Thoughts on faux HDR on newer scalers and HDMI mods?

[BuckoA51]

PLEASE NOTE - Nothing I write here is to be taken as criticism of MakeMhz, RetroTINK or any other product!! These are amazing products I'm very happy with! Seriously, features like this are icing on a very delicious cake and if they don't work 100% the way I would have liked, that takes away NOTHING from how awesome they already are.

I was wondering if some of the more experienced and knowledgeable people have had chance to play with these HDR injection mods. At first I was nonplussed with them, I mean the HDR conversion Windows and Xbox does to old games is okay, but it goes wrong a lot too, completely crushing whites in some instances, and that system has access to the games assets as they're running on the console/computer, not just raw pixels as they are spat out by the console.

I played a little with the RetroTINK 5x version of this feature yesterday and it does produce a very bright, pleasing image. 240p test suite is definitely your friend for checking for clipping or over saturation of whites. Strangely, although my TV is set to full range, I could not get the RetroTINK 5x to not clip black unless I set it to limited RGB output, which seemed a little strange.

As for colour accuracy, what are peoples thoughts here? I don't like the idea of breaking colour accuracy just for a little bit more brightness but honestly the colours didn't seem to change too much. I lack the equipment to really calibrate the colours on either a CRT or a flat panel so I'm just having to go with values I find online for my TV but the reds on my CRT look a lot more crimson than on the HDTV although the HDTV should be closer to accurate based on the various sources I've read online.

Finally, dynamic tone mapping. You'd think this would need to be off, and yet I seemed to get better results with it on.

Burn in is a worry using these modes too. On my OLED (LG C9) I have disabled power saving but not gone to the lengths of disabling dimming in the service menu entirely, which means playing games with static content like health bars (well, those aren't so static with my low performance play, but you get the idea) will cause the TV to dim down over time... so I wonder again if this is just going to start out bright and end up just the same brightness as with the HDR injection off.

Anyway, I welcome everyone's thoughts on this. Is it the next great thing in retro console upscaling or a gimmick that videophiles and those of us concerned with accuracy should turn off?

[fernan1234]

It's an amazing development in the retro scene, absolutely.

Is it perfect? No, but it's a huge step toward replacing CRTs. Arguably the best added feature the 5X has had to date.

A lot of the issues you refer to depend on the TV, how it handles full vs limited, tone mapping algo, native color gamut, and calibration. And also in particular to using OLED with the concern of burn in, plus they don't get nearly as bright in HDR as other displays. I'd say that in spite of their disadvantages, a good miniLED with tons of dimming zones and/or a good dimming zone algo is a great pairing with a Tink5X's HDR flagging. I was able to get a sense of the true potential when hooking it up to a miniLED display that can do 1000nits full screen and 1600nits peak. No commercial OLED can get even close to that, and probably never will. And of course microLED in the future will be an even better solution.

[Guspaz]

I think the problem is that you're completely missing the point of these HDR modes. They're meant purely to compensate for the brightness loss inherent with scanlines/CRT masks/BFI/etc. They are not meant to provide an HDR experience like Microsoft's AutoHDR features do. They will (and should) make your image look worse if you just enable them in isolation rather than trying to use them to compensate for other perceived brightness loss.

[BuckoA51]

I think the problem is that you're completely missing the point of these HDR modes. They're meant purely to compensate for the brightness loss inherent with scanlines/CRT masks/BFI/etc. They are not meant to provide an HDR experience like Microsoft's AutoHDR features do. They will (and should) make your image look worse if you just enable them in isolation rather than trying to use them to compensate for other perceived brightness loss.

No that's exactly what I expect them to do, please understand I'm not expecting miracles here. However (as with AutoHDR) I'm concerned of side effects to picture accuracy hence me asking peoples opinions.

[Konsolkongen]

I think the problem is that you're completely missing the point of these HDR modes. They're meant purely to compensate for the brightness loss inherent with scanlines/CRT masks/BFI/etc. They are not meant to provide an HDR experience like Microsoft's AutoHDR features do. They will (and should) make your image look worse if you just enable them in isolation rather than trying to use them to compensate for other perceived brightness loss.

No that's exactly what I expect them to do, please understand I'm not expecting miracles here. However (as with AutoHDR) I'm concerned of side effects to picture accuracy hence me asking peoples opinions.

I think that comes down to how well Mikechi has managed to do colorspace conversion to rec2020. If done right I don't think it would harm picture accuracy, but I think your TV has to support HGiG (or similar method of hardclipping HDR), and the RetroTINK probably needs an option to set max luminance accordingly, otherwise I think the TV will do tonemapping which could impact the luminance curve negatively.

[bobrocks95]

Finally, dynamic tone mapping. You'd think this would need to be off, and yet I seemed to get better results with it on.

Like Konsolkongen said, you probably want to try the HGIG mode that actually disables tone mapping. I have a B9 and the tone mapping setting is misleading- On is dynamic tone mapping, Off is static tone mapping, and HGIG is tone mapping off.

That said, it's meant to be used with games that let you set your peak luminance so the game can essentially handle its own tone mapping, so ideally the RetroTink adds something like this in the future. HGIG might end up looking worse despite being more accurate (Tink could be outputting a peak brightness way too high for the display and clipping a lot on the high end).

A lot of the issues you refer to depend on the TV, how it handles full vs limited, tone mapping algo, native color gamut, and calibration. And also in particular to using OLED with the concern of burn in, plus they don't get nearly as bright in HDR as other displays. I'd say that in spite of their disadvantages, a good miniLED with tons of dimming zones and/or a good dimming zone algo is a great pairing with a Tink5X's HDR flagging. I was able to get a sense of the true potential when hooking it up to a miniLED display that can do 1000nits full screen and 1600nits peak. No commercial OLED can get even close to that, and probably never will. And of course microLED in the future will be an even better solution.

People are always complaining about OLED brightness numbers and saying they suck... I dunno it's plenty bright in the room I have it in, highlights in HDR can be retina-searing for me. When I buy a PC monitor the first thing I do out of the box is crank the brightness down because they are way too damn bright. I do not want a 1000 nit fully white screen acting like a searchlight shining on me, ~800 nit highlights are plenty (and Samsung's new OLED panels already hit 1000 nit highlights in their first generation).

[fernan1234]

People are always complaining about OLED brightness numbers and saying they suck... I dunno it's plenty bright in the room I have it in, highlights in HDR can be retina-searing for me. When I buy a PC monitor the first thing I do out of the box is crank the brightness down because they are way too damn bright. I do not want a 1000 nit fully white screen acting like a searchlight shining on me, ~800 nit highlights are plenty (and Samsung's new OLED panels already hit 1000 nit highlights in their first generation).

Those highlights feel retina-searing because, as you should with OLED, you're watching in a very dark room. Normal sun light when you go outside is way brighter and your eyes are fine

But anyway, even if OLED screens are getting brighter, people will probably have a lot of concern about burn in, especially when you're using these "faux" HDR modes when their real usefulness is precisely for retro games with scanline or mask filters enabled for CRT simulation, which means you'll have every other "scanline" being a bright HDR picture while the rest are blank, on a 4:3 picture displayed on your 16:9 OLED...

Personally I wouldn't be too worried especially with a QD-OLED panel that seems much more resistant to burn in, and I wouldn't buy a TV now expecting to use it for more than 3-4 years anyway. But again I'm sure many will be concerned and avoid this use-case on OLEDs entirely.

[BuckoA51]

I played using the DCDigital 2 with the HDR stuff on and it was looking great. Very vibrant picture with VGA style scanlines. It looked brighter than the CRT I had hooked up using the consoles analogue output. Overall it made for a very pleasing experience, sadly my TV doesn't support the 1440p the DCDigital 2 can output, so I couldn't try that, but even at 960p it was looking pretty nice and honestly it was hard to pick a favourite between the OLED and the CRT, though I think the OLED was stretching the images aspect ratio a tad (I should probably check in 240p suite...)

HGIG might end up looking worse despite being more accurate (Tink could be outputting a peak brightness way too high for the display and clipping a lot on the high end).

That certainly seemed the case, HGIG produced a very dark image compared to tone mapping on or off.

I thought for HGIG to work both source and target display needed to support them and I don't see mention of HGIG in RT5x or DCDigital. HGIG is supposed to follow the calibration you set in the consoles HDR settings (I'm probably understanding this wrong though).

Is there some metadata in HGIG signals to tell the TV how to tone map, or is it just about agreeing minimum/maximum values?

[Konsolkongen]

That certainly seemed the case, HGIG produced a very dark image compared to tone mapping on or off.

I thought for HGIG to work both source and target display needed to support them and I don't see mention of HGIG in RT5x or DCDigital. HGIG is supposed to follow the calibration you set in the consoles HDR settings (I'm probably understanding this wrong though).

I think you are understanding HGiG correctly. On the most common LG OLED TVs I believe HGiG hard clips HDR to 800 nits. The RetroTink should ideally have an option to match this value for a true 1:1 linear brightness scale.

[SuperSpongo]

User Grave from circuit-board.de has done some extensive tests with the Retrotink implementation. Have a look:
https://circuit-board.de/forum/index.ph ... /?pageNo=2

[BuckoA51]

That really is an in-depth analysis, thanks for that. It does seem as I feared, engaging these modes does come at the cost of colour accuracy and care must be taken not to clip detail through excessive brightness.

That said, for video games where one /could/ argue colour accuracy isn't that important (it's not like video games back then were made with the care and calibration movies were) it sill looks pretty nice.

For sure at minimum you want to test your settings against a grey ramp in something like 240p suite to make sure you're not clipping detail in blacks or whites.

[SuperSpongo]

It also seems like MiSTer has a much more sophisticated implementation by now:
https://misterfpga.org/viewtopic.php?t=5928&start=120

[bobrocks95]

That certainly seemed the case, HGIG produced a very dark image compared to tone mapping on or off.

I thought for HGIG to work both source and target display needed to support them and I don't see mention of HGIG in RT5x or DCDigital. HGIG is supposed to follow the calibration you set in the consoles HDR settings (I'm probably understanding this wrong though).

I think you are understanding HGiG correctly. On the most common LG OLED TVs I believe HGiG hard clips HDR to 800 nits. The RetroTink should ideally have an option to match this value for a true 1:1 linear brightness scale.

Pretty much correct, though HGIG isn't really a thing that has to be explicitly supported, it just expects your source to do its own tone mapping. From the detailed write-up that was posted, the RT5X isn't doing anything past flagging the output as HDR. So it may not be able to support any peak brightness settings. HGIG should look really dark because it's just passing through the 0-100 nit range from the SDR source, if I'm understanding correctly. Dynamic tone mapping will punch that all up, which is why it's prone to crushing blacks.

And at least for PS4 generation, HDR being so new meant most games ignored the console's calibration and just went by their own internal tool of wildly varying quality.

[Konsolkongen]

And at least for PS4 generation, HDR being so knew meant most games ignored the console's calibration and just went by their own internal tool of wildly varying quality.

Many new PS5 games do this too. But at least most games have ingame adjustments if they don't support HGiG from the consoles settings. It isn't ideal, but at least you only have to enable tone mapping with the few games that don't offer any adjustments at all

[Guspaz]

The RT5X does support some basic colour correction for HDR output to try to keep the colours looking reasonable (added in v2.76), but as I understand it full colour correction could only be done on something like the RT4K.

My LG C1's brightness is perfectly fine in the vast majority of cases, but then sometimes it isn't. Enabling BFI on SDR content is one such example. I was playing Metroid Prime Remastered on it and I wanted to turn on BFI for more motion clarity. Which it provided, but then the image dimmed below where I'd like it. I used ColorControl to force the TV to enable peak brightness high, and that helped, though it's still not bright enough and has some other side effects. Just because HDR highlights on an OLED are bright enough, or just because normal SDR viewing is bright enough, doesn't mean the TV is bright enough for all scenarios.

As for burn-in concerns, I don't think we've ever seen anybody report 4:3 or scanline simulation burn-in on an OLED TV. Even people like Try4ce who made extremely heavy use of their LG OLED for 4:3 content reported no 4:3 burn-in after years. In fact when he replaced that TV, it was because of a sort of splotchy/noisy burn-in pattern that was evenly distributed across the screen, and there was still no hint of 4:3 burn-in even in contrast-enhanced photos.

[BuckoA51]

I notice PixelFX have the ability to upload custom gamma tables to their newer mods, this could presumably correct the colours perfectly, if we could figure out the correct values to upload.