RetroTINK 5x-Pro

[Strider77]

What exactly is the SoG Thesh setting for on the Retrotink 5X?

[Tempest_2084]

I've mentioned this before, but I still haven't gotten a good answer. I'm looking for the correct term for the problem I'm having using older game systems (NES, SNES, Genesis) with my 5X Pro on my older LCD TV.

When I use older systems and play games that have darker colors on the 5X Pro (Metroid, Moonwalker, Ghouls and Ghosts, etc.) the screen will 'dim' as as everything scrolls and then goes back to normal brightness once the scrolling stops. This only seems to be notifiable on older systems (NES, SNES, Genesis, TG-16, SMS, etc.) and not on newer systems like PSX, Saturn, PS2, etc. I'm guessing what's happening is that my older LCD TV can't change the cells from dark to bright fast enough as the game scrolls and 'catches up' once the scrolling has stopped.

What is the name for this issue? Is it something with the refresh rate? I'm not seeing a ghosting image, it's just that some of the scanlines go dark (which makes the screen look dimmer). I'm also curious as to why newer systems don't seem to exhibit this issue (or if they do it's not noticeable).

[orange808]

I've mentioned this before, but I still haven't gotten a good answer. I'm looking for the correct term for the problem I'm having using older game systems (NES, SNES, Genesis) with my 5X Pro on my older LCD TV.

When I use older systems and play games that have darker colors on the 5X Pro (Metroid, Moonwalker, Ghouls and Ghosts, etc.) the screen will 'dim' as as everything scrolls and then goes back to normal brightness once the scrolling stops. This only seems to be notifiable on older systems (NES, SNES, Genesis, TG-16, SMS, etc.) and not on newer systems like PSX, Saturn, PS2, etc. I'm guessing what's happening is that my older LCD TV can't change the cells from dark to bright fast enough as the game scrolls and 'catches up' once the scrolling has stopped.

What is the name for this issue? Is it something with the refresh rate? I'm not seeing a ghosting image, it's just that some of the scanlines go dark (which makes the screen look dimmer). I'm also curious as to why newer systems don't seem to exhibit this issue (or if they do it's not noticeable).

Sounds like an accurate description of ghosting to me and you identified the cause. I imagine you don't notice it as much with newer systems because there are smaller "pixels" and more colors. Your eyes are less forgiving with chunky large objects and fewer colors, so you really see it on older machines. Same thing probably applies to the motion blur. It's also easier to see when there's a consistent pattern and very few colors in the background while scrolling.

For instance, Mega Man 2 drives me absolutely crazy on a bad display, because the scenery uses elaborate repeating tile patterns that seem to be drawn with "thin lines" and define their characteristics/details with bright colors accented by dark (often black) pixels. The really bright colors and black pixels seem to alternate side-by-side very often and it's torture for a slow LCD. Scrolling makes everything dark.

[Tempest_2084]

Sounds like an accurate description of ghosting to me and you identified the cause. I imagine you don't notice it as much with newer systems because there are smaller "pixels" and more colors. Your eyes are less forgiving with chunky large objects and fewer colors, so you really see it on older machines. Same thing probably applies to the motion blur. It's also easier to see when there's a consistent pattern and very few colors in the background while scrolling.

Oh ok so it is ghosting then. Good to know. Too bad there's nothing to be done except get a better TV.

[Guspaz]

VA panels have slower dark pixel response times than IPS or TN panels and suffer from this, and they're common in TVs due to their much better contrast ratios. Some modern VA panels (like the ones in Samsung's Odyssey G7/G9 displays) mostly solve this, but that's not true of all VA panels.

That said, you can still experience something somewhat similar under the right circumstances even with an OLED panel at 60 Hz, for example a thin vertical line on a black background. Then it's not because of the pixel response time (which with OLED is effectively instantaneous) but because of the motion blur caused by image persistence. That's from the way your eyes/brain works rather than a physical property of the display. In that case, you can use black frame insertion to combat it, which significantly reduces the perceived motion blur, albeit at the cost of overall brightness.

Once I started using BFI on my OLED for 60 Hz games, retro or modern, it was hard to go back...

[Tempest_2084]

Once I started using BFI on my OLED for 60 Hz games, retro or modern, it was hard to go back...

BFI?

[Guspaz]

Black Frame Insertion.

On an LG C1, with a 60 Hz signal, when enabled, it spends 50% of the time displaying the image and 50% of the time displaying black. It does this in a rolling pattern akin to a CRT. This reduces the image persistence which significantly reduces perceived motionblur.

Here you can see the before and after on an LG C1 with BFI enabled (attached).

No BFI at 60Hz:

Spoiler

With BFI at 60Hz:

Spoiler

The LG CX had an even shorter persistence window (less blur) but at a bigger cost to brightness.

[bobrocks95]

BFI downsides are a significant loss in brightness and if you're sensitive like I am, flicker. But you really can see it clean up motion on a fast moving game, like if I turn it on for Sonic 2 for example.

Until sample and hold dies it remains the best broadly available option though. You could also pick up an old plasma of course.

[Guspaz]

You can mitigate the brightness loss on the LG OLEDs by using ColorControl to force on/up the Peak Brightness setting while using BFI.

LG OLEDs are not sample and hold displays. They use a rolling refresh like a CRT. With or without BFI.

[fernan1234]

LG OLEDs are not sample and hold displays. They use a rolling refresh like a CRT. With or without BFI.

They are sample-and-hold. If they weren't they wouldn't need BFI.

Both OLED and "Crystal LED" technologies also have response times far shorter than LCD technology, and can reduce motion blur significantly. However, all consumer OLED Displays are sample-and-hold,[2][31] which leads to the same amount of motion blur as a traditional LCD Display.

https://en.wikipedia.org/wiki/Display_motion_blur

[Guspaz]

Fair enough. Point is that with a rolling refresh and BFI, the display pattern is pretty similar to a CRT, minus the fade, appearing pretty much the same to the human eye.

[bobrocks95]

Fair enough. Point is that with a rolling refresh and BFI, the display pattern is pretty similar to a CRT, minus the fade, appearing pretty much the same to the human eye.

A rolling scan would negate the need for BFI from what I understand. Probably would look nice and close to a CRT, but the only OLED displays I know of that use it are Sony PVMs.

[fernan1234]

Fair enough. Point is that with a rolling refresh and BFI, the display pattern is pretty similar to a CRT, minus the fade, appearing pretty much the same to the human eye.

The LG panels do not use a rolling refresh rate. They are sample-and-hold displays, meaning that each frame is shown and held in full for the duration of the refresh duty cycle (120Hz for the last few years). BFI can be a full black frame or a fraction of it being "rolled" down each held frame, which is what can reduce the persistence (or "eye-tracking") blur inherent to all sample-and-hold displays.

BTW, you may be interested in knowing that turning on BFI on LG OLEDs produces additional latency. The processing that handles the BFI is clearly not optimized.

A rolling scan would negate the need for BFI from what I understand. Probably would look nice and close to a CRT, but the only OLED displays I know of that use it are Sony PVMs.

And BVMs, but to be more precise those panels are also sample-and-hold, their drivers simply use a very good rolling scan BFI by default, and later software updates and models added the ability to turn it off with a "flicker free mode" setting.

The BFI implementation on these pro OLED monitors does have key advantages over the LG WOLEDs: 100% compensation for brightness loss, so picture is identical with "flicker" on or off, there is also no added processing latency for having it on, and its duty cycle is 60Hz which is perfect for 60fps content.

[Josh128]

The BFI on LC C class OLEDs is employed as the new frame image is alternated with a full screen black in a rolling pattern that rolls from top to bottom. Its not a sample-and-held image alternated with a sample-and-held black.

https://www.youtube.com/watch?v=DEAzEpAiWow

[fernan1234]

fernan, the BFI on LC C class OLEDs is employed as the new frame image is alternated with a full screen black in a rolling pattern that rolls from top to bottom. Its not a sample-and-held image alternated with a sample-and-held black.

I wonder if terms here are being used adequately. In any case, what's clear is that the display is sample-and-hold, and blacking out part of the frame in a rolling pattern does not change that, it simply helps our eyes to see less of the persistence blur. In other words, anything that the panel displays is technically "sample-and-hold", but certain patterns, like a flickering or rolling black frame-segment makes a difference at the level of our perception, but it doesn't change how the image is being displayed.

Again, LCDs and OLEDs are both sample-and-hold displays, that's how they work, how they paint a picture for us to see, in contrast to impulse displays like Plasma and CRT. All flicker (BFI) or strobing implementations are just a way for SAH displays to mimic the impulse behavior to some extent, purely for the benefit of our vision.

[Ed Oscuro]

Right, scan-and-hold doesn't mean the screen doesn't have the traditional scanout order. Normally the screen update pattern isn't too evident but recall that input latency testers show the top of a screen gets updated frame data faster than the bottom - that's just how the screen updates. For legacy compatibility, simplicity, and cost, displays typically should just update in the normal CRT-like rolling pattern. OLED has some flexibility about the actual timing compared to transmissive displays that have to coordinate a backlight with content updates; the real magic will be happening in the display processor.

[Josh128]

Of course, but the Sony Tri-master OLEDs are no different from the LG OLEDs in this regard-- they too, like all OLEDs, are sample and hold displays by nature.

[fernan1234]

Of course, but the Sony Tri-master OLEDs are no different from the LG OLEDs in this regard-- they too, like all OLEDs, are sample and hold displays by nature.

Yes, I said exactly that above, while pointing out that the rolling scan/BFI implementation on the former is superior thanks to the three factors I listed.

I really hope to see a similar implementation on consumer sets eventually, but I'm not holding my breath at this point, seeing how makers seem to care less and less about this. Even Sony's current flagship BVM doesn't have any kind of flicker at all. I suspect that consumer sets will focus on 120Hz and above for modern gaming since it has less disadvantages, but solutions for older 60fps and lower content will remain limited, and sadly that includes retro game content where it's most needed.

[Ed Oscuro]

Of course, but the Sony Tri-master OLEDs are no different from the LG OLEDs in this regard-- they too, like all OLEDs, are sample and hold displays by nature.

Yes. In the video you posted, both the left and right displays are scan-and-hold. The left one just shuts off the pixels to emulate a CRT. The right one is a transmissive LCD display and it shuts off the backlight.

What's notable with an emissive display is that if you can cycle the pixels faster than your target refresh rate you can use that extra refresh time to strobe the pixels on and off, like you see here. So some of this is down to the characteristics of the OLED technology (i.e., does it have enough brightness and endurance to hit the wanted brightness level while being off part of the time) and part is due to the display controller. Perhaps a frame buffer isn't needed at all for this kind of BFI.

@fernan, I think if display processor developers can figure out BFI with variable refresh rates then we will quickly see it adopted in consumer TVs. As it stands, even software-added BFI is very persnickety, so perhaps they're holding back because it is most in demand for gaming and yet modern console gaming is one of the hardest cases for BFI.

[Guspaz]

I really hope to see a similar implementation on consumer sets eventually

LG's OLEDs are certainly consumer sets, and do a rolling BFI in the same manner as the Sony OLED PVMs...

[fernan1234]

LG's OLEDs are certainly consumer sets, and do a rolling BFI in the same manner as the Sony OLED PVMs...

I was referring to the other advantages along with the rolling BFI: 1) brightness compensation, 2) no extra latency, 3) 60Hz duty cycle (older LG WOLEDs had it, but of course that also means a much darker picture).

In any case, now with the advent of relatively affordable QD-OLED, LG WOLEDs are not even worth thinking about. Now we should hope that new QD-OLED TVs and monitors will have good BFI implementations as well as compensation (the fact that QD-OLED panels can better sustain brightness than LG WOLED panels, especially in SDR, is already a good starting point).

[Ed Oscuro]

So that means people have done latency testing on OLED PVMs with BFI and old systems? How does it hold up with unstable framerate sources?

[fernan1234]

So that means people have done latency testing on OLED PVMs with BFI and old systems? How does it hold up with unstable framerate sources?

BTW it's also the OLED BVMs that have this not just the older PVMs.

I didn't have a Time Sleuth for exact figures, but I used the 240p test suite's display lag test with one of them next to a CRT getting the same signal (the OLED BVM via OSSC's HDMI output), and the difference with CRT was 1 frame consistently, with flicker on or off. 1 frame is pretty much as good as you can hope on a flat panel with a 1080p60 source. Content with unstable framerate will be displayed at 60Hz, with stutter like on a CRT, as well as any 60Hz flat panel without frame interpolation.

[Einzelherz]

All this display tech conversation made me wonder - what happened to the old "best TV" thread from a while ago? I think the title was something about Sony W series? I enjoyed reading that to keep up on screen tech since I'm still living in the early 2010s with my Plasma TVs.

[orange808]

Seems like we're repeating ourselves and arguing semantics, here.

Ham-fisted, barbaric, literal black frame insertion hasn't been a thing with panel display manufacturers for a long time. The "rolling" effect is assumed to be there. It helps with brightness and it reduces perceived flicker--and that's been understood for many years, now. I can't think of any recent single proper panel displays that are programmed by the manufacturer to simply insert completely black frames (in one single complete immediate binary change) and call it a day. Everyone has some form of "rolling" mechanism. Also, water is wet.

If you had a theoretical durable panel bright enough and the right software, rather or not it would be capable of displaying an entire image at one time becomes a choice--and terms like "sample and hold" versus "rolling raster scanout" become labels for specific display modes, not descriptions of the panel itself.

Semantics.

[fernan1234]

Sure, you can say that in one sense, but at the same time calling it all a rolling scanout is not the end of the story, as several crucial questions will remain open for current and upcoming panels. Even if we live in a better world with rolling BFI on all newer panels

1. What are the duty cycles supported? Are they user-adjustable, automatically set to match frame rate, or the same regardless of input frame rate?
2. Is there any frame doubling going on, for example, for 60fps content on 120Hz panels?
3. Does the panel support a single scanout per frame (i.e. single-strobing, especially at 60Hz)?
4. Does the panel adjust output to compensate for brightness loss induced by the rolling BFI, while also maintaining color accuracy? (note: LG WOLED panels literally cannot do this due the dependence on large white subpixels)
5. Is there an increase in latency from engaging the rolling BFI?

On actual non-sample-and-hold displays we don't need to even ask these questions because we're not dealing with a simulation of impulse display, all the answers are good as we had it by luck of the design with CRTs, and that's where we see real differences and not just semantics.

In practice this also matters because the trend seems to be going toward bad answers for those questions, except for #3 for now, and that trend is likely to get worse as TV and monitor manufacturers focus more on modern content, even if most of the above can be addressed with better software. But in this forum, and even just in this Retrotink topic, I assume most of us are interested in flat panels that can get us as close to a CRT-like experience as possible. Making a rolling BFI the new standard is a great step forward, but at the same time it's only catching up to something Sony did with pro panels over 10 years ago, and still leaves a lot of room for improvement to actually approach impulse display benefits to the point where panels being SAH stops being an issue for people into retro stuff.

[Guspaz]

1. They are rarely user-adjustable and are typically fixed, though some TVs may allow some minor amount of customization. But certainly not setting the duty cycle directly.

2. I'm not aware of any TV that does that with BFI. That said, with 30 FPS content on a 60 Hz output (as is common with game consoles), you're going to have a doubled image unless you also use motion interpolation to get that 30 Hz content to 60 or 120 Hz. Samsung reportedly has a very low latency gaming motion interpolation mode. I haven't tried it. LG's motion interpolation makes 30 Hz games look amazing with an extreme increase in motion clarity (when I tried it on the new 30 Hz Kirby game for Switch), but at the cost of a huge increase in lag (10ms -> 85ms). I'd be willing to put up with some additional lag on games like that, but not that much.

3. All TVs should support this. On the LG C1, you get 60Hz BFI and 120Hz BFI. You can tell it to use 120 Hz BFI on 60 Hz content, but of course this produces a doubled image, so you'd be best to use 60 Hz BFI. However, the C2 removed support for 120 Hz BFI entirely. This is unfortunate, though natively 120 Hz content has less need for BFI in the first place.

4. To some degree, they might (remember that even colour brightness can go higher in HDR than in SDR), but there is indeed a significant drop in maximum achievable brightness. You can force the "peak brightness" setting on with BFI using external third-party tools (it's locked in the TV's own interface) but this probably does hurt accuracy.

5. On older LG TVs there was around a half frame of added latency with BFI. On newer LG OLEDs I think that might be gone, however you can't use the TV's boost mode (reduce 60Hz latency) at the same time as BFI, so that's around 3ms of additional latency just from losing boost mode.

Ultimately all displays will be sample-and-hold going forward (and have been for many years), so the superiority of impulse displays is moot. CRTs are now expensive with even cheap consumer TVs starting to sell for hundreds of dollars. It's now all about getting the best out of sample-and-hold as we can.

I do agree that things seem to be on a somewhat negative trend. The LG CX had around a 20% image persistence for 60Hz content, and the LG C1 increased that to around 50%, reducing motion clarity in exchange for a much smaller hit in brightness. I think the tradeoff was strongly worth it (the difference in motion clarity appears to be minimal from UFO-like tests), but others disagree. The LG C2 removed support for 120 Hz BFI entirely. It's not clear if this is a temporary oversight or a new policy, but I'd tend to believe it's the latter. LG's C1 got a lot of praise for being almost ideal for retro content due to having things like BFI, low latency, and the ability to take almost any off-spec video timing/resolution you could throw at it. However, the C2 appears to have a whole bunch of issues that are problematic for retro content, like significant increases in latency when setting the aspect ratio to 4:3. Again, it's yet to be seen if this is just shitty launch firmware or not, but it's worrying.

[H6rdc0re]

I do agree that things seem to be on a somewhat negative trend. The LG CX had around a 20% image persistence for 60Hz content, and the LG C1 increased that to around 50%, reducing motion clarity in exchange for a much smaller hit in brightness. I think the tradeoff was strongly worth it (the difference in motion clarity appears to be minimal from UFO-like tests), but others disagree. The LG C2 removed support for 120 Hz BFI entirely. It's not clear if this is a temporary oversight or a new policy, but I'd tend to believe it's the latter. LG's C1 got a lot of praise for being almost ideal for retro content due to having things like BFI, low latency, and the ability to take almost any off-spec video timing/resolution you could throw at it. However, the C2 appears to have a whole bunch of issues that are problematic for retro content, like significant increases in latency when setting the aspect ratio to 4:3. Again, it's yet to be seen if this is just shitty launch firmware or not, but it's worrying.

What 20% image persistence are you talking about? Doing a head to head of a LG CX with BFI set to high and PVM L4 with all the scrolling tests of the 240p test suite yields perfect motion.

[fernan1234]

We use the word perfect a bit too lightly sometimes. The truth is that even the most ideal rolling BFI implementation literally cannot produce motion as clear as CRT for 60fps and below content (unless motion interpolation is also used, in which case the usual interpolation artifact problems are added to the mix).

It can definitely be good enough. On that matter, you guys should be paying attention to the new QD-OLED panels coming out, which by their design are much better positioned to use BFI while minimizing the disadvantages in a much better way than LG WOLED panels.

I'm sure there's a lot of people who "invested" in LG OLED TVs the past few years and don't want to make anyone feel bad about their purchase, but something 100% superior is available now and affordable at similar prices. I'd cut my losses and sell any LG OLED TV locally at a discount to buy a QD-OLED from Samsung or Sony.

[PearlJammzz]

We use the word perfect a bit too lightly sometimes. The truth is that even the most ideal rolling BFI implementation literally cannot produce motion as clear as CRT for 60fps and below content (unless motion interpolation is also used, in which case the usual interpolation artifact problems are added to the mix).

It can definitely be good enough. On that matter, you guys should be paying attention to the new QD-OLED panels coming out, which by their design are much better positioned to use BFI while minimizing the disadvantages in a much better way than LG WOLED panels.

I'm sure there's a lot of people who "invested" in LG OLED TVs the past few years and don't want to make anyone feel bad about their purchase, but something 100% superior is available now and affordable at similar prices. I'd cut my losses and sell any LG OLED TV locally at a discount to buy a QD-OLED from Samsung or Sony.

Samsung's new QD-OLED still has a lot to prove and Sony is great unless you like the gaming features. Samsung, traditionally, has been one of the single worst manufacturers when it comes to retro consoles or off-spec resolutions. The CX, and to a lesser degree, the C1 are mostly beloved for being OLED and supporting all sorts of weird, random video signals without fuss. Add in low input lag and the best BFI we've seen on a modern panel it's causing a lot of people to not really use their CRTs as much anymore. Add in the RT5X (and MiSTer) and its shadowmask support and the CRT-like experience is pretty awesome. Is it exactly like a CRT? No but some of that is in a good way. 65", sharper, perfect geometry, the wife loves it instead of hates it, etc. It's more of a 'good enough that I don't feel like I need to play on a CRT' instead of 'OMG! This is a perfect recreation of a CRT!!1!'

I don't see BFI as trying to replicate a CRT exactly. I see it as more of a potential solution to solve or at least minimize the shortcomings of sample and hold displays. Even OLEDs with their super fast pixel response times, like 10x faster than LED LCDs, has crappy motion resolution compared to a CRT. I don't think panel manufacturers are trying to recreate CRTs as much as just increase motion resolution and BFI does that (albeit with its own limitations). If anything I expected we'd see more investment into BFI especially as panels scale in frequency. What happens when we get 240hz OLED, or 480hz? Or even micro-LED, where will that stand as it'll still be sample and hold? This is always a moving target and this part of the thread likely won't age well as we move onto newer display techs in the coming years or get large advancements in OLED. There will always be some new hotness on the horizon but as someone who has been enjoying a CX for 2 years it's the best money I've ever spent on a display, ever. Zero regrets if the Samsung whoops its ass in every way (I hope it does!). All I care about is we take steps forward after (IMO) having so many years of steps backwards.