Having trouble getting 0-255 from nVidia HDMI out - AVS Forum
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post #1 of 9 Old 09-16-2014, 10:36 AM - Thread Starter
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Question (Solved) Having trouble getting 0-255 from nVidia HDMI out

For some reason, I can' t get full RGB from my nVidia HDMI out. My setup is mpc-hc+madvr+lav -> AVR -> TV. I took out AVR from the equation to see if that is the culprit, but no.

TV:
Samsung HU8550.
Mode: movie (tried standard, same problem)
HDMI black level is set to Normal.
Using HDMI 4 (ARC input). Same problem if I use HDMI 2 DVI input even if it is re-named to PC DVI.

nVidia:
HDMI audio is enabled.
custom resolution: UHD@23.976Hz
Output mode: RGB (tried YCbCr:444, same problem)
Dynamic range: let video player decide (also tried let nVidia decide and chose Full RGB, same problem)

madVR: TV output range: 0-255.

When I play a test pattern on mpc-hc, it is not showing me the full range, and my blacks and whites are getting clipped.
Now here's the interesting thing, if I change madVR output to 16-235 instead, then I am getting a washed out blacks, BUT, the test pattern looks correct and shows all the color ranges. I can't understand how to explain this. So I decrease TV's brightness and get reasonable image from mpc-hc, but then this makes everything else (desktop, xbmc, other players) too dark.

I've tried various methods that people say to get 0-255:
1) Create a custom rez (I already have this).
2) Run number of registry fix tools that claim to fix nVidia HDMI RGB range problem

but can't seem to fix the output range issue. Any ideas, suggestions? Also can someone explain how setting madVR output to limited range gives me the full spectrum?

Last edited by bcec; 09-16-2014 at 10:39 PM.
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post #2 of 9 Old 09-16-2014, 01:57 PM
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Originally Posted by bcec View Post
When I play a test pattern on mpc-hc, it is not showing me the full range, and my blacks and whites are getting clipped.
It would be helpful to be more specific. For example, if you are talking about AVS HD 709 Black Clipping, you would give the numbers for the visible bars, and describe the effect of adjusting Brightness on the bars.

That said, if you are expanding Video Levels to PC Levels, you will never see the bars below 17 and above 234, because 0-16 have been replaced with 0, and 235-255 with 255, with the remaining 17-234 unevenly expanded into 1-254.

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Originally Posted by bcec View Post
HDMI black level is set to Normal.
I don't know anything about Samsungs, but "Normal" usually is Video Levels, because that's the standard for video. If you are outputting PC Levels to a TV set up for Video Levels, you will have black and white crush. See this post for much more on levels:

AVS HD 709 - Blu-ray & MP4 Calibration
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post #3 of 9 Old 09-16-2014, 02:09 PM - Thread Starter
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Thanks for the response.

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Originally Posted by sawfish View Post
It would be helpful to be more specific. For example, if you are talking about AVS HD 709 Black Clipping, you would give the numbers for the visible bars, and describe the effect of adjusting Brightness on the bars.
I am using Spears & Munsil, and one of the patterns they have contains black bars labeled -4% -2% 2% and 4%. I am not seeing -4 & -2% bars at all (even when I crank up the brightness of the TV), which tells me that 0-15 is clipped to become 16. Similar for whites using other test patterns.

What's interesting is when I switch madVR output from 0-255 to 16-235, then I start seeing -4% & -2%. This is complete opposite of what I would expect. Unfortunately, when I use 16-235 (so that BTB/WTW information is retained), image is looking washed out, which makes me bring down the brightness a lot. That is fine for video played through madVR, but that makes everything else quite dark (including other video players like powerDVD).

Quote:
I don't know anything about Samsungs, but "Normal" usually is Video Levels, because that's the standard for video. If you are outputting PC Levels to a TV set up for Video Levels, you will have black and white crush. See this post for much more on levels:

AVS HD 709 - Blu-ray & MP4 Calibration
Samsung's HDMI Level=Normal corresponds to RGB 0-255. The other value is "Low", which corresponds to 16-235

Last edited by bcec; 09-16-2014 at 02:12 PM.
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post #4 of 9 Old 09-16-2014, 02:30 PM
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Originally Posted by bcec View Post
Thanks for the response.

I am using Spears & Munsil, and one of the patterns they have contains black bars labeled -4% -2% 2% and 4%. I am not seeing -4 & -2% bars at all (even when I crank up the brightness of the TV), which tells me that 0-15 is clipped to become 16. Similar for whites using other test patterns.
Not quite. As you are outputting PC Levels, 0-16 are being replaced with 0, and the negative percentages are in this range. AVS HD 709 is easier to talk about, because the bars are labeled with the actual pixel values they are encoded with. In any case, what you described is expected when outputting PC Levels.

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Originally Posted by bcec View Post
What's interesting is when I switch madVR output from 0-255 to 16-235, then I start seeing -4% & -2%. This is complete opposite of what I would expect. Unfortunately, when I use 16-235 (so that BTB/WTW information is retained), image is looking washed out, which makes me bring down the brightness a lot. That is fine for video played through madVR, but that makes everything else quite dark (including other video players like powerDVD).
Again, expected. The post I linked to explains all this.

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Samsung's HDMI Level=Normal corresponds to RGB 0-255.
Well, that's Samsung for you. Switching MadVR to Video Levels creates a level mismatch which I described in the post I linked to; as I said, "When the TV is at PC Levels and the video device is Video Levels, the picture will look gray and washed out; on AVS HD 709, you will see Bars < 17 flash."
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post #5 of 9 Old 09-16-2014, 03:31 PM - Thread Starter
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I thought that I need to have TV & PC set to 0-255, and that would give me the full range, including information for <16 and >236. What you are saying is that if I have them both set to 0-255, I will never get <16 & >235. Did I understand it correctly? This is counter intuitive. I don't understand why setting full range for both PC and TV would loose portion of the data.

Regardless, the issue is I am getting limited range from PC and TV is set to full range. I am trying to get PC to output full range as well, but with no success so far.
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post #6 of 9 Old 09-16-2014, 04:22 PM
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Quote:
Originally Posted by bcec View Post
I thought that I need to have TV & PC set to 0-255, and that would give me the full range, including information for <16 and >236. What you are saying is that if I have them both set to 0-255, I will never get <16 & >235. Did I understand it correctly? This is counter intuitive. I don't understand why setting full range for both PC and TV would loose portion of the data.
Because that's what happens when Video Levels ("Limited Range") are expanded to PC Levels ("Full Range"). The full/limited terminology should be abolished because it's too confusing, as the real difference is the reference black and white points, and outputting video as "full range" means expanding [16-235] to [0-255] and throwing away BTB and WTW. Read the message I linked to a few times and give it a chance to sink in. "Full range" means discarding information and scaling values unevenly as opposed to "Limited Range", which is passthrough. That is, if your video player is outputting Video Levels, the video card doesn't need to touch the video in any way. As long as your TV is configured for Video Levels, it should calibrate the same as when using a BD player or other video device as source. Complications arise because some people want video and desktop to be consistent, so one collection of TV settings works perfectly for both, which means expanding Video Levels to PC Levels when playing video, and when cards do stupid things like compressing the desktop to Video Levels.

To be clear, this levels expansion I've been talking about applies to playing video. It should not be happening when viewing the desktop, photos, games, etc. Video players can use Video Levels (passthrough) or PC Levels (expansion).

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Regardless, the issue is I am getting limited range from PC and TV is set to full range. I am trying to get PC to output full range as well, but with no success so far.
I believe what you described originally is correct behavior, when you had MadVR and the TV configured for PC Levels. Everything you described is expected and how it's supposed to work. The custom resolution and registry hack may not even have done anything. They've never been necessary for my Sony LCDs and Panasonic plasma hooked up with HDMI, and apparently their usefulness depends on the display. Once you understand levels, I described in this recent message how I was finally able to force my Nvidia GT430 to compress the desktop to Video Levels, which is the problem some people say affects them inherently and fix with the aforementioned hacks:

AVS HD 709 - Blu-ray & MP4 Calibration

At the end of this message, I described the several advantages (and one negligible disadvantage) I find in outputting video at the standard Video Levels for my HTPC instead of expanding to PC Levels as recommended by MadVR users, but then I don't use MadVR, just WMC and XBMC:

AVS HD 709 - Blu-ray & MP4 Calibration
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post #7 of 9 Old 09-16-2014, 05:09 PM - Thread Starter
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Ah-ha, thanks for all these long explanations. I think I am starting to get the hang of it.

1) This is one of the test images from Spears&Munsil. It should look like this (almost all white blocks are visible, a thin white stripe at the center, small darker square inside colored squares):


2) With my current setup, it looks like this (white blocks are mostly gone, a thick stripe at the center, colored squares have no small dark square in them):


3) When I switch madVR output from 0-255 to 16-235, I get this (whites and blacks are greyish):


So I am starting to understand what you are saying, that my levels are already correctly setup, and both pc and tv are set to 0-255, which results in image #2 . Calibration wise it is correct, but I loose the extra information in the video signal, but gain similar colors for desktop and videos.

If I want the best quality video and retain BTB/WTW information, I need to keep nVidia at 0-255, switch madVR to 16-235, and switch TV to 16-235. This should keep give me 1), but desktop color will be crushed.

I assume madVR output and TV settings should always match, right? So I can also try:
nVidia 16-235, madVR 0-255, TV 0-255
nVidia 16-235, madVR 16-235, TV 16-235. <- I suspect this could give me similar desktop & video colors, and I won't lose BTB/WTW. Any disadvantages for doing this?

Last edited by bcec; 09-16-2014 at 05:14 PM.
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post #8 of 9 Old 09-16-2014, 07:14 PM
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Originally Posted by bcec View Post
Ah-ha, thanks for all these long explanations. I think I am starting to get the hang of it.
I'm just happy to hear someone didn't find them tl;dr.

Quote:
Originally Posted by bcec View Post
So I am starting to understand what you are saying, that my levels are already correctly setup, and both pc and tv are set to 0-255, which results in image #2 . Calibration wise it is correct, but I loose the extra information in the video signal, but gain similar colors for desktop and videos.
Yes!

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Originally Posted by bcec View Post
If I want the best quality video and retain BTB/WTW information, I need to keep nVidia at 0-255, switch madVR to 16-235, and switch TV to 16-235. This should keep give me 1), but desktop color will be crushed.
Yes! For my HTPC, I see image (1). It's set up as I described at the end of this message, and you're right about the desktop inconsistency, which I explained doesn't matter in the slightest bit for my purposes:

AVS HD 709 - Blu-ray & MP4 Calibration

The idea is for the PC to output the video unaltered, without any messing around with levels.

Quote:
Originally Posted by bcec View Post
I assume madVR output and TV settings should always match, right? So I can also try:
1. nVidia 16-235, madVR 0-255, TV 0-255
2. nVidia 16-235, madVR 16-235, TV 16-235. <- I suspect this could give me similar desktop & video colors, and I won't lose BTB/WTW. Any disadvantages for doing this?
I don't think that's going to help. If you want desktop and video consistency, you should go with PC Levels.

If by "Nvidia 16-235" you mean compressing all output to 16-235 as I found is possible by setting the pixel format to YCbCr444, I wouldn't do that unless the TV only supported 16-235. If instead you meant fooling with the Nvidia Control Panel's Video Dynamic Range option, I wouldn't touch that entire section for the reason I gave here:

http://forum.xbmc.org/showthread.php?tid=180884

If it's the first thing, compressing 0-255 (all output) to 16-235, then the TV needs to be set to Video Levels (16-235), and video needs to be expanded to PC Levels so it too can be appropriately compressed. That's a "levels round trip", and you want to avoid doing it. I described how I was able to force it to happen here:

AVS HD 709 - Blu-ray & MP4 Calibration

I know madVR users warn about banding showing up in gradients when there's a round trip. I believe I've also read about them getting into trouble with double compression or expansion. There are lots of variables, and don't forget the player software.
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post #9 of 9 Old 09-16-2014, 10:38 PM - Thread Starter
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Thank a lot for all the help and explanations Alright, I set nvidia/windows to 0-255, and madvr+TV to 16-235, used AVS HD 709 to recalibrate and all looks great! Also set limited range on Xbmc, so that looks good too.

The only thing left to fix is Stereoscopic Player, but I couldn't find a place to change its output levels to 16-235. Worst case, I will switch TV to 0-255 when watching 3D content.
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