Official JVC RS600 / RS500 (X950R / X750R - X9000 / X7000) Owners Thread - Page 956 - AVS Forum | Home Theater Discussions And Reviews
Forum Jump: 
 84660Likes
Reply
 
Thread Tools
post #28651 of 31899 Old 02-01-2018, 05:18 AM
AVS Forum Special Member
 
Manni01's Avatar
 
Join Date: Sep 2008
Posts: 8,978
Mentioned: 307 Post(s)
Tagged: 0 Thread(s)
Quoted: 5335 Post(s)
Liked: 5370
Quote:
Originally Posted by madshi View Post
We haven't even seriously tried yet! I've only implemented one general scientific tone mapping curve, without any real tweaks/modifications aimed at projectors yet. Please don't give up so quickly! Let's try to achieve the best scientific solution first, and only after we've seriously tried that and failed, it would be time to admit defeat and look for alternatives.
Not giving up at all, but unless we can input the actual peakY and dynamically adjust the internal PeakY according to content, I don't think there will be a satisfying result for all titles. The custom curves I'm using are 100% scientific, they do follow Bt2390, it's just that they are optimized according to content in order to get the best of both worlds. They are not "pie in the sky let's tune to taste so that it looks like I want" curves. Not at all. My understanding is that Arve is using a BT2390 formula with a few more tweaks, but you can decide where to hard clip and use the available range in an optimum way.

EDIT: I thought there was a parameter for max_brightness of the content (distinct from the max_brightness of the display) in BT2390. Did you try feeding it with MaxCLL (once you have ascertained MaxCLL was valid, as per the algo above or similar)?

JVC Autocal Software V11 Calibration for 2019 Models
Batch Utility V4.02 May 16 2019 to automate measurements files for madVR with support for BD Folders

Last edited by Manni01; 02-01-2018 at 05:41 AM.
Manni01 is offline  
Sponsored Links
Advertisement
 
post #28652 of 31899 Old 02-01-2018, 05:41 AM
AVS Forum Special Member
 
madshi's Avatar
 
Join Date: May 2005
Posts: 7,571
Mentioned: 456 Post(s)
Tagged: 0 Thread(s)
Quoted: 2330 Post(s)
Liked: 2996
Quote:
Originally Posted by Manni01 View Post
Not giving up at all, but unless we can input the actual peakY and dynamically adjust the internal PeakY according to content, I don't think there will be a satisfying result for all titles.
If madVR has all the necessary information (truthfully measured peakY of your display, measured peakY of each video frame), then why should it not be possible for madVR to achieve a satisfying result for all titles? madVR already has all that info. Probably just some tweaks to the tone mapping parameters are needed, that's all.

I'd say, once a new madVR build is out and you find more time for testing, maybe you can make a couple of very small movie samples available to me that showcase what is not to like with the current tone mapping behaviour, if you input the true measured peak luminance of 120nits, and then I can try tweaking the tone mapping behaviour accordingly. Let's see how far that takes us.
Tom Bley, nathan_h, muzz and 5 others like this.
madshi is offline  
post #28653 of 31899 Old 02-01-2018, 05:58 AM
AVS Forum Special Member
 
Manni01's Avatar
 
Join Date: Sep 2008
Posts: 8,978
Mentioned: 307 Post(s)
Tagged: 0 Thread(s)
Quoted: 5335 Post(s)
Liked: 5370
Quote:
Originally Posted by madshi View Post
If madVR has all the necessary information (truthfully measured peakY of your display, measured peakY of each video frame), then why should it not be possible for madVR to achieve a satisfying result for all titles? madVR already has all that info. Probably just some tweaks to the tone mapping parameters are needed, that's all.

I'd say, once a new madVR build is out and you find more time for testing, maybe you can make a couple of very small movie samples available to me that showcase what is not to like with the current tone mapping behaviour, if you input the true measured peak luminance of 120nits, and then I can try tweaking the tone mapping behaviour accordingly. Let's see how far that takes us.
Because when you truthfully measure the peakY of each frame you can't adjust as much as you should without producing flicker (too wide variations in brightness) as you said yourself. You have no way when you start playing the file to know whether the content will shoot above 1100nits or not.

Did you see my edit above? I thought ST2390 had a parameter in the formula for max_brightness of the content. That might be what's missing? Could you share the parameters you have implemented? It might be useful to make some of them accessible in the next build, at least during testing.

I don't think I'll be able to make short clips but if you send me the list of the titles you have I can give you examples from that list with timecodes/chapters. The Revenant, Mad Max, Pacific Rim, Deadpool, The Shallows, Batman vs Superman should be enough.

Happy to start with actual peakY, I agree that it would be the ideal way to proceed, but I think you will need a checkbox for projectors (in dedicated room), because while it makes sense to follow the curve up to 100nits for displays with ambient light and a peakY of at least 600nits, because in that case reference white =100nits if you want to be correct, for projectors in a dedicated room reference white = 50nits and not 100nits, so it doesn't make sense to do it the same way as following the absolute curve religiously isn't accurate or desirable. BT2390 accounts for that in part, but not completely as far as I can see. Being able to specify (or ideally extract from the metadata) the max brightness of the content and the value for reference white (or brightness factor) would help a lot to get better results with projectors specifically.

Looking forward to testing the next build

JVC Autocal Software V11 Calibration for 2019 Models
Batch Utility V4.02 May 16 2019 to automate measurements files for madVR with support for BD Folders

Last edited by Manni01; 02-01-2018 at 06:06 AM.
Manni01 is offline  
Sponsored Links
Advertisement
 
post #28654 of 31899 Old 02-01-2018, 06:14 AM
AVS Forum Special Member
 
madshi's Avatar
 
Join Date: May 2005
Posts: 7,571
Mentioned: 456 Post(s)
Tagged: 0 Thread(s)
Quoted: 2330 Post(s)
Liked: 2996
Quote:
Originally Posted by Manni01 View Post
Because when you truthfully measure the peakY of each frame you can't adjust as much as you should without producing flicker (too wide variations in brightness) as you said yourself.
And as I said, I'm using a rolling average which nicely takes care of flickering. I see no use in maxCLL, because not all titles have it, because it might be incorrect, because it's probably static for the whole movie, and because I can measure myself frame by frame, which should be greatly superior. I should easily be able to provide all the benefits of HDR10+ with current HDR10 content. Anyway, let's continue this in the doom9 thread later...
madshi is offline  
post #28655 of 31899 Old 02-01-2018, 06:25 AM
AVS Forum Special Member
 
Manni01's Avatar
 
Join Date: Sep 2008
Posts: 8,978
Mentioned: 307 Post(s)
Tagged: 0 Thread(s)
Quoted: 5335 Post(s)
Liked: 5370
Quote:
Originally Posted by madshi View Post
And as I said, I'm using a rolling average which nicely takes care of flickering. I see no use in maxCLL, because not all titles have it, because it might be incorrect, because it's probably static for the whole movie, and because I can measure myself frame by frame, which should be greatly superior. I should easily be able to provide all the benefits of HDR10+ with current HDR10 content. Anyway, let's continue this in the doom9 thread later...
This is what I thought when I did my initial testing with 1000-1100nits titles, as I could see superb benefits and no downsides. I agree that of course this is the preferable way to do it if it works equally well with all content. Unfortunately, that's not what I see with 4000nits titles if I use a setting giving the best results for 1100nits titles.

Let's discuss indeed in the doom9 thread when the next build is available.

JVC Autocal Software V11 Calibration for 2019 Models
Batch Utility V4.02 May 16 2019 to automate measurements files for madVR with support for BD Folders
Manni01 is offline  
post #28656 of 31899 Old 02-01-2018, 07:46 AM
AVS Forum Addicted Member
 
stanger89's Avatar
 
Join Date: Nov 2002
Location: Marion, IA
Posts: 23,130
Mentioned: 34 Post(s)
Tagged: 0 Thread(s)
Quoted: 4156 Post(s)
Liked: 2384
Quote:
Originally Posted by madshi View Post
IMHO the best (most scientific) approach would be to tell madVR the true measurement of your display's peak Y value, and then leave the rest in madVR's hands. That's the only way madVR even has a chance to reproduce the important low end (e.g. 0-25 Nits) faithfully. If that doesn't produce good enough results right now, let's work together on improving that.
One thing to consider is that we probably don't want to "faithfully" reproduce anything on a projector. SDR is assumed to be 100 nits, however with projectors we generally calibrate it to half that. The best luck we've had with HDR is to calibrate to some factor/fraction of what ST.2084 actually calls for. Perhaps what we need is to be able to tell madVR our true peakY and also some scale factor to apply.

The "problem" I noticed with low (more "accurate") PeakY values in madVR is that the overall image is way, way, way too bright. I started out with peakY set to 200, while my projector can really only do about 100. The result is that the mid tones seemed probably twice as bright as an SDR image, when they're really supposed to be about the same. I can't remember if I've got it at 300 or 400 now, but HDR still seems brighter than SDR, and I'm not talking highlights, but the overall tone.
stanger89 is offline  
post #28657 of 31899 Old 02-01-2018, 08:08 AM
AVS Forum Special Member
 
madshi's Avatar
 
Join Date: May 2005
Posts: 7,571
Mentioned: 456 Post(s)
Tagged: 0 Thread(s)
Quoted: 2330 Post(s)
Liked: 2996
Fair enough. I was planning to add some more controls to allow users to "fine tune" the tone mapping. Some sort of "scale factor" would be an option, I guess.
nathan_h, stevenjw, stef2 and 3 others like this.
madshi is offline  
post #28658 of 31899 Old 02-01-2018, 08:17 AM
AVS Forum Addicted Member
 
stanger89's Avatar
 
Join Date: Nov 2002
Location: Marion, IA
Posts: 23,130
Mentioned: 34 Post(s)
Tagged: 0 Thread(s)
Quoted: 4156 Post(s)
Liked: 2384
Quote:
Originally Posted by madshi View Post
Fair enough. I was planning to add some more controls to allow users to "fine tune" the tone mapping. Some sort of "scale factor" would be an option, I guess.
Perhaps there's a better way, I'm not really sure what Lumagen or Oppo are actually doing, they seem to both get rave reviews, but it seems like we should acknowledge that with projectors we don't need to try to retain (for example) medium gray (18%/18 nits SDR and 18 nits on a flat panel), when we'd normally calibrate a projector to about half that.
stanger89 is offline  
post #28659 of 31899 Old 02-01-2018, 08:22 AM
AVS Forum Special Member
 
madshi's Avatar
 
Join Date: May 2005
Posts: 7,571
Mentioned: 456 Post(s)
Tagged: 0 Thread(s)
Quoted: 2330 Post(s)
Liked: 2996
Well, I do like to do things scientifically (if possible). So if the UHD Blu-Ray asks for a pixel to be displayed with 20 Nits, I would like to achieve that, and madVR actually does. However, as you say, due to projectors being rather dim, and because they're usually used without any ambient light, the rules are somewhat different, so some sort of scaling factor does make sense. What I don't want to do is to throw science completely out the window and just hand draw some curve which seems pleasing for some titles.
AidenL likes this.
madshi is offline  
post #28660 of 31899 Old 02-01-2018, 08:34 AM
Advanced Member
 
Join Date: Dec 2015
Posts: 865
Mentioned: 4 Post(s)
Tagged: 0 Thread(s)
Quoted: 552 Post(s)
Liked: 298
You guys are mad scientist i like it.. Keep going I'm sure with time you will be able to come up with one curve for everything.. Might not be today but with time you will, watch...
jorgebetancourt is online now  
post #28661 of 31899 Old 02-01-2018, 08:43 AM
AVS Forum Special Member
 
nathan_h's Avatar
 
Join Date: Mar 2001
Posts: 9,326
Mentioned: 43 Post(s)
Tagged: 0 Thread(s)
Quoted: 2724 Post(s)
Liked: 1955
Quote:
Originally Posted by madshi View Post
Well, I do like to do things scientifically (if possible). So if the UHD Blu-Ray asks for a pixel to be displayed with 20 Nits, I would like to achieve that, and madVR actually does. However, as you say, due to projectors being rather dim, and because they're usually used without any ambient light, the rules are somewhat different, so some sort of scaling factor does make sense. What I don't want to do is to throw science completely out the window and just hand draw some curve which seems pleasing for some titles.
That's a fair point. There are a few scientific hints for what a projector should do in the SDR realm (ie, 100 ire is defined as half as bright on a projector as a flat panel) and that points at a standard for adapting definitions created for HDR on flat panels to HDR on a projector (eg, that diffuse white should be half as many measured FTL on a projector in a dark room to look "equivalent" to a flat panel in a living room/lounge).
nathan_h is offline  
post #28662 of 31899 Old 02-01-2018, 08:53 AM
Member
 
rrebello's Avatar
 
Join Date: Feb 2013
Posts: 78
Mentioned: 1 Post(s)
Tagged: 0 Thread(s)
Quoted: 43 Post(s)
Liked: 45
Quote:
Originally Posted by nohjy View Post
I just purchased a UB900 to use with my RS600 and now it appears the OPPO is the way to go. Can someone tell me what I would gain by buying the OPPO. ? Is there anything the UB900 does better at this point?
Please see Manni's post. My journey was as follows. Bought an OPPO, I tried to the stripped Meta data (blacks were crushed on the Oppo). I then made a custom curve (not very good) and downloaded 10 different custom curves from others (some were pretty good for my set-up but always a little too dim even at high lamp mode). I was never satisfied with the picture overall. I went an bought a Panny with HDFury Integral. It was better (more consistent on brightness) but did not have the same look at my OLED (bright highlight, colors not as saturated). Additionally, all of the HDR content from my Roku was always too dark with the custom curves. I could not even watch Netflix HDR with the Panny slider adjustment. I got on the waiting list for ChadB but when he came to Atlanta in the Fall, I did not make the cut for his visit (waiting 8 months now).

So, I have been using the Panny / HDFury Integral with the Oppo on the shelf. With this latest Oppo release, I swapped everything. Discs and Roku look great. I watched the lastest Blade Runner streaming UHD & HDR from VUDU through the Oppo and it looked great! I finally have the projector with the best SDR and HDR that I thought I was buying in 2016. It has been a 1 1/2 years and I have wasted a bunch of time, and money (Panny/Integral). For me, the OPPO has brought me back to state of the art SDR and HDR (disc and streaming) for projectors. Is it perfect? Probably not. Am I thrilled finally? YES.
Dave Harper, muzz, OzHDHT and 4 others like this.
rrebello is offline  
post #28663 of 31899 Old 02-01-2018, 10:08 AM
AVS Forum Special Member
 
madshi's Avatar
 
Join Date: May 2005
Posts: 7,571
Mentioned: 456 Post(s)
Tagged: 0 Thread(s)
Quoted: 2330 Post(s)
Liked: 2996
Quote:
Originally Posted by nathan_h View Post
That's a fair point. There are a few scientific hints for what a projector should do in the SDR realm (ie, 100 ire is defined as half as bright on a projector as a flat panel) and that points at a standard for adapting definitions created for HDR on flat panels to HDR on a projector (eg, that diffuse white should be half as many measured FTL on a projector in a dark room to look "equivalent" to a flat panel in a living room/lounge).
Ok, I suppose I could add a "diffuse white target" option which defaults to "flat panel -> 100 nits". Would it make sense to design the option like that?

If so, and if you then change that option to "projector -> 50 nits", I should probably simply half all pixel nits values? E.g. if then the UHD Blu-Ray asks for a pixel to be 30 nits bright, I should reproduce it with 15 nits instead? Or would the "scaling factor" be non-linear in some way?

Quote:
Originally Posted by jorgebetancourt View Post
You guys are mad scientist
Haha, yeah, I'm mad(shi). That's why all my products start with "mad"...
madshi is offline  
post #28664 of 31899 Old 02-01-2018, 10:46 AM
AVS Forum Addicted Member
 
stanger89's Avatar
 
Join Date: Nov 2002
Location: Marion, IA
Posts: 23,130
Mentioned: 34 Post(s)
Tagged: 0 Thread(s)
Quoted: 4156 Post(s)
Liked: 2384
Quote:
Originally Posted by madshi View Post
Well, I do like to do things scientifically (if possible). So if the UHD Blu-Ray asks for a pixel to be displayed with 20 Nits, I would like to achieve that, and madVR actually does. However, as you say, due to projectors being rather dim, and because they're usually used without any ambient light, the rules are somewhat different, so some sort of scaling factor does make sense. What I don't want to do is to throw science completely out the window and just hand draw some curve which seems pleasing for some titles.
Oh, agreed, I don't like just going by hand/eye, if only because it invariably leads to not working "all the time". The closest thing to science we have to go on with HDR for projectors, is Dolby Cinema/Dolby Vision, which has a peak Y of 106 nits, which is basically equal to the diffuse white point of consumer HDR, but it still includes room for highlights.

Quote:
Originally Posted by madshi View Post
Ok, I suppose I could add a "diffuse white target" option which defaults to "flat panel -> 100 nits". Would it make sense to design the option like that?
I think that's a good option, that's actually how I use Arve's tool. I set the max brightness to my measured peak white, and then the reference white to something less than that.

Quote:
If so, and if you then change that option to "projector -> 50 nits", I should probably simply half all pixel nits values? E.g. if then the UHD Blu-Ray asks for a pixel to be 30 nits bright, I should reproduce it with 15 nits instead? Or would the "scaling factor" be non-linear in some way?
That seems like a good starting point, except, you'd basically end up with exactly what Arve's tool gives us at low brightness levels, and this is what people are "complaining" about.
stanger89 is offline  
post #28665 of 31899 Old 02-01-2018, 11:06 AM
AVS Forum Special Member
 
madshi's Avatar
 
Join Date: May 2005
Posts: 7,571
Mentioned: 456 Post(s)
Tagged: 0 Thread(s)
Quoted: 2330 Post(s)
Liked: 2996
Quote:
Originally Posted by stanger89 View Post
I think that's a good option, that's actually how I use Arve's tool. I set the max brightness to my measured peak white, and then the reference white to something less than that.
Is "diffuse white" or "reference white" a better name?

Quote:
Originally Posted by stanger89 View Post
That seems like a good starting point, except, you'd basically end up with exactly what Arve's tool gives us at low brightness levels, and this is what people are "complaining" about.
What complaints are there exactly? FWIW, the complaints could have many possible reasons. E.g. the gamma curve not having enough control/correction points, or the gamma processing having too low precision/bitdepth, or tone mapping screwing with hue or with saturation. None of these issues should apply to madVR (as far as I can say).

Some people may think that tone mapping just consists of applying some compression curve to the Y channel. Which is not true (if you want good quality).

Well, anyway, I'll add this option, and let's see what effect it will bring.
nathan_h and Soulnight like this.
madshi is offline  
post #28666 of 31899 Old 02-01-2018, 11:20 AM
AVS Forum Special Member
 
Join Date: Dec 2014
Location: Mississauga, ON, Canada
Posts: 6,295
Mentioned: 118 Post(s)
Tagged: 0 Thread(s)
Quoted: 4371 Post(s)
Liked: 1608
Quote:
Originally Posted by madshi View Post
If so, and if you then change that option to "projector -> 50 nits", I should probably simply half all pixel nits values? E.g. if then the UHD Blu-Ray asks for a pixel to be 30 nits bright, I should reproduce it with 15 nits instead? Or would the "scaling factor" be non-linear in some way?
In the latest version of HCFR, diffuse white corresponds to the luminance on the ST2084 curve at 50% stimulus, which is 92~94 nits depending on the mastering display.
Initially it scaled everything down linearly for lower diffuse white, but that shifts the clipping point up for a fixed luminance. In the latest version (v3.5), the roll off point is kept fixed while the diffuse white is scaled.
Dominic Chan is offline  
post #28667 of 31899 Old 02-01-2018, 11:29 AM
AVS Forum Special Member
 
madshi's Avatar
 
Join Date: May 2005
Posts: 7,571
Mentioned: 456 Post(s)
Tagged: 0 Thread(s)
Quoted: 2330 Post(s)
Liked: 2996
Quote:
Originally Posted by Dominic Chan View Post
Initially it scaled everything down linearly for lower diffuse white, but that shifts the clipping point up for a fixed luminance. In the latest version (v3.5), the roll off point is kept fixed while the diffuse white is scaled.
I'm not sure I understand the comment about the clipping point for a fixed luminance. With "roll off point" you mean the compression curve "knee start", meaning the nits value at which the compression curve starts to do work? So you're saying that if the knee start is at e.g. 20 Nits with a 100 Nits diffuse white, then the knee still stays at 20 Nits, even if diffuse white is set to 50 Nits instead?
madshi is offline  
post #28668 of 31899 Old 02-01-2018, 11:32 AM
AVS Forum Addicted Member
 
stanger89's Avatar
 
Join Date: Nov 2002
Location: Marion, IA
Posts: 23,130
Mentioned: 34 Post(s)
Tagged: 0 Thread(s)
Quoted: 4156 Post(s)
Liked: 2384
Quote:
Originally Posted by madshi View Post
Is "diffuse white" or "reference white" a better name?
My vote would be reference white.

Quote:
What complaints are there exactly?
I know Kris reported that he couldn't get the same sort of shadow detail and specifically saturation in shadows with a custom curve as with his Lumagen's Intensity Mapping or the new Oppo Tone Mapping. It seems some others who have seen both have found the same thing. I know Manni had a similar experience with custom curves vs madVR as it is today.

Quote:
FWIW, the complaints could have many possible reasons. E.g. the gamma curve not having enough control/correction points, or the gamma processing having too low precision/bitdepth, or tone mapping screwing with hue or with saturation. None of these issues should apply to madVR (as far as I can say).
Yeah, it is hard, the FWIW, as I understand it, the curve Arve's tool loads into the JVC is 256 steps, not just the 10 that you can manually define/adjust, so it should be better than trying manually.

Quote:
Well, anyway, I'll add this option, and let's see what effect it will bring.
Sounds great! I look forward to trying it.
stanger89 is offline  
post #28669 of 31899 Old 02-01-2018, 01:31 PM
Pip
Advanced Member
 
Pip's Avatar
 
Join Date: May 2001
Location: Pittsburgh, PA
Posts: 676
Mentioned: 2 Post(s)
Tagged: 0 Thread(s)
Quoted: 199 Post(s)
Liked: 86
Quote:
Originally Posted by Mojito View Post
I'm having issues with PJ (X7000) which seems to interfere with the other HDMI output of my AV processor (Yamaha 5100).
I have the following setup:
Yamaha 5100 AV processor.
Various sources, including Oppo 203, Xbox, Sat box connected to 5100
HDMI out 1 is connectd to JVC PJ
HDMI out 2 - to LG 4K TV
PJ is connects with a fiberoptic HDMI cable from Kramer: https://www.kramerav.com/Product/CP-AOCH/60

The problem I'm having is when I want to watch any source on TV with my PJ off, the TV cannot lock to the 5100. You can see flickering in cycles where it tries to lock the signals.
I think that this is due to the fact that the optical cable is active and there is some activity within the cable even with the turned off projector, which causes some interference between HDMI Out 1 and HDMI Out 2. This doesnt happen with a normal cable or if I unplug the optical cable from either the PJ or 5100.
I'm not sure which piece of my equipment is to blame for this, but it seems that even when PJ is off, the HDMI inputs remain active and powered causing the cable to be also active. As a reuslt Yamaha is trying constantly to lock with the PJ and while trying to lock, it flickers the HDMI out to TV.
Has anyone had any similar experience with optical cables or just similar experience? Is it possible to completely power off the HDMI outputs when PJ is off? Any other solutions?
BTW, I previousely had Celerity optical cable, which requires external power on the PJ side. I had the same issue there too, but I managed to build a device that cuts off the power to the cable when the PJ is turned off. That solved the problem.
Kramer cable doesnt requre external power, so this trick doesn't work anymore.

Sorry for answering this so late. I haven’t looked at this thread in quite a while.

This is a known issue much discussed in the cable threads. Happens with all active cables. It’s an HDCP issue. It should only occur when you are using both HDMI monitor outputs at the same time. The solution is to use only one monitor output – the one to the display you’re viewing. Your receiver gives you a choice of monitor 1, monitor 2, or both. With active cables, you can only use both at the same time if both displays are powered on.

Pip
Mojito likes this.
Pip is offline  
post #28670 of 31899 Old 02-01-2018, 01:50 PM
AVS Forum Special Member
 
Join Date: Dec 2014
Location: Mississauga, ON, Canada
Posts: 6,295
Mentioned: 118 Post(s)
Tagged: 0 Thread(s)
Quoted: 4371 Post(s)
Liked: 1608
Quote:
Originally Posted by madshi View Post
I'm not sure I understand the comment about the clipping point for a fixed luminance. With "roll off point" you mean the compression curve "knee start", meaning the nits value at which the compression curve starts to do work? So you're saying that if the knee start is at e.g. 20 Nits with a 100 Nits diffuse white, then the knee still stays at 20 Nits, even if diffuse white is set to 50 Nits instead?
The attached figure illustrates what I was referring to (no tone mapping assumed).
Assuming a display with peak luminance of 1000 nits, the ST2084 EOTF (yellow line) hard clips at 75% stimulus. If we a multiplier of 2 for the projector with linear scaling, the target EOTF shifts down to the dashed white line. At the same time, the hard clipping point will shift to 83%, essentially "wasting" of the luminance in the upper end as no stimulus above 75% will increase the output. A similar issue may exist when tone mapping curve is applied, if the the entire curve is scaled linearly.
Attached Thumbnails
Click image for larger version

Name:	ST2084.jpg
Views:	44
Size:	165.3 KB
ID:	2354922  

Last edited by Dominic Chan; 02-01-2018 at 01:55 PM.
Dominic Chan is offline  
post #28671 of 31899 Old 02-01-2018, 01:54 PM
AVS Forum Special Member
 
Join Date: Dec 2014
Location: Mississauga, ON, Canada
Posts: 6,295
Mentioned: 118 Post(s)
Tagged: 0 Thread(s)
Quoted: 4371 Post(s)
Liked: 1608
Quote:
Originally Posted by stanger89 View Post
My vote would be reference white.
I believe ST2390 uses the term "diffuse white" for 100 nits, in contrast with "specular white" (100 to 10000 nits).
Dominic Chan is offline  
post #28672 of 31899 Old 02-01-2018, 02:07 PM
AVS Forum Special Member
 
madshi's Avatar
 
Join Date: May 2005
Posts: 7,571
Mentioned: 456 Post(s)
Tagged: 0 Thread(s)
Quoted: 2330 Post(s)
Liked: 2996
Quote:
Originally Posted by Dominic Chan View Post
The attached figure illustrates what I was referring to (no tone mapping assumed).
Assuming a display with peak luminance of 1000 nits, the ST2084 EOTF (yellow line) hard clips at 75% stimulus. If we a multiplier of 2 for the projector with linear scaling, the target EOTF shifts down to the dashed white line. At the same time, the hard clipping point will shift to 83%, essentially "wasting" of the luminance in the upper end as no stimulus above 75% will increase the output. A similar issue may exist when tone mapping curve is applied, if the the entire curve is scaled linearly.
My plan was to first convert the video to linear light (1.0 = 10,000 Nits), and then simply multiply with e.g. 0.5 to account for projectors targetting a lower diffuse white Nits, and then apply tone mapping as usual, but in such a way that no luminance is wasted. So the brightest pixel in the frame (if it exceeds diffuse white) gets assigned 1.0 by tone mapping. Sounds ok to you?
madshi is offline  
post #28673 of 31899 Old 02-01-2018, 03:26 PM
AVS Forum Special Member
 
Join Date: Dec 2014
Location: Mississauga, ON, Canada
Posts: 6,295
Mentioned: 118 Post(s)
Tagged: 0 Thread(s)
Quoted: 4371 Post(s)
Liked: 1608
Quote:
Originally Posted by madshi View Post
My plan was to first convert the video to linear light (1.0 = 10,000 Nits), and then simply multiply with e.g. 0.5 to account for projectors targetting a lower diffuse white Nits, and then apply tone mapping as usual, but in such a way that no luminance is wasted.
That sounds right.

Quote:
So the brightest pixel in the frame (if it exceeds diffuse white) gets assigned 1.0 by tone mapping. Sounds ok to you?
I am not familiar this this approach. I didn’t think the objective of tone mapping is to expand every frame the peak luminance, even with a sliding average.
EDIT:
I believe the luminance at any input level should not be expanded beyond the "scaled PQ curve".
As an example, the luminance at 60% of the PQ curve is is 240 nits. Assuming a multiplier of 2 is being used (diffuse white = 94/2 = 47 nits) for a display with 200 nits peak luminance, a 60% input should not be expanded beyond 240/2= 120 nits. Put it another way, the contrast ratio between any two points after tone mapping should not exceed the contrast ratio without tone mapping.

Last edited by Dominic Chan; 02-01-2018 at 07:04 PM.
Dominic Chan is offline  
post #28674 of 31899 Old 02-01-2018, 04:33 PM
AVS Forum Special Member
 
nathan_h's Avatar
 
Join Date: Mar 2001
Posts: 9,326
Mentioned: 43 Post(s)
Tagged: 0 Thread(s)
Quoted: 2724 Post(s)
Liked: 1955
Quote:
Originally Posted by madshi View Post
Ok, I suppose I could add a "diffuse white target" option which defaults to "flat panel -> 100 nits". Would it make sense to design the option like that?

If so, and if you then change that option to "projector -> 50 nits", I should probably simply half all pixel nits values? E.g. if then the UHD Blu-Ray asks for a pixel to be 30 nits bright, I should reproduce it with 15 nits instead? Or would the "scaling factor" be non-linear in some way?
I think several responses above mine (like @Dominic Chan , @stanger89 ) are smarter about this than I am. I know just enough to be dangerous......

I suspect @Kris Deering has measured some of the better output he has been seeing via the Oppo and Lumagen, and those measurements might give you/us hints as well. And I am sure @Manni has measured things but he is busy earning a living right now And of course @Chad_b has lots of secret sauce and he shares A LOT of info with the community and might have some opinions for you.
nathan_h is offline  
post #28675 of 31899 Old 02-02-2018, 01:48 AM
AVS Forum Special Member
 
madshi's Avatar
 
Join Date: May 2005
Posts: 7,571
Mentioned: 456 Post(s)
Tagged: 0 Thread(s)
Quoted: 2330 Post(s)
Liked: 2996
Quote:
Originally Posted by Dominic Chan View Post
I am not familiar this this approach. I didn’t think the objective of tone mapping is to expand every frame the peak luminance, even with a sliding average.
The goal of this logic is to already deliver today what HDR10+ plans to achieve in the future.

Quote:
Originally Posted by Dominic Chan View Post
I believe the luminance at any input level should not be expanded beyond the "scaled PQ curve".
As an example, the luminance at 60% of the PQ curve is is 240 nits. Assuming a multiplier of 2 is being used (diffuse white = 94/2 = 47 nits) for a display with 200 nits peak luminance, a 60% input should not be expanded beyond 240/2= 120 nits. Put it another way, the contrast ratio between any two points after tone mapping should not exceed the contrast ratio without tone mapping.
Yes, I detect if the frame's peak luminance (after multiplying with 0.5) is within the display capabilities. If it is, I completely disable tone mapping and simply display the content as is. Any luminance modifications are only done if the frame's peak luminance exceeds the display's capabilities.
madshi is offline  
post #28676 of 31899 Old 02-02-2018, 06:40 AM
AVS Forum Special Member
 
Join Date: Dec 2014
Location: Mississauga, ON, Canada
Posts: 6,295
Mentioned: 118 Post(s)
Tagged: 0 Thread(s)
Quoted: 4371 Post(s)
Liked: 1608
Quote:
Originally Posted by madshi View Post
Yes, I detect if the frame's peak luminance (after multiplying with 0.5) is within the display capabilities. If it is, I completely disable tone mapping and simply display the content as is. Any luminance modifications are only done if the frame's peak luminance exceeds the display's capabilities.
I don't think this will work satisfactorily, unless I misunderstand what you're describing. Assuming the display's maximum luminance is 300 nits, and ignoring the multiplier:

- A frame containing 300 peak nits will be displayed as is;
- Another frame containing areas of 600 nits and 2000 nits peak, will be scaled down such that the peak become 300 nits or less (depending on the tone map), which means the 600 nits area will be displayed far dimmer than the other frame's 300 nits.
Dominic Chan is offline  
post #28677 of 31899 Old 02-02-2018, 07:48 AM
AVS Forum Special Member
 
madshi's Avatar
 
Join Date: May 2005
Posts: 7,571
Mentioned: 456 Post(s)
Tagged: 0 Thread(s)
Quoted: 2330 Post(s)
Liked: 2996
Quote:
Originally Posted by Dominic Chan View Post
I don't think this will work satisfactorily, unless I misunderstand what you're describing. Assuming the display's maximum luminance is 300 nits, and ignoring the multiplier:

- A frame containing 300 peak nits will be displayed as is;
- Another frame containing areas of 600 nits and 2000 nits peak, will be scaled down such that the peak become 300 nits or less (depending on the tone map), which means the 600 nits area will be displayed far dimmer than the other frame's 300 nits.
Well, considering that diffuse white is supposed to be about 100 nits, all we're talking about here is HDR specular highlights. It's not like large areas of the frame should have 600+ nits pixels. I'd expect there to be only few 600+ nits pixels which should be concentrated to small spots in the frame. Furthermore, the tone mapping compresses much stronger at the top than in the middle. So while in the 600 + 2000 nits frame, my algo would draw 600 nits pixels dimmer than in a max 600 nits frame, it should not be an extreme difference. Furthermore, the rolling average should prevent flickering if the 600 nits pixels stay constant and the 2000 nits pixels come and go.

The idea is that all pixels at or below diffuse white (which should really be the bulk of the frame's pixels) should stay the same regardless of the peak luminance of the frame, but if the frame's peak luminance differs, we can compress specular highlights more or less strongly to make the most out of the display's luminance capabilities.

If you think about it: If the whole movie has one sunlight scene with 4000 nits, but the rest of the movie is in the 600 nits range, do you really want the tone mapping to always reserve space for 4000 nits? That doesn't make too much sense in my book, and that's the whole reason why HDR10+ was created.
nathan_h and Manni01 like this.
madshi is offline  
post #28678 of 31899 Old 02-02-2018, 08:47 AM
AVS Forum Special Member
 
nathan_h's Avatar
 
Join Date: Mar 2001
Posts: 9,326
Mentioned: 43 Post(s)
Tagged: 0 Thread(s)
Quoted: 2724 Post(s)
Liked: 1955
Quote:
Originally Posted by madshi View Post

The idea is that all pixels at or below diffuse white (which should really be the bulk of the frame's pixels) should stay the same regardless of the peak luminance of the frame, but if the frame's peak luminance differs, we can compress specular highlights more or less strongly to make the most out of the display's luminance capabilities.

If you think about it: If the whole movie has one sunlight scene with 4000 nits, but the rest of the movie is in the 600 nits range, do you really want the tone mapping to always reserve space for 4000 nits? That doesn't make too much sense in my book, and that's the whole reason why HDR10+ was created.
BINGO, this appears to be what, for example, LG OLED displays were doing with HDR10 sources, dynamically preserving specular highlights while keeping the bulk of the image constant, and the results were excellent.

--

That said, people who have seen the Lumagen tone mapping, or even the Oppo, tend to rave about how it handles/retains low level shadow detail and color in low light scenes, which would seem to be something unrelated to dynamic tone mapping of specular highlights?
nathan_h is offline  
post #28679 of 31899 Old 02-02-2018, 08:49 AM
AVS Forum Special Member
 
madshi's Avatar
 
Join Date: May 2005
Posts: 7,571
Mentioned: 456 Post(s)
Tagged: 0 Thread(s)
Quoted: 2330 Post(s)
Liked: 2996
Quote:
Originally Posted by nathan_h View Post
That said, people who have seen the Lumagen tone mapping, or even the Oppo, tend to rave about how it handles/retains low level shadow detail and color in low light scenes, which would seem to be something unrelated to dynamic tone mapping of specular highlights?
Yes, that should be totally separate.
madshi is offline  
post #28680 of 31899 Old 02-02-2018, 09:29 AM
Senior Member
 
tibia's Avatar
 
Join Date: Sep 2001
Location: Portland, Oregon
Posts: 345
Mentioned: 1 Post(s)
Tagged: 0 Thread(s)
Quoted: 43 Post(s)
Liked: 38
x.v. color question

I use Chromapure AutoCal to calibrate my JVC RS600 with a Lumagen Radiance Pro and wonder if the color profile "x.v. Color" mentioned on page 31 in the RS600 Owner's Manual of any value now that UHD is common place? If UHD Bluray natively supports DCI-P3, could JVC RSxxx series projectors get closer to achieving 100% of the DCI-P3 gamut if the x.v. color profile were selected? Just curious if anyone has tried this.

Dennis
tibia is offline  
Sponsored Links
Advertisement
 
Reply Digital Hi-End Projectors - $3,000+ USD MSRP

Tags
jvc-rs500u synch/display issue? , RS600

Thread Tools
Show Printable Version Show Printable Version
Email this Page Email this Page


Forum Jump: 

Posting Rules  
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off