I think your Windows desktop setting is probably 8 bit.
MadVR converts to RGB so having your desktop set to YCbCr there will be a conversion back by your video card.
The best way to watch HDR 4K content from MadVR is to configure it to do dynamic tone-mapping if your GPU can handle it.
Projectors are not HDR devices but if yours has dynamic tone-mapping built in and switched on then it's probably going to be easier and more straight forward to send it HDR.
https://www.cnet.com/news/why-you-shouldnt-expect-great-hdr-from-a-projector/
Yes, my Windows desktop is set to 8 bit RGB. With 4K 60 Hz, 8 bits is the best you can do on HDMI 2.0 .
I tried to force my desktop to do YCbCr420 and 12 bits. In this case, MadVR indeed will send BT.2020 to the projector in 12 bits, and the color looks correct - same as they do from the Sony player. IMO, one shouldn't be required to downgrade the desktop's resolution from RGB to YCbCr420. I'm playing the movie full-screen, and MC has an opportunity to change the video mode, and indeed, does change it from 60 Hz to 24 Hz, and the color space from Rec 709 to BT.2020 . The only thing it doesn't seem to be able to change is the pixel depth and chroma sampling, for some reason.
It should be noted that the Sony player can send 12 bits in YCbCr444 to the projector. There is enough bandwidth on HDMI 2.0 to do that at 24 Hz. I'm unable to find any way to get MediaCenter + MadVR to do the same. The best it can do is YCbCr420 12 bits for 4K/24 Hz.
In fact, my Sony player has custom HDMI settings. I was able to force it to use RGB 12 bits also. It works fine because there is once again enough bandwidth to do RGB 12 bits at 4K / 24 Hz on HDMI 2.0.
Once the move player was sending all 12 bits, I couldn't discern any difference in the movie between YCbCr444 12 or RGB 12 bits from the Sony player. YCbCr420 12 bits from MC25 also looked pretty much the same. That's probably because the Blu-ray discs themselves are encoded in 420 chroma subsampling, so there is no benefit to going higher.
As an experiment, I also forced the Sony player to play the movie at 60fps, by disabling the "24p" playback option. I had also forced RGB in the player. In this case, the Sony player sets the video signal to 4K 60 YcCbCr BT2020. The Marantz receiver is unable to figure out the pixel depth, oddly. The colors look correct, though.
I'm aware that MadVR has tone mapping for HDR to SDR. I have played with it, actually. I find that I personally prefer to have the HDR processed by my UHD65 projector. I have read threads on AVSForum that recommend using the MadVR tone mapping with this projector, in fact. I just haven't found it to be preferable in my environment. I have a fully light controlled room, and a very high gain screen - DA-Lite High Power. Either 2.4 or 2.8 gain. It's a 17-year old 106" screen. Somehow, that screen seems to do wonders with HDR on the UHD65 when using the Sony UHD BD player.
I'm well aware that consumer projectors aren't truly HDR displays. They can't achieve the necessary brightness. However, IMO, it is important for the colors to look correct, and they are just not correct when sending BT.2020 over just 8 bits.
Try as I might, I haven't been able to get my Sony player to misbehave into doing the same. I'm not sure where the fault lies exactly, whether it's Microsoft, nVidia, MC25 or MadVR. But it currently doesn't make for a good user experience.
Microsoft and nVidia probably have a fair bit of responsibility here. If I use run the desktop at 4K 60 Hz, the nVidia drivers defaults to 8 bit RGB. Then, if I enable "Windows HD color", it switches to sending BT.2020 at 8 bits, which is worse than useless, IMO. All it does is get the display to claim it's showing HDR, when it's actually not providing any benefit.
I would welcome some options in MC25 and/or MadVR to set the color depth and chroma subsampling. Ideally, these should go in the "custom modes" tab of MadVR display modes. At the moment, only the width, height and Hz can be customized. It's not possible to select either the bit depth (8, 10, 12 bits) or the chroma subsampling (YCbCr420, 422, 444, RGB). Only the nVidia control panel can do those, but that's for the desktop only. If it was possible to select a combination of all these in MadVR, I think including a bunch of presets that make sense for BD discs, along with some code to avoid ever trying to pack HDR data in 8 bits, so that non-sensical modes don't get selected.
I also just bought a brand new 82" Samsung Q70 TV purchased at Costco over the week-end, which may actually be capable of real HDR. It's still only HDMI 2.0, though, not 2.1. There was an LG HDMI 2.1 in the store that was 86" and about $700 less than the Samsung. Unfortunately, its picture looked far worse from all standpoints. I checked the ratings on some review site, and they confirmed that it was a night and day difference. The LG OLED probably outperformed both, but it was 2.5x the price and not on display.
So, I also have a HTPC hooked up to my Q70. There is no audio receiver involved (yet). It's still on the floor stand in my master bedroom, and hasn't been mounted to the wall. That HTPC is also using an nVidia GPU, a GT.1030 . I can tell that the colors are all wrong when playing UHD BD. I haven't tried downgrading the desktop to YcbCr420 yet. I don't have a separate UHD 4K BD player hooked up to the TV to compare, also. I do have the built-in streaming apps, though. I own the streaming version of the "Last Jedi" disc in 4K also, and can play it through the built-in Amazon Prime Video app on the TV. Colors look gorgeous with proper colors right off the bat in HDR without having to mess with any TV settings. I'd like to think the Blu-ray disc should look a bit sharper due to the 4x higher bit rate. But when the colors are off, it doesn't really matter how sharp the movie looks
.
Anyway, I haven't found anything in the Samsung TV menus that shows enough details about the video mode in terms of color depth and color space. I don't have a Marantz receiver in between the HTPC and the TV to play HDMI analyzer. Is there some debug info about the video mode in MC25 I could use to see what it's actually set to ? I would think nVidia might have some sort of log also, but I haven't found that yet. I would need to be able to look at it while MC25 is playing the movie full-screen.
Author
Topic: UHD 4K Blu-ray disc playing with "8-bit HDR" (Read 4879 times)