Software black frame insertion option on the MiSTer to get a motion blur free image

[Neocaron]

Hello there!

So I was wondering if a software based black frame insertion setting would be possible on the Mister? While it's available on select TVs to great effect and almost completely remove motion blur at just a small brightness cost, a software based solution would make it work on every LCD panel. Nothing should prevent this from being possible right? Is it feasible? Would the team be interested in doing it?

For people not familiar with it, here's a pretty old but detailed article explaining the whole process:
https://www.cnet.com/tech/home-entertai ... o-lcd-tvs/

[darksakul]

Not saying it's impossible, but you have to make the changes in each FPGA Core to support this.
The DE 10 Nano mostly runs on the FPGA Chip, the Arm processor side is mostly for file management/house keeping duties.

My Question is if this feature used on Low Level Software Emulation yet or not.

[H6rdc0re]

Even with BFI a LCD won’t have a completely blur free image. OLED however will be completely blur free with a 100% BFI cycle. Even older OLED displays. Brightness might suffer too much. You won’t be able to run both BFI and scanlines with ample brightness.

[Neocaron]

Even with BFI a LCD won’t have a completely blur free image. OLED however will be completely blur free with a 100% BFI cycle. Even older OLED displays. Brightness might suffer too much. You won’t be able to run both BFI and scanlines with ample brightness.

Yes you are right, but it will still look much better than it does now on LCD as well. The idea here would be to have the option.

And to answer the previews question, I haven't heard of black frame insertion on any emulator outhere. I feel like this is not broadly known for now and use only on the TV hardware side of things. I truly believe that the impact on retro gaming especially is massive as long as you have a decent amount of brightness on your screen in the first place. But basically you're saying this could not be applied as a general option? But only per core? It more complicated to do then, but still it would be awesome.

[hooxxx]

retroarch has a black frame insertion option that works on every core when activated

[Neocaron]

retroarch has a black frame insertion option that works on every core when activated

I had no idea!

[sonik]

For BFI to work the output has to be 120hz right?
There's some videos of mister outputting at 120hz (I have not tested it myself)
https://www.youtube.com/watch?v=vte-f1KKCg8

So it might be possible to handle the BFI at the framebuffer/scaler pass?

I do use the native BFI feature on my oled tv and it's amazing but it adds some latency.

[Neocaron]

For BFI to work the output has to be 120hz right?
There's some videos of mister outputting at 120hz (I have not tested it myself)
https://www.youtube.com/watch?v=vte-f1KKCg8

So it might be possible to handle the BFI at the framebuffer/scaler pass?

I do use the native BFI feature on my oled tv and it's amazing but it adds some latency.

Yeah since it's basically using the frametime between 60 and 120 to insert a blackframe right?
I don't know how it would work at a lower refresh rate...

[hooxxx]

I'm no expert but black frame insertion should double the Hz of orignal refresh rate so pal content (50Hz) should be 100Hz etc.
I wonder if universal option (like video filters) could be implemented in mister?

[SuperBabyHix]

I think even before you get to how to insert black frames you are going to run into a limitation with the Mister's HDMI output. I believe the pixel clock limit is somewhere around 180Mhz, I can't remember.
A 720p 120hz video mode is going to be around 160Mhz.
Using reduced blanking and a 4:3 screen mode would let you reduce that a bit, but I doubt you can get a much higher resolution than that.

[FoxbatStargazer]

I'd really like to see a closely related feature, an exact doubling of the core's refresh. This would be useful for reducing flicker on VGA CRTs, especially for PAL content. Kinda niche but there you have it. :p

I imagine these could both be new modes for vsync_adjust. Probably based on vsync_adjust=1 except that it doubles the core's refresh (and does black frames in one case). Bufferring is probably required to make this work so there would be a bit more lag compared to vsync_adjust=2.

I think there would also be demand for a locked 120hz version of BFI, in case of display incompatibility. Especially since it is important to keep the black frames consistently spaced, and not double up a black or image every so often. In that case it would be more like just doing the usual interpolation to 60 and put black frames between. In this case you would probably base on the video_mode's refresh rather than the core.

[Newsdee]

I'd really like to see a closely related feature, an exact doubling of the core's refresh

This is what this option does

forced_scandoubler=1

It makes it go from 15khz to 30khz

[FoxbatStargazer]

I meant vertical refresh, not horizontal. 50hz -> 100hz for example, doubling every frame.

[Anim8]

I believe the pixel clock limit is somewhere around 180Mhz, I can't remember.

Could the vblank be increased at 1080p@60hz? Increase to Quick Frame Transport(QFT).
https://forums.blurbusters.com/viewtopic.php?t=4064

I guess that leaves ~+30Mhz to work with? A larger vblank could reduce latency by forcing the scan-out to start sooner while also improving motion clarity when used with BFI. 30Mhz clock left to use I guess won't help much, all things considered.

While it's available on select TVs to great effect and almost completely remove motion blur at just a small brightness cost

I don't think its only limited to select TVs, as I'm using BFI on my monitor(I'm using a ViewSonic XG2431 for reference) but I can control the brightness by adjusting the Strobe Pulse Width setting, in ms. Longer flash-on duration increases brightness but reduces motion clarity.

The Strobe Pulse Width duration range that I can set is 0.1ms(~5nits screen brightness) to 4.0ms(~212nits screen brightness). 5nits is too dim and 212nits is too bright, so I tend use in the 2.0ms(no filters) to 3.0ms(with filters) range.

The downside to turning on BFI is it does cause the monitor to flicker like a CRT but the motion clarity becomes very clear.

[zimthuet]

I was wondering about the Viewsonic XG2431. How good is it really to use with a MiSTer and how bad is the flickering? The problem is I have no reference and I live in Europe (where the monitor isn't sold), so I'm thinking about importing one myself, but that's costly so any information on the performence you can give me is much appreciated.

Does the flicker cause eye strain? How bad is it to a let's say 60hz CRT PC-monitor?

[Anim8]

I was wondering about the Viewsonic XG2431. How good is it really to use with a MiSTer and how bad is the flickering? The problem is I have no reference and I live in Europe (where the monitor isn't sold), so I'm thinking about importing one myself, but that's costly so any information on the performence you can give me is much appreciated.

Does the flicker cause eye strain? How bad is it to a let's say 60hz CRT PC-monitor?

I would say the contrast ratio and the monitors OSD buttons are it's weak points. Also ignore the HDR marketing on it. Its not HDR at all, consider it as a SDR monitor. I would give the rtings and tftcenteal reviews a look as they cover it pretty well.
https://tftcentral.co.uk/reviews/viewsonic-xg2431
https://www.rtings.com/monitor/reviews/viewsonic/xg2431

I wouldn't call this monitor high end at all but in terms of game performance its motion clarity, input delay, response times etc. are about as good as I've seen on a IPS monitor or even vs TN monitors for that matter. CRT still wins out though. Paying a high price might make recommending it hard. Not many LED monitors support BFI at 60hz, which was one of the reason I picked this one. They sell them locally in Australia for around ₂₈₀ - 320 Euro(₄₅₀ - 490 AUD) including tax and shipping.

Flicker is hard to answer as it really depends on the person. If CRT flicker doesn't affect you at 60hz good chance your ok with this monitor but the light is still different. Its LED light so the wavelength output will likely be different IE LED tends to spike at _450nm(blue), _550nm(green), _650nm(red) with little in-between.

Also LED on/off is very square shaped where CRT starts as square but rolls off, so LED flicker might be a little harsher on the eyes in that regard. For me its been fine but if you read the blur busters thread some users there have noted getting headaches from it. I should note that I have always used bias lighting behind the screen which likely helps, plus it improves contrast.

wNYE1rx.jpeg (50.78 KiB) Viewed 2096 times

I only use strobe when playing games, otherwise I have it off. The BFI mode(pureXP) range supports 59hz - 240hz. The screen is 1080p and I have integer scaling on. This will often give a letterbox but that extra black space at the top/bottom also helps with better motion clarity without the need for a larger pixel clock.
See this image for why:

crosstalk-annotated-ANIMATED-VERTTOTAL.gif (253.39 KiB) Viewed 2097 times

To get really clear motion at 60hz(IE no crosstalk) you ideally want a high pixel clock such as 300 - 600Mhz but it still works fine with MiSter, as the monitor is multi-sync all the same. Around _9ms delay at 60hz, or _12ms delay with BFI on@60hz which is decent.
https://forums.blurbusters.com/viewtopic.php?t=8946

CRT is still the winner for MiSTer but for a gaming based IPS LED monitor it has worked well for me.

[zimthuet]

Thank you very much for the answer!