madshi bug tracker - madVR
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0000620madVRbugpublic2019-09-30 05:192019-10-01 17:38
OmbraRD 
madshi 
normalminoralways
closedno change required 
PCWindows10 1908
0.92.17
MPC-HC 1.8.7
LAV Splitter 0.74.1.22-git
LAV Video Decoder 0.74.1.22-git
DXVA2 Copyback
auto mode
yes
On
fullscreen exclusive mode
NVidia
GTX 1080
436.30
0000620: Dithering options have no effect when full screen on a 4K HDR display
When you try to play a 4K HDR 10bit x265 movie on a 4K HDR compatible display as long as you are full screen, dithering options have no effect.
1. Open a 2160p x265 file that is 10bit HDR in Media Player Classic with madVR enabled.
2. Search for a scene where you can easily spot banding (normally dark scenes like in the beginning of Creed II)
3. Check the dithering in window mode.
4. Check the dithering in full screen mode.
No tags attached.
jpg Dither.jpg (5,127,467) 2019-10-01 16:44
http://bugs.madshi.net/file_download.php?file_id=317&type=bug
Issue History
2019-09-30 05:19OmbraRDNew Issue
2019-09-30 09:35madshiNote Added: 0002557
2019-10-01 02:14OmbraRDNote Added: 0002560
2019-10-01 08:17huhnNote Added: 0002561
2019-10-01 16:44OmbraRDFile Added: Dither.jpg
2019-10-01 16:47OmbraRDNote Added: 0002562
2019-10-01 16:52madshiNote Added: 0002563
2019-10-01 17:08OmbraRDNote Added: 0002564
2019-10-01 17:19madshiNote Added: 0002565
2019-10-01 17:22OmbraRDNote Added: 0002566
2019-10-01 17:25madshiNote Added: 0002567
2019-10-01 17:35OmbraRDNote Added: 0002568
2019-10-01 17:38madshiStatusnew => closed
2019-10-01 17:38madshiAssigned To => madshi
2019-10-01 17:38madshiResolutionopen => no change required

Notes
(0002557)
madshi   
2019-09-30 09:35   
Does it help if you manually switch your "device\your display\properties" settings to 8bit instead of "auto" or 10bit?
(0002560)
OmbraRD   
2019-10-01 02:14   
I have exclusive full screen mode enabled but even without it when i go full screen MPC reports (Ctrl+J) 10 bit mode but as soon as i switch to window mode it goes to 8 bit and the dithering works fine.
(0002561)
huhn   
2019-10-01 08:17   
that's working as intended windows 10 supports windowed fullscreen 10 bit.

if you switch madVR to 8 bit it will not try to use 10 bit anymore.
(0002562)
OmbraRD   
2019-10-01 16:47   
I get the same result in exclusive or windowed fullscreen. In both i get no dithering. Only in window mode (not fullscreen) because it switches to 8 bit.

I attached a photo to hopefully show better what i mean.
(0002563)
madshi   
2019-10-01 16:52   
If you want support, it would help if you actually answered my questions... ;-)

I'm still waiting for a clear answer to the question I asked in my first post.
(0002564)
OmbraRD   
2019-10-01 17:08   
Sorry madshi, you are totally right!

Just tested switching to 8bit and dither works correctly
(0002565)
madshi   
2019-10-01 17:19   
That means that your display probably doesn't handle 10bit input correctly. Or alternatively it's also possible that either the OS or the Nvidia driver are screwing something up with 10bit output. In any case, don't worry about it, using 8bit output is perfectly fine.
(0002566)
OmbraRD   
2019-10-01 17:22   
I understand. Display should support if fine. It is an LG OLED B7 but while investigating the gfx side i found this:

https://hub.displaycal.net/forums/topic/how-to-enable-dithering-on-nvidia-geforce-with-windows-os/ [^]

I tried a bunch of options but it won't enable.

I guess i'll run it in forced 8bit then. Thank you!
(0002567)
madshi   
2019-10-01 17:25   
We do not want the GPU driver to add dithering. If we need dithering, madVR will do that in higher quality. But if you output 10bit, madVR will automatically lower the amount of dithering, because 10bit needs 4 times less dither noise than 8bit. So it will *look* to you as if dithering is not working. But madVR actually will properly dither the output, in any case. But if someone (display, GPU, OS) breaks the 10bit chain, that will effectively remove madVR's dithering.

Short summary: It's not the dithering you need to worry about. It's the proper handling of 10bit. Which seems to be broken in your playback chain, for whatever reason.

In any case, don't worry about it, just use 8bit output instead. Problem solved.
(0002568)
OmbraRD   
2019-10-01 17:35   
Alright, thanks