shmups.system11.org

Shmups Forum
 
* FAQ    * Search
 * Register  * Login 
It is currently Mon Feb 17, 2020 3:29 pm View unanswered posts
View active topics



Post new topic Reply to topic  [ 81 posts ]  Go to page 1, 2, 3  Next
Author Message
 Post subject: 31KHz CRT: 240p120 vs. 240p120 w/BFI vs. 480p60 w/ Scanlines
PostPosted: Thu Feb 06, 2020 3:50 am 


User avatar

Joined: 16 Jan 2014
Posts: 734
On the OSSC Pro thread there was some discussion about true 240p120 on a 31KHz CRT monitor and its advantages and disadvantages vs 480p60 with artificial scanlines. There was also some discussion about how distracting/noticable the double strobing effect is when running 60fps content on a 120Hz refresh rate monitor, whether or not black frame insertion (BFI) would alleviate the strobing effect, and how both compare to the same content displayed at 480p60 with full artificial scanlines inserted.

After much tinkering around and testing, I came to the following conclusions:

1.) Double Strobing Illusion: It is indeed visible on CRT when displaying 60fps animation at a 120Hz screen refresh. It is pretty subtle on most content, I didnt even notice it at first until I looked for it. Its most noticeable on fast moving sprites or backgrounds, and almost completely unnoticeable on slower animation. Its one of those things where once you see it, you cant "unsee" it, but the illusion (and I use that word on purpose, because it is indeed an illusion and is not able to be captured by video or photograph) , in my opinion is subtle enough even on fast moving content to not make it a dealbreaker. Opinions will vary on that, of course.

2.) Black Frame Insertion on 60fps 120Hz Content: When objections arose concerning the double strobing effect, I argued that black frame insertion could be used, as an alternative to motion interpolation, to alleviate the double strobing effect. Some folks disagreed that BFI would work on a CRT like it does with LCD or OLED.
Xer Xian wrote:
The double-image effect of repeated frames on a CRT cannot be alleviated with BFI.

After training myself to easily recognize the effect in specific areas of certain games, I used the BFI feature in Retroarch and carefully observed those same areas again in those same games and I can say with 100% confidence that the BFI completely eliminates the double strobing illusion. This comes at the cost of significant brightness loss vs the non-BFI 240p120 mode.

3.)480p60 with Full Artificial Scanlines: The question arose-
Xer Xian wrote:
I think the question here is what's wrong with line-doubling 240p and adding full-intensity fake scanlines?

Fair enough, seems like an honest question and to be frank, I hadnt thought to compare it at that point. So, I did some in depth comparisons of 480p60 with full artificial scanlines vs true 240p120 and made several observations. First, at least on CRT, the true 240p120 mode is significantly brighter than 480p with scanlines. This manifests itself, as it was also discussed, in the appearance of thinner, more natural looking (in my opinion) scanlines than the 480p60 + artificial scanlines mode. So indeed there is a significant visual difference between the two modes, at least on CRT.

4.)240p120 w/ BFI vs 480p with Full Artificial Scanlines: So during the course of testing all these modes, I made an interesting observation-- 240p120 w/BFI and 480p with full artificial scanlines are virtually identical. In overall brightness, they appear to my eye as identical to each other. In terms of scanline thickness, again, identical. Per Fudohs comments in the OSSC Pro thread, and my own previous experiences with 480p modes, I was not expecting this, but I can not detect a noticeable difference. Finally, in terms of the double strobe illusion, it is completely absent from both modes.

In conclusion, I still stand by my original stance that a 240p120 mode is worth implementing on the new OSSC. It is far brighter and has more natural looking scanlines than the alternatives. After comparing 240p120 BFI and line doubled 480p with full scanlines on CRT, it would be tempting to say that a 240p120 BFI mode would not be worth the trouble to implement as its indistinguishable from line doubled 480p w/ full scanlines, BUT-- I believe that the 240p120 BFI mode would be merited on 120Hz LCDs, where it would not only alleviate the double strobing illusion, but also greatly reduce blurring that is prevalent on 60Hz content on LCD screens.

Finally, I took some photographs of each mode and carefully stitched them together. I used a shutter speed of 1/20 sec with an ISO of 1600 for each shot, and shot them from the identical location on a tripod. I was very pleased with how they came out as they represent the differences when viewed live very closely, even if the 240p120 default mode is a bit overexposed. The differences you see here are very , very close to the differences you see in person.

Full Size: https://i.imgur.com/RAvJmYV.jpg
Image


Top
 Offline Profile  
 
 Post subject: Re: 31KHz CRT: 240p120 vs. 240p120 w/BFI vs. 480p60 w/ Scanl
PostPosted: Thu Feb 06, 2020 6:14 am 



Joined: 11 Dec 2014
Posts: 360
Some good points.
If you want some interactive comparisons you should use https://imgsli.com
I think people can get a better idea of the differences of an A/B comparison when they can interactively switch parts of the image as they see fit.


Top
 Offline Profile  
 
 Post subject: Re: 31KHz CRT: 240p120 vs. 240p120 w/BFI vs. 480p60 w/ Scanl
PostPosted: Thu Feb 06, 2020 12:01 pm 


User avatar

Joined: 16 Jan 2014
Posts: 734
BONKERS wrote:
Some good points.
If you want some interactive comparisons you should use https://imgsli.com
I think people can get a better idea of the differences of an A/B comparison when they can interactively switch parts of the image as they see fit.


Good idea, I'll look into it.


Top
 Offline Profile  
 
 Post subject: Re: 31KHz CRT: 240p120 vs. 240p120 w/BFI vs. 480p60 w/ Scanl
PostPosted: Thu Feb 06, 2020 2:25 pm 



Joined: 14 Aug 2017
Posts: 787
The problem with software-based/external BFI is that it's vulnerable to CPU performance dips. So when Retroarch is doing the BFI for you and at any point your PC has a hiccup you will see it, usually as a missing frame, jitter, or some other artifact. Of course no CRT has its own BFI, as it never needed it, so on CRTs you'd need an externally generated BFI subject to this limitation.

I think 240p120 would be the only "usable" option (given other, better options are available), though only for games with little to no motion. RPGs, adventure games, etc. Ironically for this site, definitely not good for shmups and such. Anyway this should be easy to implement on the OSSC Pro so I imagine it'll be available.


Top
 Offline Profile  
 
 Post subject: Re: 31KHz CRT: 240p120 vs. 240p120 w/BFI vs. 480p60 w/ Scanl
PostPosted: Thu Feb 06, 2020 3:00 pm 


User avatar

Joined: 16 Jan 2014
Posts: 734
fernan1234 wrote:
The problem with software-based/external BFI is that it's vulnerable to CPU performance dips. So when Retroarch is doing the BFI for you and at any point your PC has a hiccup you will see it, usually as a missing frame, jitter, or some other artifact. Of course no CRT has its own BFI, as it never needed it, so on CRTs you'd need an externally generated BFI subject to this limitation.

I think 240p120 would be the only "usable" option (given other, better options are available), though only for games with little to no motion. RPGs, adventure games, etc. Ironically for this site, definitely not good for shmups and such. Anyway this should be easy to implement on the OSSC Pro so I imagine it'll be available.


I honestly dont think it would be limited to games with limited to no motion though. Even action games like Ghouls N Ghosts dont exhibit much of it at all. Honestly. Granted, its not the highest speed game in the world, but still, it is a bonafide action game. About the only place you can see it is if you throw a lance across the screen and pause the game, in the center of the lance there is a colored jewel or pixel. In motion in 240p120, that jewel becomes invisible due to the slight manifestation of the effect on that lance, but I had to look closely to see that. Its actually no worse than the motion blur that occurs on my 75Hz IPS LCD (running at 60Hz for this content, of course) screen. The jewel also disappears on the lance on the LCD and when you pause it, you can see it again. On LCD it disappears due to the blur, whereas on CRT its due to the double strobe effect.

Even in games like SMW, the effect is virtually unnoticeable except when running at full speed and looking at small textures in the foreground, such as rocks. As far as jumping and kicking turtleshells, etc, its no problem.

In any case, as far as BFI is concerned, using RA was only for testing. While I dont know for sure technically, I am pretty positive that if the new OSSC can frame double 240p60 content, it should be a trivial matter to have the doubled frame consist of pure black, or any solid color really. Also, Marqs mentioned motion interpolation could also be accomplished at the cost of a bit more latency. If its only a single frame or so, this could very well be a viable option as it could be used to retain full brightness while at the same time negating the double strobe illusion.


Top
 Offline Profile  
 
 Post subject: Re: 31KHz CRT: 240p120 vs. 240p120 w/BFI vs. 480p60 w/ Scanl
PostPosted: Thu Feb 06, 2020 4:34 pm 


User avatar

Joined: 20 Aug 2016
Posts: 1477
Super Mario World is a good choice for still photos to demonstrate scanlines, but you don't want to use it as a test pattern for motion.

If you look closely, the scrolling isn't smooth in SMW. Try out a water level and see. Those hitches aren't your display. It's the game.

For scrolling motion clarity testing, NES Super Mario Bros might be a better choice for horizontal motion. For vertical motion, Zanac is a good test; although you might consider a Game Genie code so you can focus on the backround. Persistence blur is particularly evident on the NES.

If you're using a capture card, Rygar and SMB2 are good at exposing scaling problems--although the 240p Test Suite can accomplish the same task.
_________________
We apologize for the inconvenience


Top
 Offline Profile  
 
 Post subject: Re: 31KHz CRT: 240p120 vs. 240p120 w/BFI vs. 480p60 w/ Scanl
PostPosted: Thu Feb 06, 2020 4:36 pm 


User avatar

Joined: 06 Feb 2005
Posts: 833
Location: Italy
You went through a lot of trouble to test this, so thanks for reporting back. Still, your results should be quite obvious to anyone with a little familiarity of CRT displays and the quirks of human vision and what causes them.

Some facts:

- The resolution and frame rate of the source signal and the refresh rate any given CRT is running at have no bearing on scanlines/blanklines width. 240p120 scanlines (blanklines) are not more natural-looking than fake ones done well

- A CRT displaying 240p120 will look brighter than when displaying 480p60 with 100% scanlines due to the increased refresh rate and the fixed decay time of the phosphors (active lines are drawn faster, so more phosphors stay lit per unit of time). The trade-off of that is the double-image effect (and a handful of milliseconds of lag)

- The double-image effect of repeated frames on a CRT cannot be alleviated with BFI. If you are no longer seeing the effect then RA must be running BFI at 60hz instead of 120hz (total frame rate being 120hz instead of 240hz) and substituting the repeated frame with a black frame, thus losing information (even if redundant). But then the added brightness is lost and you're left with something that is indistinguishable from 480p with 100% scanlines while needlessly complicating things. Again:

Quote:
The fade to black is the exact reason why the effect is present on CRTs (and why it is absent on sample&hold display). If you feed 240p120 to a modern display and activate 120hz BFI you will substitute one kind of vision artifact (image persistence) with another (double-image effect).


And to be clear, I was not trying to bring down your proposal to implement frame doubling on the OSSC Pro. I was just interested in bringing some facts to the discussion.


Last edited by Xer Xian on Thu Feb 06, 2020 4:38 pm, edited 1 time in total.

Top
 Offline Profile  
 
 Post subject: Re: 31KHz CRT: 240p120 vs. 240p120 w/BFI vs. 480p60 w/ Scanl
PostPosted: Thu Feb 06, 2020 4:38 pm 


User avatar

Joined: 20 Jul 2017
Posts: 481
Are these CRTs able to accept Line3x from the OSSC? I feel like Line3x with 100% scanlines would probably also achieve the look you want.


Top
 Offline Profile  
 
 Post subject: Re: 31KHz CRT: 240p120 vs. 240p120 w/BFI vs. 480p60 w/ Scanl
PostPosted: Thu Feb 06, 2020 4:49 pm 


User avatar

Joined: 16 Jan 2014
Posts: 734
orange808 wrote:
Super Mario World is a good choice for still photos to demonstrate scanlines, but you don't want to use it as a test pattern for motion.

If you look closely, the scrolling isn't smooth in SMW. Try out a water level and see. Those hitches aren't your display. It's the game.


You are correct at walking speed and swimming speed, however at full running speed, the scrolling of the foreground at least, is perfectly smooth. It is also at this speed where the illusion can be seen on the small rock textures in the ground.


Top
 Offline Profile  
 
 Post subject: Re: 31KHz CRT: 240p120 vs. 240p120 w/BFI vs. 480p60 w/ Scanl
PostPosted: Thu Feb 06, 2020 5:35 pm 


User avatar

Joined: 16 Jan 2014
Posts: 734
Xer Xian wrote:
- The resolution and frame rate of the source signal and the refresh rate any given CRT is running at have no bearing on scanlines/blanklines width. 240p120 scanlines (blanklines) are not more natural-looking than fake ones done well.


This is incorrect (and I can prove it with closeup photography). The reason why is that at increased brightness on CRT, the thickness of the blank lines decreases. There is no technical way for line doubled 240p at 480p60 to match the brightness of 240p120, and this is the exact reason that the blanklines on the 240p120 content are a bit thinner than the 480p60 with blank line insertion. Sure, if I lower the brightness and contrast on the monitor to match the luminance of the 480p content, the blanklines will appear identical--however, that has no bearing on the fact that the additional luminance (only achievable in the 120Hz mode)does in fact reduce the visible scanline thickness. As far as the scanlines being more natural looking, that is a matter of opinion-- but if your measuring stick for "natural looking" is the thickness of the lines visible on a highly luminous FD Trinitron, then I think that most would agree the 240p120 blank lines are more natural looking.


Xer Xian wrote:
- A CRT displaying 240p120 will look brighter than when displaying 480p60 with 100% scanlines due to the increased refresh rate and the fixed decay time of the phosphors (active lines are drawn faster, so more phosphors stay lit per unit of time). The trade-off of that is the double-image effect (and a handful of milliseconds of lag)


Agree.

Xer Xian wrote:
- The double-image effect of repeated frames on a CRT cannot be alleviated with BFI. If you are no longer seeing the effect then RA must be running BFI at 60hz instead of 120hz (total frame rate being 120hz instead of 240hz) and substituting the repeated frame with a black frame, thus losing information (even if redundant). But then the added brightness is lost and you're left with something that is indistinguishable from 480p with 100% scanlines while needlessly complicating things.

You are incorrect here. It not only can, but it does, and this I can say with 100% certainty. This is 240p120 Hz with BFI, not 240p240 with BFI. I never said anything about 240Hz refresh anywhere in my posts. 240p120 with BFI = 1 image frame every 1/120 sec followed by 1 black frame every 1/120 sec. The end result is indeed indistinguishable from 480p with 100% scanlines, and I said as much above.



Xer Xian wrote:
If you feed 240p120 to a modern display and activate 120hz BFI you will substitute one kind of vision artifact (image persistence) with another (double-image effect).


I disagree here. If you were to do 240p120 w/BFI on a 120Hz LCD, what you are really achieving is eliminating motion blur that will be present on the same content at 60Hz. You will not be introducing
a CRT-like double strobing effect to moving objects and why would you? You are still inserting a black frame in between every game and/or flickering the backlight to eliminate or reduce the visibility of the second 120Hz frame. Its simply going to result in blur reduction. By your argument here, you are in effect saying that all blur reduction by BFI in sample and hold displays is going to result in a strobing effect of animation. Is that what you are saying? Without a doubt, BFI done in this way will differ from a hardware backlight strobing and is sometimes used as interchangeable terminology, but BFI was introduced as a method of controlling motion blur on sample and hold displays, for sure.

Xer Xian wrote:
And to be clear, I was not trying to bring down your proposal to implement frame doubling on the OSSC Pro. I was just interested in bringing some facts to the discussion.


Understood, I welcome facts and debate of such. If I am wrong about something, I will 100% admit it and welcome any facts that prove otherwise.


Top
 Offline Profile  
 
 Post subject: Re: 31KHz CRT: 240p120 vs. 240p120 w/BFI vs. 480p60 w/ Scanl
PostPosted: Thu Feb 06, 2020 6:47 pm 


User avatar

Joined: 06 Mar 2006
Posts: 11998
Location: Germany
Quote:
The resolution and frame rate of the source signal and the refresh rate any given CRT is running at have no bearing on scanlines/blanklines width.

that's wrong indeed - as Josh already mentioned. After all remember why linedoublers/quadruplers were introduced in the first place: to reduce the visible scanlines (as in the "dark lines between") and increase the light efficiency on CRT projectors.

I'm not all suprised by the difference scanline width betweeen 240p120 and 480p60 with artificial scanlines. That's exactly what I mentioned in the other thread. I AM surprised though that the 240p120/BFI shots make the scanlines look as strong as they do. I would have expected the BFI ones to range right between the 240p120 and 480p60 ones.


Top
 Offline Profile  
 
 Post subject: Re: 31KHz CRT: 240p120 vs. 240p120 w/BFI vs. 480p60 w/ Scanl
PostPosted: Thu Feb 06, 2020 6:56 pm 


User avatar

Joined: 06 Feb 2005
Posts: 833
Location: Italy
Look you guys, I am willing to concede that the perceived width of the blanklines might be a tiny bit smaller as a result of the increased brightness (which is a perceptual, subjective attribute - as opposed to luminance, which is a measurable quantity). The actual scanlines and blanklines width must be the same whether the CRT is displaying 240p120 or 480p60 with fake scanlines.

Quote:
240p120 with BFI = 1 image frame every 1/120 sec followed by 1 black frame every 1/120 sec.


Then your CRT is not displaying repeated frames. BFI on a CRT does not improve motion in any (direct) way. It only improves it in this specific case because it alters the source signal by removing the frames that cause the effect in the first place. That's not how BFI is supposed to work. This should also answer your question on 240p120 w/ BFI on LCDs. Proper BFI of a 120hz signal requires a refresh rate of 240hz to work. If your source outputs 240p120 and your LCD does proper 120hz BFI then it is essentially (badly) mimicking a CRT and you'll end up with the same double-image effect (plus whatever blur is inherent in the specific LCD panel and the residual persistence of vision). If your LCD does 60hz BFI and refreshes at 120hz then it must discard half the frames and what is the point of feeding it frame doubled 240p in the first place then?


Top
 Offline Profile  
 
 Post subject: Re: 31KHz CRT: 240p120 vs. 240p120 w/BFI vs. 480p60 w/ Scanl
PostPosted: Thu Feb 06, 2020 7:47 pm 



Joined: 14 Aug 2017
Posts: 787
Originally the point of 240p120 was to get a 240p input into those PC monitors that otherwise would not be able to display a 240p60 signal (i.e. 15khz), and BFI was used with this approach precisely to discard the doubled frames, ending up with the original 60 frames per second. Of course this all assumes an idealized model where the system/game outputs a consistent frame rate, and there are no performance dips on the software side.


Top
 Offline Profile  
 
 Post subject: Re: 31KHz CRT: 240p120 vs. 240p120 w/BFI vs. 480p60 w/ Scanl
PostPosted: Thu Feb 06, 2020 7:55 pm 


User avatar

Joined: 06 Mar 2006
Posts: 11998
Location: Germany
Quote:
The actual scanlines and blanklines width must be the same whether the CRT is displaying 240p120 or 480p60 with fake scanlines.

Why are you assuming this? I argued this before. They're not. If you compare a 240p120 image to a 480p60 image WITHOUT artificial scanlines, you can see that the 480p image still got scanlines. 480 of them to be exact and quite thin ones. These add to the perceived thickness of the artificial scanlines once added, since you basically get both: the artifical ones PLUS the natural ones.

Quote:
Of course this all assumes an idealized model where the system/game outputs a consistent frame rate, and there are no performance dips on the software side.

does this matter? The signal framerate remains the same. Doesn't really matter if the game drops a frame or not, does it?


Top
 Offline Profile  
 
 Post subject: Re: 31KHz CRT: 240p120 vs. 240p120 w/BFI vs. 480p60 w/ Scanl
PostPosted: Thu Feb 06, 2020 8:08 pm 


User avatar

Joined: 20 Aug 2016
Posts: 1477
Fudoh wrote:
does this matter? The signal framerate remains the same. Doesn't really matter if the game drops a frame or not, does it?


That depends.

For those that are very sensitive to flicker, it would be a deal breaker. Some users constantly remind me that they can't stand BFI blur reduction on digital displays. Those users are not going to like the flicker. I have used BFI on both LCDs and projectors, but some others find the flicker intolerable.

A native 60Hz refresh consistently scans the screen with a short vblanking reset. Adding black frames to 120Hz does more than darken the output, it (effectively) creates an artificial extended "vblank" and the result flickers much more than a native 60Hz output--because there are much longer intervals when the electron gun doesn't appear to be "drawing".

For some, I think it would matter.
_________________
We apologize for the inconvenience


Top
 Offline Profile  
 
 Post subject: Re: 31KHz CRT: 240p120 vs. 240p120 w/BFI vs. 480p60 w/ Scanl
PostPosted: Thu Feb 06, 2020 8:25 pm 


User avatar

Joined: 06 Mar 2006
Posts: 11998
Location: Germany
I agree on what you're saying, but that wasn't the answer to my question, was it?

I don't see how a performance dip would have any impact on this. Why would a framerate dip affect the overall impression of a 60Hz BFI video option, if the framerate dip doesn't affect the signal refresh rate. We're not talking vrr/freesync/gsync here, where a BFI function would be coupled to the actual software rendering framerate.


Top
 Offline Profile  
 
 Post subject: Re: 31KHz CRT: 240p120 vs. 240p120 w/BFI vs. 480p60 w/ Scanl
PostPosted: Thu Feb 06, 2020 9:09 pm 


User avatar

Joined: 06 Feb 2005
Posts: 833
Location: Italy
Fudoh wrote:
Quote:
The actual scanlines and blanklines width must be the same whether the CRT is displaying 240p120 or 480p60 with fake scanlines.

Why are you assuming this? I argued this before.

And I replied to you before :P obviously, blanklines in general will have a varying width depending on the vertical resolution - when above I said blanklines width was fixed I was only considering 240p120 and 480p with 100% scanlines. In both cases, the number of active lines is the same, the screen real estate is the same, the CRT characteristics are the same - I can fathom them looking differently only by taking into account perceptual reasons.


Top
 Offline Profile  
 
 Post subject: Re: 31KHz CRT: 240p120 vs. 240p120 w/BFI vs. 480p60 w/ Scanl
PostPosted: Thu Feb 06, 2020 9:10 pm 



Joined: 14 Aug 2017
Posts: 787
Fudoh wrote:
I don't see how a performance dip would have any impact on this. Why would a framerate dip affect the overall impression of a 60Hz BFI video option, if the framerate dip doesn't affect the signal refresh rate. We're not talking vrr/freesync/gsync here, where a BFI function would be coupled to the actual software rendering framerate.


I only mentioned that because I've seen RA's BFI at work. The BFI flicker was imperceptible other than by the decreased brightness, but during performance dips the image blank out or flicker visibly. I don't remember exactly how it looks like since this was a good while ago, but it was noticeable and bothersome. With a really powerful PC this may not be much of an issue very frequently though, but it was enough to make me not want to try that route again.


Top
 Offline Profile  
 
 Post subject: Re: 31KHz CRT: 240p120 vs. 240p120 w/BFI vs. 480p60 w/ Scanl
PostPosted: Thu Feb 06, 2020 9:20 pm 


User avatar

Joined: 06 Mar 2006
Posts: 11998
Location: Germany
Quote:
when above I said blanklines width was fixed I was only considering 240p120 and 480p with 100% scanlines. In both cases, the number of active lines is the same, the screen real estate is the same, the CRT characteristics are the same - I can fathom them looking differently only by taking into account perceptual reasons.

can't agree, sorry. The difference here is that the cathode ray draws twice the number of rows per frame on a 480p signal. When you say "blanklines in general will have a varying width depending on the vertical resolution" you basically confirm it, then why don't you think it applies to this very example?

I mean you just need to extrapolate the idea: let the resolution be 960p instead with thick scanlines with an active to blank ratio of 1:3. And now listen to yourself: "the number of active lines is the same...". The point where you're off I guess is the "screen real estate" which differs, even between 240p120 and 480p w/ 100% scanlines.


Top
 Offline Profile  
 
 Post subject: Re: 31KHz CRT: 240p120 vs. 240p120 w/BFI vs. 480p60 w/ Scanl
PostPosted: Thu Feb 06, 2020 9:41 pm 


User avatar

Joined: 25 May 2014
Posts: 562
Xer Xian wrote:
Look you guys, I am willing to concede that the perceived width of the blanklines might be a tiny bit smaller as a result of the increased brightness (which is a perceptual, subjective attribute - as opposed to luminance, which is a measurable quantity). The actual scanlines and blanklines width must be the same whether the CRT is displaying 240p120 or 480p60 with fake scanlines.

I think that argument only works if you assume a perfect electron beam "dot" with infinitely sharp edges. In practice, the dot probably has a zone around it where the intensity goes down with increasing distance from the center, which results in partial activation of the phosphors. However, the relation between the amount of energy dumped into the phosphor by the electron beam and the luminosity generated by it is not linear (which is one of the reasons Gamma correction exists), so the width of the illuminated area can vary.
_________________
GCVideo releases: https://github.com/ikorb/gcvideo/releases


Top
 Offline Profile  
 
 Post subject: Re: 31KHz CRT: 240p120 vs. 240p120 w/BFI vs. 480p60 w/ Scanl
PostPosted: Thu Feb 06, 2020 10:09 pm 


User avatar

Joined: 06 Feb 2005
Posts: 833
Location: Italy
Quote:
When you say "blanklines in general will have a varying width depending on the vertical resolution" you basically confirm it, then why don't you think it applies to this very example?

But it does - 240p120 and 480p w/ 100% scanlines have the same actual vertical resolution. Yes, technically the electron gun swipes twice the times at 480p but why would that matter at all.

Quote:
However, the relation between the amount of energy dumped into the phosphor by the electron beam and the luminosity generated by it is not linear (which is one of the reasons Gamma correction exists), so the width of the illuminated area can vary.

I understand this. Depending on the voltage level of signal even sources that have the same timings can have scanlines with a varying thickness. Fine - but this doesn't explain why 240p120 and 480p w/ 100% scanlines should look different for the same content being displayed for reason different than perceptions, does it?

I might well be too tired or too stupid to catch your point though you guys :lol: I'm off to bed, sorry


Top
 Offline Profile  
 
 Post subject: Re: 31KHz CRT: 240p120 vs. 240p120 w/BFI vs. 480p60 w/ Scanl
PostPosted: Thu Feb 06, 2020 10:11 pm 


User avatar

Joined: 16 Jan 2014
Posts: 734
Fudoh wrote:
I agree on what you're saying, but that wasn't the answer to my question, was it?

I don't see how a performance dip would have any impact on this. Why would a framerate dip affect the overall impression of a 60Hz BFI video option, if the framerate dip doesn't affect the signal refresh rate. We're not talking vrr/freesync/gsync here, where a BFI function would be coupled to the actual software rendering framerate.



Yeah, what I think he has experienced was the BFI feature of RA somehow experiencing a frame dip rather than say, a game engine frame rate drop or "slowdown" that you would experience for example in Gradius 3 for SNES. The SNES CPU not being able to sustain 60 fps of sprite animation or background scrolling has zero impact on the BFI function, as you would imagine. But I suppose if the PC running RA were to suddenly attempt to run some other taxing software while running RA (not sure why this would ever happen unless using 2 or more monitors), that the RA software BFI might not keep up with the 120Hz frame alternation??

In any case, if thats possible I have not yet experienced it, though when entering and exiting RA and 240p BFI modes you never quite know what Windows will choose to stick you with on your desktop. I have also had the RA software load up with windows desktop resolution of 1024x768 60Hz and run BFI in that mode, which will very likely give you a seizure if you dont exit quickly enough! :mrgreen:


Top
 Offline Profile  
 
 Post subject: Re: 31KHz CRT: 240p120 vs. 240p120 w/BFI vs. 480p60 w/ Scanl
PostPosted: Thu Feb 06, 2020 10:15 pm 


User avatar

Joined: 06 Mar 2006
Posts: 11998
Location: Germany
Right, but this becomes a non-issue once BFI is moved to an external processing device like the OSSC Pro.


Top
 Offline Profile  
 
 Post subject: Re: 31KHz CRT: 240p120 vs. 240p120 w/BFI vs. 480p60 w/ Scanl
PostPosted: Thu Feb 06, 2020 10:47 pm 


User avatar

Joined: 16 Jan 2014
Posts: 734
Xer Xian wrote:

Quote:
240p120 with BFI = 1 image frame every 1/120 sec followed by 1 black frame every 1/120 sec.


Then your CRT is not displaying repeated frames. BFI on a CRT does not improve motion in any (direct) way. It only improves it in this specific case because it alters the source signal by removing the frames that cause the effect in the first place. That's not how BFI is supposed to work.


I think you are not quite understanding BFI and why its used in RA. Its like this-- 60fps content that is frame doubled to display at 120Hz on a CRT is displaying each unique output frame twice on the monitor. The electron beam is sweeping the entire screen 2x before a new content frame is displayed. BFI, on RA, inserts a black frame in the second scan of the beam instead of displaying the content twice in a row. Im not sure why you are arguing that this doesnt improve the double strobe effect on CRTs, because thats what it does and indeed thats one of the very reasons it was implemented-- the other is being able to achieve 60Hz CRT motion quality on 60 fps content on an LCD.


Xer Xian wrote:
This should also answer your question on 240p120 w/ BFI on LCDs. Proper BFI of a 120hz signal requires a refresh rate of 240hz to work. If your source outputs 240p120 and your LCD does proper 120hz BFI then it is essentially (badly) mimicking a CRT and you'll end up with the same double-image effect (plus whatever blur is inherent in the specific LCD panel and the residual persistence of vision). If your LCD does 60hz BFI and refreshes at 120hz then it must discard half the frames and what is the point of feeding it frame doubled 240p in the first place then?


See above. On an LCD, the point is to completely eliminate motion blur. You are confusing 120Hz screen refresh with 120fps content. Yes, 120fps content displayed at a 240Hz refresh would require 1 black frame inserted every other 1/240th of a second, with the 120fps content being displayed at every 1/240th of a second that the black frame is not. Its the exact same principle as BFI used on 60fps content displayed at a 120Hz refresh. I dont know why you keep going back to this, lol, do you know of any vintage game console that has content frame rates of 120fps??


Top
 Offline Profile  
 
 Post subject: Re: 31KHz CRT: 240p120 vs. 240p120 w/BFI vs. 480p60 w/ Scanl
PostPosted: Thu Feb 06, 2020 10:49 pm 


User avatar

Joined: 16 Jan 2014
Posts: 734
Fudoh wrote:
Right, but this becomes a non-issue once BFI is moved to an external processing device like the OSSC Pro.


Thats what Im thinking. In any case, I guess I need to load up Gradius 3 or Super R Type and check some slowdown and verify nothing fishy happens! :D


Top
 Offline Profile  
 
 Post subject: Re: 31KHz CRT: 240p120 vs. 240p120 w/BFI vs. 480p60 w/ Scanl
PostPosted: Thu Feb 06, 2020 11:00 pm 


User avatar

Joined: 20 Aug 2016
Posts: 1477
Josh128 wrote:
Fudoh wrote:
Right, but this becomes a non-issue once BFI is moved to an external processing device like the OSSC Pro.


Thats what Im thinking. In any case, I guess I need to load up Gradius 3 or Super R Type and check some slowdown and verify nothing fishy happens! :D


I doubt that would create an issue. You would be more likely to encounter frame rate issues if you tried installing a major Windows update while gaming.
_________________
We apologize for the inconvenience


Top
 Offline Profile  
 
 Post subject: Re: 31KHz CRT: 240p120 vs. 240p120 w/BFI vs. 480p60 w/ Scanl
PostPosted: Thu Feb 06, 2020 11:34 pm 


User avatar

Joined: 16 Jan 2014
Posts: 734
orange808 wrote:
Josh128 wrote:
Fudoh wrote:
Right, but this becomes a non-issue once BFI is moved to an external processing device like the OSSC Pro.


Thats what Im thinking. In any case, I guess I need to load up Gradius 3 or Super R Type and check some slowdown and verify nothing fishy happens! :D


I doubt that would create an issue. You would be more likely to encounter frame rate issues if you tried installing a major Windows update while gaming.


I agree, but due to reports that the effect gets worse on impulsed displays as the ratio of frame rate to refresh decreases, I figure its worth a look. Essentially I should be able to test easily by loading a 30fps game such as SM64 or Streets of Rage which always run at 30Hz. Heck I could try Starfox and check its gnarly 10-15 fps for that matter. :mrgreen:

Image


Top
 Offline Profile  
 
 Post subject: Re: 31KHz CRT: 240p120 vs. 240p120 w/BFI vs. 480p60 w/ Scanl
PostPosted: Fri Feb 07, 2020 4:01 am 


User avatar

Joined: 16 Jan 2014
Posts: 734
As expected, running some good old 30fps Streets of Rage @120Hz looked the same to me as it does running a real Genesis on an NTSC CRT. BFI on or off, I saw no anomalies with the animation, you can discern the individual frames just like you always could.

Running this game in particular though, I must say the brightness difference between standard 240p120 and either 480p60 w/ scanlines or 240p120 w/ BFI is HUGE. The standard 120Hz mode looks SOOOO much better, IMO.


Top
 Offline Profile  
 
 Post subject: Re: 31KHz CRT: 240p120 vs. 240p120 w/BFI vs. 480p60 w/ Scanl
PostPosted: Fri Feb 07, 2020 7:18 am 


User avatar

Joined: 06 Feb 2005
Posts: 833
Location: Italy
Josh128 wrote:
I think you are not quite understanding BFI and why its used in RA. Its like this--

You've got to be kidding me now, because you explained to me exactly what I wrote in my post before yours.

Quote:
You are confusing 120Hz screen refresh with 120fps content.

I am not confusing anything with anything else. On the contrary, you are confusing frame doubling with BFI, or at least using wrong terminology. 60Hz BFI for 240p content (or any content running at 60fps) does not need or benefit from frame doubling, it just requires a black frame inserted every other frame. No one calls that frame doubling. It's another thing altogether. If you call for a frame doubling feature for use on CRTs while also saying that with BFI it will improve motion on flat panels as well, people (like me) could genuinely think that you want to have both at the same time and will tell you that that is dumb.


Top
 Offline Profile  
 
 Post subject: Re: 31KHz CRT: 240p120 vs. 240p120 w/BFI vs. 480p60 w/ Scanl
PostPosted: Fri Feb 07, 2020 2:07 pm 


User avatar

Joined: 16 Jan 2014
Posts: 734
Xer Xian wrote:
Josh128 wrote:
I think you are not quite understanding BFI and why its used in RA. Its like this--

You've got to be kidding me now, because you explained to me exactly what I wrote in my post before yours.

Quote:
You are confusing 120Hz screen refresh with 120fps content.

On the contrary, you are confusing frame doubling with BFI, or at least using wrong terminology. 60Hz BFI for 240p content (or any content running at 60fps) does not need or benefit from frame doubling, it just requires a black frame inserted every other frame. No one calls that frame doubling. It's another thing altogether. If you call for a frame doubling feature for use on CRTs while also saying that with BFI it will improve motion on flat panels as well, people (like me) could genuinely think that you want to have both at the same time and will tell you that that is dumb.


Show me, please, in this thread, where I called frame doubling BFI. Where did I say, and I quote-

Xer Xian wrote:
"60Hz BFI for 240p content (or any content running at 60fps) does not need or benefit from frame doubling, it just requires a black frame inserted every other frame. No one calls that frame doubling.If you call for a frame doubling feature for use on CRTs while also saying that with BFI it will improve motion on flat panels as well, people (like me) could genuinely think that you want to have both at the same time and will tell you that that is dumb."

Go!



Finally, to cite an outside source to show that RAs BFI does indeed eliminate motion blur on 60fps content on 120Hz capable LCDs, and also eliminates the stroboscopic illusion of running 60fps content at 120Hz
on CRTs, contrary to what you have claimed, here you go. And before you come back and say you havent claimed that, I'll quote you again:

Xer Xian wrote:
The double-image effect of repeated frames on a CRT cannot be alleviated with BFI.


https://emulation.gametechwiki.com/inde ... _insertion

Image


Top
 Offline Profile  
 
Display posts from previous:  Sort by  
Post new topic Reply to topic  [ 81 posts ]  Go to page 1, 2, 3  Next

All times are UTC


Who is online

Users browsing this forum: drboom and 13 guests


You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum

Search for:
Jump to:  
Space Pilot 3K template by Jakob Persson
Powered by phpBB © 2000, 2002, 2005, 2007 phpBB Group