Reference Black vs Computer Black - AVS Forum | Home Theater Discussions And Reviews
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post #1 of 45 Old 09-07-2015, 10:57 PM - Thread Starter
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Reference Black vs Computer Black

I'm a bit confused. If I play the AVS black level test pattern in Plex on my TV and adjust black levels so 17+ is flashing (which happens to be Sonys default setting for "Cinema Pro" or 50)... It looks like you would expect...

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If I then quit Plex to my Mac Mini desktop (don't change TV settings at all) and load the test pattern in Preview, it looks like this... The full range is visible...

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What is going on here? I would have expected my desktop to show 1-16 as pitch black.

Without changing anything on the TV, why is 16 black in Plex, but the same test pattern on my Mac desktop indicates 0 is black? Is this right? Can someone make sense of it for me?

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post #2 of 45 Old 09-08-2015, 11:30 AM
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That's the way it works.

Video content has black at 16, PCs use 0 as black.

Depending on how you view the content (video player, jpg viewer, ect..) you'll get different results.
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post #3 of 45 Old 09-08-2015, 11:32 AM - Thread Starter
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Originally Posted by sotti View Post
That's the way it works.

Video content has black at 16, PCs use 0 as black.

Depending on how you view the content (video player, jpg viewer, ect..) you'll get different results.
Thanks... so my TV is set correctly?

Also, I notice that Kodi has a setting for using 16-235... that is currently off and Kodi produces the same result at Plex (first attached image above). What will enabling that setting do? Should I turn it on or leave it off?
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post #4 of 45 Old 09-08-2015, 12:06 PM - Thread Starter
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I came across this great post by member sawfish that may help my situation... but I have a few questions...

Quote:
I agree, but I think it's potentially confusing to say the GPU should output "limited color range". Unless the TV doesn't support it, the GPU should output RGB 0-255, the PC default. As I understand it, the only alternative is for it to compress everything to 16-235, either as RGB or YCbCr. For this to work for video, video must first be expanded to RGB 0-255, causing the dreaded levels round trip of 16-235 to 0-255 to 16-235. I'm going to assume below the card is outputting RGB 0-255, which means it can pass through whatever is presented to it.

As for the video player and TV, the main consideration is, do you want consistency between desktop and video? If so, the video player should expand Video Levels to PC Levels, i.e. 16-235 to 0-255, and the TV should be set to PC Levels ("Non-standard" for my ST60). For video, this discards BTB and WTW and scales all the values in between into 0-255, which is necessary for Black = 0 and White = 255 to work for video as well as the desktop. If you don't care about this, then your video player can leave the video untouched and output Video Levels, and your TV should be set accordingly ("Standard" for my ST60). This is the WMC default and Kodi's "Use limited range" option. This is passthrough for video and preserves BTB and WTW, but the TV will crush black and probably at least some white on the desktop, as it should be calibrated for Black = 16 and White = 235 (overshoots allowed). This is not a problem unless you use the PC for gaming, critical picture viewing, and whatnot. It won't interfere in the least with using WMC or Kodi, nor will it interfere with maintaining the PC and even writing letters and such. This choice provides consistency with video devices like streamers, BD players, etc, some of which may not have RGB 0-255 output options, e.g. my Sony S5100 BD player only has RGB 16-235 (however, unlike a PC, it doesn't appear to do a levels round trip). This consistency would let you hook everything up to an AVR and use a single AVR HDMI output.

Agree completely with using the TV for all calibration. I use the second of the two approaches just above, and my PC and BD player measure the same under the same calibration, which is all done with the TV. This was not the case when I had the video player output PC Levels; then, I had to make some tweaks to Brightness in the Nvidia Control Panel to get Bar 17 to show up in AVS HD 709 Black Clipping.
Can someone confirm or correct my understanding?

- My Mac is outputting 0-255 full range on the desktop?
- Video playback in Kodi/Plex has limited output from 16-235?
- My current TV black level is correct (black at 16 for video and 0 on the computer desktop)?

Now what I don't understand is what Kodi's "use limited range" does? It already seems to output a limited range... even without enabling this option? What am I missing? It sounds like Kodi's "use limited range" does the opposite and passes through full 0-255? I'm very confused about this.
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post #5 of 45 Old 09-08-2015, 01:52 PM
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Quote:
Originally Posted by virtualrain View Post
I came across this great post by member sawfish that may help my situation... but I have a few questions...

Can someone confirm or correct my understanding?

- My Mac is outputting 0-255 full range on the desktop?
- Video playback in Kodi/Plex has limited output from 16-235?
- My current TV black level is correct (black at 16 for video and 0 on the computer desktop)?
Going by your first post, your video card is outputting 0-255, Kodi/Plex are expanding video from 16-235 to 0-255, and your TV is set for 0-255. Unlike Kodi/Plex, your paint program is just displaying the image without any alteration. This is all fine if you want the desktop/video consistency I talked about in the message you quoted. You can verify by playing Black Clipping in Kodi/Plex, then raising Brightness on the TV and failing to see bars below 17 light up. They won't, because that information was lost in the 16-235 to 0-255 expansion.

Quote:
Now what I don't understand is what Kodi's "use limited range" does? It already seems to output a limited range... even without enabling this option? What am I missing? It sounds like Kodi's "use limited range" does the opposite and passes through full 0-255? I'm very confused about this.
Kodi's "Limited Range" option is the passthrough for video I talked about in that message. It doesn't touch video, but unlike WMC, it does alter its UI so that the UI won't be crushed, not that it really matters that much.
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post #6 of 45 Old 09-08-2015, 02:00 PM - Thread Starter
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Quote:
Originally Posted by sawfish View Post
Going by your first post, your video card is outputting 0-255, Kodi/Plex are expanding video from 16-235 to 0-255, and your TV is set for 0-255. Unlike Kodi/Plex, your paint program is just displaying the image without any alteration. This is all fine if you want the desktop/video consistency I talked about in the message you quoted. You can verify by playing Black Clipping in Kodi/Plex, then raising Brightness on the TV and failing to see bars below 17 light up. They won't, because that information was lost in the 16-235 to 0-255 expansion.
Ok thanks, this makes sense. I was a bit confused that raising black level while playing the pattern didn't reveal more bars on the test pattern... I thought they were left off. Now I see they were clipped off.

Is there anything I can do to preserve the WTW? I'm not sure I should care about BTB... right?

Quote:
Originally Posted by sawfish View Post
Kodi's "Limited Range" option is the passthrough for video I talked about in that message. It doesn't touch video, but unlike WMC, it does alter its UI so that the UI won't be crushed, not that it really matters that much.
Sorry, but do you recommend using this option or not? Will this preserve the WTW? Would I need to re-adjust my black levels?
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post #7 of 45 Old 09-08-2015, 03:36 PM
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Originally Posted by virtualrain View Post
Is there anything I can do to preserve the WTW?
No.

Quote:
I'm not sure I should care about BTB... right?
It does help one set Brightness.

Quote:
Sorry, but do you recommend using this option or not?
See my post that you quoted. I can't really "recommend" anything so instead I described the trade-offs. As I said, I personally use the passthrough approach, because the calibration is better, and I don't care about desktop/video consistency or the desktop being crushed, because it doesn't matter for my usage of WMC and Kodi.

Quote:
Will this preserve the WTW? Would I need to re-adjust my black levels?
The passthrough approach should preserve both WTW and BTB. You would need to set your TV to "Standard" or whatever it calls Video Levels, and then check all the settings.
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post #8 of 45 Old 09-08-2015, 03:43 PM - Thread Starter
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Quote:
Originally Posted by sawfish View Post
No.

It does help one set Brightness.

See my post that you quoted. I can't really "recommend" anything so instead I described the trade-offs. As I said, I personally use the passthrough approach, because the calibration is better, and I don't care about desktop/video consistency or the desktop being crushed, because it doesn't matter for my usage of WMC and Kodi.

The passthrough approach should preserve both WTW and BTB. You would need to set your TV to "Standard" or whatever it calls Video Levels, and then check all the settings.
Thank you very much, I'll try some things this evening. I don't care about desktop crush as my Mac is exclusive to Plex/Kodi (I'm still trying to figure out which player is better).

My TV has the following settings...

Quote:
The HDMI® Dynamic Range feature helps produce natural color by changing the luminance tone reproduction of HDMI input color signals. The dynamic range of the image is reproduced properly by selecting the desired dynamic range for signal type being used.
Use the Auto setting during normal operation. The Auto setting automatically selects the dynamic range Full or Limited based on dynamic range information coming from connected device.
The Full setting should be used when you would like the signal range fixed to full range. An example may be a high-definition signal from a device connected using an HDMI cable.
Limited: The signal range is fixed to limited range. This should be used when less color is desired.
If I want to go the passthrough route to preserver WTW and BTB, should I be using Full or Limited?

EDIT: Never mind... I found this, which explains the TV settings more clearly...

http://forum.kodi.tv/showthread.php?...501#pid1995501

Last edited by virtualrain; 09-08-2015 at 04:29 PM.
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post #9 of 45 Old 09-08-2015, 04:45 PM
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Quote:
Originally Posted by sawfish View Post
It does help one set Brightness.

See my post that you quoted. I can't really "recommend" anything so instead I described the trade-offs. As I said, I personally use the passthrough approach, because the calibration is better, and I don't care about desktop/video consistency or the desktop being crushed, because it doesn't matter for my usage of WMC and Kodi.

The passthrough approach should preserve both WTW and BTB. You would need to set your TV to "Standard" or whatever it calls Video Levels, and then check all the settings.
Thanks for clarifying full range vs limited range. While the definitions are well known and seemingly straightforward, sometimes things may seem to be working "backwards" if one doesn't think it through carefully.

Not that I have anything against passthrough, but personally I haven't found BTB to be essential for setting contrast. I just posted my view in a different thread earlier today:

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post #10 of 45 Old 09-08-2015, 06:23 PM
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Quote:
Originally Posted by virtualrain View Post
Thank you very much, I'll try some things this evening. I don't care about desktop crush as my Mac is exclusive to Plex/Kodi (I'm still trying to figure out which player is better).

My TV has the following settings...

Quote:
The HDMI® Dynamic Range feature helps produce natural color by changing the luminance tone reproduction of HDMI input color signals. The dynamic range of the image is reproduced properly by selecting the desired dynamic range for signal type being used.
Use the Auto setting during normal operation. The Auto setting automatically selects the dynamic range Full or Limited based on dynamic range information coming from connected device.
The Full setting should be used when you would like the signal range fixed to full range. An example may be a high-definition signal from a device connected using an HDMI cable.
Limited: The signal range is fixed to limited range. This should be used when less color is desired.
Wow. I doubt those instructions have anything to do with reality. Per google, Thanks Sony. Below, I'm going to assume Full/Limited have their usual meaning.

Quote:
If I want to go the passthrough route to preserver WTW and BTB, should I be using Full or Limited?
For the passthrough option I talked about, you would choose Limited, because that's what your player is outputting. If your player were outputting Full Range, it would have already discarded BTB/WTW in the expansion from Limited Range aka Video Levels to Full Range aka PC Levels. Only when the player is outputting Video Levels can there be BTB/WTW. Again, the video card must be outputting Full Range RGB 0-255 for this to work, and I'm talking about the setting that affects all output. If there is a separate "Video" section, ideally it would be left at "Let the player decide" or whatever they call it. In summary, the idea for passthrough is to set the player up to decode the video without altering the pixel values and for the card to output those pixels without altering them. This means Limited Range for the player and Full Range for the card.

Quote:
EDIT: Never mind... I found this, which explains the TV settings more clearly...

http://forum.kodi.tv/showthread.php?...501#pid1995501
And crawfish even rhymes with sawfish. Hmmmm.
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post #11 of 45 Old 09-08-2015, 08:38 PM - Thread Starter
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Originally Posted by sawfish View Post

And crawfish even rhymes with sawfish. Hmmmm.

Ha! Sorry... I thought that was you!

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post #12 of 45 Old 09-08-2015, 11:49 PM - Thread Starter
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Quote:
Originally Posted by sawfish View Post

For the passthrough option I talked about, you would choose Limited, because that's what your player is outputting. If your player were outputting Full Range, it would have already discarded BTB/WTW in the expansion from Limited Range aka Video Levels to Full Range aka PC Levels. Only when the player is outputting Video Levels can there be BTB/WTW. Again, the video card must be outputting Full Range RGB 0-255 for this to work, and I'm talking about the setting that affects all output. If there is a separate "Video" section, ideally it would be left at "Let the player decide" or whatever they call it. In summary, the idea for passthrough is to set the player up to decode the video without altering the pixel values and for the card to output those pixels without altering them. This means Limited Range for the player and Full Range for the card.
Thanks again for your help.

This evening I set Kodi (running on OpenELEC on my Mac Mini) to limited range, and the TV to limited range and was dismayed to find I still wasn't getting WTW and BTB on the test patterns. They were still getting clipped. So I thought I would look into ensuring the OpenELEC GPU driver was set for full RGB colour range and came across this thread (last post) which pointed out another setting in Kodi that needs to be disabled (VAAPI Render Method). Sure enough, toggling that did the trick. I've now calibrated my TV's black point properly and get full WTW on max contrast.

I suspect 99% of people using HTPCs are probably running with non-ideal settings as a result of all this nonsense that's very poorly documented anywhere.

Now that I have my TV setup properly for Kodi. What am I likely going to run into when running my PS4 through the AVR to the same TV input? Any advice on how to setup my PS4 to use the same TV settings on the same TV input? I believe the PS4 has both a Limited and Full color range option as well. Will the TV set to limited mean games won't look good? Unfortunately, the Limited/Full range setting on the TV is a per input setting, not a picture mode setting.

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post #13 of 45 Old 09-09-2015, 08:53 AM
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Originally Posted by virtualrain View Post
I suspect 99% of people using HTPCs are probably running with non-ideal settings as a result of all this nonsense that's very poorly documented anywhere.
I don't doubt it. The terminology is confusing at best and often used ambiguously, which doesn't help.

Quote:
Now that I have my TV setup properly for Kodi. What am I likely going to run into when running my PS4 through the AVR to the same TV input? Any advice on how to setup my PS4 to use the same TV settings on the same TV input? I believe the PS4 has both a Limited and Full color range option as well. Will the TV set to limited mean games won't look good? Unfortunately, the Limited/Full range setting on the TV is a per input setting, not a picture mode setting.
I don't do PS4 so can't really advise on that. The holy grail is an AVR with two HDMI outputs, one you can use for Video Levels and the other for PC Levels, like my Pioneer VSX-1124. OTOH, if everything has to go to a single TV input, and one or more devices do best outputting PC Levels (black = 0, white = 255), the compromise approach for the HTPC may be the best bet, that is, having the video player expand Video Levels to PC Levels. Lots of people do just that.
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post #14 of 45 Old 09-09-2015, 10:16 AM
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Originally Posted by virtualrain View Post
Now that I have my TV setup properly for Kodi. What am I likely going to run into when running my PS4 through the AVR to the same TV input?
The default setting on the PS4 is "automatic", it would be best to set it manually to "Limited".
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Originally Posted by Dominic Chan View Post
The default setting on the PS4 is "automatic", it would be best to set it manually to "Limited".
Why do you suggest this? (not disagreeing, just trying to understand what's going on when you set it one way or the other)

Edit: I use the PS4 for gaming, not watching movies. I would expect games to use the full RGB range... No?

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Originally Posted by sawfish View Post
I don't doubt it. The terminology is confusing at best and often used ambiguously, which doesn't help.

I don't do PS4 so can't really advise on that. The holy grail is an AVR with two HDMI outputs, one you can use for Video Levels and the other for PC Levels, like my Pioneer VSX-1124. OTOH, if everything has to go to a single TV input, and one or more devices do best outputting PC Levels (black = 0, white = 255), the compromise approach for the HTPC may be the best bet, that is, having the video player expand Video Levels to PC Levels. Lots of people do just that.
Great idea. I have two HDMI outputs on my new Yamaha AVR. I can use the existing one for video levels with Kodi and the other with full RGB for gaming.
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I came across this article about levels and gaming consoles, which I thought was good until I read this, which seems out of date... Most modern TVs work just fine in full RGB mode, and have no trouble reproducing the full range... No?

http://referencehometheater.com/2014...ll-vs-limited/

Quote:
Q: My TV supports Full mode, shouldn’t I use this?

A: No. TVs support Full to make them easier to calibrate. Most TVs will not display a black level below 16 because video content should never have it. By letting you see Black 15 or 14, it can make it easier to calibrate the display and get the black level correct. However, you really should not use this as your main setting as most displays are not designed to display levels below 16, and often introduce color tints when doing white levels past 240 or so. Additionally, if you restrict yourself to levels 16-235 you wind up with a brighter image with a better contrast ratio, as you can turn up the contrast level higher. Contrast Ratio is the thing your eye notices most, and so it will produce a more pleasing image.

Also, since any non-video game content will only use 16-235, these picture settings will work for all inputs and sources, not just a single source.
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Originally Posted by virtualrain View Post
I came across this article about levels and gaming consoles, which I thought was good until I read this, which seems out of date... Most modern TVs work just fine in full RGB mode, and have no trouble reproducing the full range... No?

http://referencehometheater.com/2014...ll-vs-limited/
You conclude correctly.
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post #19 of 45 Old 09-10-2015, 07:26 AM
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Quote:
Originally Posted by virtualrain View Post
I came across this article about levels and gaming consoles, which I thought was good until I read this, which seems out of date... Most modern TVs work just fine in full RGB mode, and have no trouble reproducing the full range... No?
IMHO, that article actually contains some errors:

Quote:
TVs support Full to make them easier to calibrate...By letting you see Black 15 or 14, it can make it easier to calibrate the display
Full mode does not display BTB; Limited mode does. Some people find it easier to set the Brightness control if they can see BTB during calibration.

Quote:
Additionally, if you restrict yourself to levels 16-235 you wind up with a brighter image with a better contrast ratio, as you can turn up the contrast level higher.
Limited mode actually produces a dimmer image, hence worse (lower) contrast ratio, if you follow the usual calibration approach, which reserves some headroom to allow for WTW. White the contrast level setting may indeed by higher, it's not receiving the "full" signal which more than negates the higher setting.

Last edited by Dominic Chan; 09-10-2015 at 07:28 AM. Reason: Corrected typo BTW-> BTB
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Originally Posted by Dominic Chan View Post
IMHO, that article actually contains some errors...

Full mode does not display BTB; Limited mode does.
It's pretty unfortunate terminology, isn't it? When talking about video, "Limited Range" is the default and passthrough, or lossless, or whatever synonym you prefer, while "Full Range" discards information and scales values as it expands 16-235 to 0-255, the discarded values being BTB (< 16) and WTW (> 235). The word "Full" sounds better than and thus preferable to "Limited", but it isn't here. I think it's clearer to use "Video Levels" and "PC Levels" in this context, where "Levels" means the values considered to be reference black and white.

When talking about video card output, it's the other way around. The default is "Full Range RGB", 0-255, or passthrough, or lossless, or whatever synonym you prefer, while "Limited Range RGB" is 16-235 and implies that 0-255 is compressed to the range 16-235. So for video card output, "Full" really is better than "Limited".

When talking about TVs and other devices, each manufacturer is its own universe. For example, my Panasonic ST60 uses "Standard" and "Non-standard" for Video Levels and PC Levels, respectively, which is pretty good. OTOH, the Apple TV uses "RGB High" to mean Video Levels and "RGB Low" to mean PC Levels. Argggh!
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post #21 of 45 Old 09-10-2015, 08:07 PM - Thread Starter
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^^^ That's a very good summary of what the issues are for new-comers to this.

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post #22 of 45 Old 09-10-2015, 09:22 PM - Thread Starter
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Here's a good post I came across related to the PS3 from someone who knows what they are talking about. It's incredible the amount of mis-information passed around by many in gaming forums.

Quote:
I'm just going to copy and paste my own comments from one of the other times this came up.

The RGB full/limited settings are poorly described. It should be labeled as PC levels (0 to 255) and video levels (16 to 235)

The PS3 simply remaps the values depending on the setting (for gaming, the RGB setting is completely ignored for movies)

A calibrated tv expecting video levels and receiving video levels from a PS3 will look the same as a calibrated tv expecting PC levels and receiving PC levels from the PS3.

If you are using a tv though even if it accepts PC levels you would be better off using limited and calibrating accordingly. Otherwise if you use your display for movies or tv your display will be calibrated for PC levels and everything would be off unless you kept a separate set of settings and constantly switched between them.

If you mix and match your settings you will end up with crushed blacks and other color inaccuracies. Your settings should be limited, superwhite on, and under BD / DVD Video Output Format (HDMI) you should take it out of auto and set it manually to Y Pb / Cb Pr / Cr.

The manual setting in conjunction with superwhite on is the only way to get it to pass WTW and BTB due to a bug that I'm not sure if it was ever fixed. Blu-ray is natively YCC anyway and this is the reason for movies the PS3 ignores any limited or full settings so there is no reason not to manually be set to YCC in the first place.


So in short. RGB is meaningless when it comes to blu-ray movies as it is completely ignored by the PS3.

For gaming you can achieve results in both PC output and video output however if you calibrate for PC levels you will have to make sure you have a separate setting for movies and tv viewing on your display (if you use your display for that)

Lastly all of this is a moot point if you are using some out of the box setting like standard or vivid (torch mode) because you have inaccuracies all over the place anyway.
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post #23 of 45 Old 09-10-2015, 09:51 PM
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If you can use YCrCb 4:4:4 (or 4:2:2 / 4:2:0), that will avoid the RGB full vs limited vs other terminology confusion. That seems worthwhile all by itself.
Also most video formats (ie, DVD, BluRay, streams) use it, so most HT displays expect and do best with that display format as well.

Computer games and computer displays work best with RGB full aka 0-255 levels.
You will certainly get more contrast from that than from using the RGB limited settings.

However, when you play video content, you have to be aware of the difference and have the player and display match up, or maybe pray that the "auto" setting works reliably.

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post #24 of 45 Old 09-19-2015, 03:58 PM - Thread Starter
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Quote:
Originally Posted by cswiger View Post
If you can use YCrCb 4:4:4 (or 4:2:2 / 4:2:0), that will avoid the RGB full vs limited vs other terminology confusion. That seems worthwhile all by itself.
Also most video formats (ie, DVD, BluRay, streams) use it, so most HT displays expect and do best with that display format as well.

Computer games and computer displays work best with RGB full aka 0-255 levels.
You will certainly get more contrast from that than from using the RGB limited settings.

However, when you play video content, you have to be aware of the difference and have the player and display match up, or maybe pray that the "auto" setting works reliably.
Don't disagree. My TV (like most) only supports 4:4:4 on the game and graphics (PC) picture modes... which offer no motion compensation so that display mode is not ideal for movie content for a couple of reasons.

The ideal solution I have found is to setup one input on the TV for video levels and another for full RGB. I use the Cinema Pro mode on my Sony XBR on limited for 24p content and Game mode at full for PS4 gaming (which also offers minimum input lag).

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post #25 of 45 Old 09-19-2015, 04:15 PM - Thread Starter
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Further to this thread and video level optimization with Kodi, I've discovered that by default, the Kodi GPU is not running in Full mode. It's set to Automatic, which actually defaults to Limited 16-235, resulting in undesirable output.

I'd like to hear from others on this...

If you're using Kodi on OpenELEC (or Linux I guess), you need to set it up to force full RGB on boot by adding an autostart.sh file.

You can determine what mode it's running in as follows:
- Make sure SSH is enabled in OE
- ssh root@IP.address
- password: openelec
- type: xrandr --verbose (to see the GPU settings)
- look for the HDMI input with a display attached - note the Broadcast RGB setting

To over-ride the GPU setting, create an autostart.sh file as follows:

cd /storage/.config
rm autostart.sh
vi autostart.sh
<i> (to insert)
copy and paste (don't try to type this)...

Code:
#!/bin/sh
OUTPUT=`xrandr -q | sed '/ connected/!d;s/ .*//;q'`
xrandr --output $OUTPUT --set "Broadcast RGB" "Full"
Hit ESC
type :wq <enter>
chmod +x autostart.sh
reboot

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post #26 of 45 Old 09-22-2015, 11:28 PM
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-edit-

Okay, I got this to work. I still could not figure out how to copy the code into the Window, but strangely right clicking the mouse put most of the text there. I just typed in the rest.

Also, I didn't realize I had left out the : before the "wq" and that was clearly important.

Thanks!

B.

Last edited by Brian B; 09-28-2015 at 07:40 PM. Reason: New Info
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post #27 of 45 Old 09-22-2015, 11:44 PM - Thread Starter
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Originally Posted by Brian B View Post
Would like to try this, but when I "cd /storage/.config" ....it says I don't have a storage directory. (I do see .config when I do a directory listing.)

Also, there is no autostart.sh file...

Something else I need to do?

B.

I didn't have an auto start either. Just cd to .config then and create it there. I'll double check the path later... Maybe I'm missing a dot or something.

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post #28 of 45 Old 09-23-2015, 06:13 AM
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Quote:
Originally Posted by cswiger View Post
If you can use YCrCb 4:4:4 (or 4:2:2 / 4:2:0), that will avoid the RGB full vs limited vs other terminology confusion. That seems worthwhile all by itself.
Also most video formats (ie, DVD, BluRay, streams) use it, so most HT displays expect and do best with that display format as well.
It is not so easy. With windows OS if you set YCbCr as the output the flow with films will be:

YCbCr 4:2:0 -> YCbCr 4:2:2 -> YCbCr 4:4:4 -> RGB 16-235 -> RGB 0-255 -> RGB 16-235 -> YCbCr 4:4:4 (-> YCbCr 4:2:2)

If you set RGB 0-255 as output in the GPU and the renderer in RGB 16-235 the flow will be:

YCbCr 4:2:0 -> YCbCr 4:2:2 -> YCbCr 4:4:4 -> RGB 16-235

I don't know if this is true with linux.

sawfish has explained perfectly all the RGB levels - TV black levels configuration.
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post #29 of 45 Old 09-23-2015, 12:02 PM
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Quote:
Originally Posted by HDANDMORE View Post
It is not so easy. With windows OS if you set YCbCr as the output the flow with films will be:

YCbCr 4:2:0 -> YCbCr 4:2:2 -> YCbCr 4:4:4 -> RGB 16-235 -> RGB 0-255 -> RGB 16-235 -> YCbCr 4:4:4 (-> YCbCr 4:2:2)

If you set RGB 0-255 as output in the GPU and the renderer in RGB 16-235 the flow will be:

YCbCr 4:2:0 -> YCbCr 4:2:2 -> YCbCr 4:4:4 -> RGB 16-235

I don't know if this is true with linux.

sawfish has explained perfectly all the RGB levels - TV black levels configuration.
Hmm. The conversion chains you've suggested would be highly suboptimal due to the lossy steps, but such steps shouldn't be required unless you're choosing poorly with your filter stages?

If you're running in windowed mode, then video might be converted from YCbCr 4:2:0 directly to RGB 0-255 via video hardware (ie, see nppiYCbCr420ToRGB_8u_P3C3R from the nVidia CUDA docs, or similar for ATI), or it might be chroma upsampled from YCbCr 4:2:0 to YCbCr 4:4:4 via madVR or whichever. If your output is set to RGB limited, then yes, you'll get the lossy RGB 0-255 -> RGB 16-235 compression; but otherwise you'd be sending either RGB 0-255 or YCbCr 4:4:4 to the display depending on which output format you set.

If you're running in fullscreen exclusive mode, then you shouldn't have to convert YCbCr 4:2:0 to RGB unless you set your output format to RGB. I'm trying to find signs of whether YCbCr 4:2:0 direct passthrough to a display set for YCbCr 4:4:4 is possible, but I'm getting too many matches with questions and not enough with answers. :-)

Still found some useful links like:

https://forum.doom9.org/showthread.php?t=171787 # madVR rendering options and diagram

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post #30 of 45 Old 09-23-2015, 02:02 PM
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Quote:
Originally Posted by cswiger View Post
If you're running in fullscreen exclusive mode, then you shouldn't have to convert YCbCr 4:2:0 to RGB unless you set your output format to RGB. I'm trying to find signs of whether YCbCr 4:2:0 direct passthrough to a display set for YCbCr 4:4:4 is possible, but I'm getting too many matches with questions and not enough with answers. :-)
Per madshi:

http://madshi.net/htpc/page4.html
Quote:
However, YCbCr output makes sense only if it's a "pure" output, without a multitude of conversions in between. If the graphics card first converts the YCbCr source to RGB, then converts it back to YCbCr for output this is actually a negative thing. Ideally the graphics card should just take the YCbCr source and output it as it is. To my best knowledge no graphics card on the market can do this today.
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