with only display port 1.2 and hdmi 1.4 ports. It makes sense windows recognizes this monitor that 8bit display also. But the colors are still pretty decent overall, so I'm happy with it

The Vesa DisplayHDR rating seems very useful for future purchases. Thanks again for all the info again!

Cheers and take care!

oheisme · Answer

@jphughan Thank you! Thats a lot of helpful information about HDR and intel gpu support. So my hopes of making it work with Surface Book 2 are probably out the door. But, given the monitor is marketed to support 8bit + frc (even checked with dell support to confirm that internal tool specify the monitor supports hdr using software simulation), is their a scenario (using desktop gpu, or thunderbolt 3 compatible laptop) I can make this monitor display somewhat of an illusion of 10bit color space, using flicker technology explained here. I know I'm getting into the general recommendation category but just curious about hdr display on these monitors because some hdr videos look phenomenonal on my surface book display.

Thanks

oheisme · Answer

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Monitors

P2615Q, Surface Book 2, HDR 8-Bit + FRC support

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