Analogue Super NT

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Locutus73
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Re: Analogue Super NT

Postby Locutus73 » Fri Feb 16, 2018 3:51 pm

Newsdee wrote:The XRGB Framemeister is hands down the best upscaler I've used. It's pricey but it has taken absolutely everything that I threw at it. Yes, it has one to two frames of lag but they are negligible compared to emulators. The Super NT has a few upscaling modes to allow the user to choose - either use framebuffers (taking some minor lag) or a raw direct mode without any upscaling.

Yep, they call this setting “Buffer Mode” and it has three options:
1) Zero Delay: the emulated/simulated SNES is slowed form 60.098Hz to 60Hz, a small loss in accuracy (the game loses 1 second each 10 minutes) traded for a perfect video timing
2) Single Buffer: the emulated/simulated SNES runs at 60.098Hz, but produces a 60Hz video output with some screen tearing
3) Fully Buffered: the emulated/simulated SNES runs at 60.098Hz, but produces a 60Hz video output without tearing, but once in a while a full frame is dropped

Newsdee wrote:Now, the problem with line doublers is that they don't do anything to adjust the video frequency, which is usually the Achilles' heel of many displays. The XRGB will output a stead 60hz video no matter what you give it. So the OSSC woudl be pretty useless for a MiST for instance. I suppose it is still as linedoubler for original systems though, and is better than other options (such as GBS 8220).

Sorgelig wrote:You are missing one important point: it's HDMI output. In VGA you still can find very tolerant displays able to show 50Hz and even 48Hz(ZX, BK0011M, Vector06C, etc). In HDMI world i even not sure if such tolerant displays exist.
It doesn't matter what is your primary concern, if you want a lag free scan doubler or not. If you cannot use such non-standard HDMI output with your TV/Display, then it's completely useless. And chances to get a non-working solution with OSSC is very high if you intend to use it with retro core with non-strictly standard TV output.

I’m not missing anything, I know perfectly that OSSC can have sync problems with some displays, producing nonstandard HDMI timings. I’m affirming that it’s a non-cost-effective, non-practical tool for enthusiast hobbyists pursuing a specific feature, regardless of all possible problems. We are talking about first-world problems. I mean, whatever the hobby, when you get in the enthusiast/fanatical realm, it’s full of esoteric/extreme products not suitable for the general audience. The first hobby that comes in my mind is the audiophile world where an OSSC could be compared to a non-oversampling DAC (please take this example with a grain of salt), for people that want a DAC with less features (it doesn’t oversample like any good sounding DAC), because they want to apply esoteric oversampling algorithms with their software players. Another hobby could be motorcycling, where someone prefers old school bikes, without any electronic driving assistance, because they feel raw and brutal, despite being unpractical and dangerous. Do we want to talk about cycling where someone prefers fixed-gear bikes? Everyone buying OSSC should know that it can have sync problems and this should be a risk willingly assumed in order to get the “purest, most faithful and lagless timings” with the right display. I think, since the more safe XRBG mini already exists, it’s good to be able to have an hard-core alternative. To each one his own.


Sorgelig wrote:As i've told above, a simple scandoubler inside the core can do the same lag-free up-scaling. Someone can try to make it with HDMI output. It's not my style.
The whole point of HDMI output on MiSTer is to make a plug-n-play system, not another quest of finding a compatible monitors.

P.S.: VIP scaler can do framebuffer-less scaling which means it can be used for lag-free upscaling. Some systems can have a special version of scaler if system provides guaranteed standard 50/60 fps. This option need to be explored and suitable for cores with dedicated developers as it require more tight integration and special tweaks.


Having a plug-n-play system is a sensible approach for sure.
Ideally a system providing all possible options could provide an “original frequency zero delay” mode, similar to OSSC, with possible incompatibilities and three other modes similar to the Super NT’s ones. The more choices the better… anyway we are talking about open source hobby projects where anyone (in MiSTer case anyone has a specific name :D ) is donating its spare time, so specific choices have to be taken.

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Re: Analogue Super NT

Postby Newsdee » Sat Feb 17, 2018 12:23 am

Don't get me wrong, I'm glad the OSSC exists as the XRGB is getting rarer and there is no replacement in sight, and also since it is fully open source and documented hardware.

It isn't cheap though, so I can only recommend saving the money for an XRGB if you can get one. If not, OSSC is still a very decent machine if you own many original systems (which is prpbably the case of many of us) I wouldn't recommend getting it just for the MiST or MiSTer, though.

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Re: Analogue Super NT

Postby ijor » Sat Feb 17, 2018 1:38 am

Since some people here seem to have quite some experience with the issue. What you would recommended for an affordable decent VGA to HDMI upscaler with frame buffer? I don't mind the lag at all, but I do need/want refresh rate conversion . I'm looking for something affordable, the OSSC and the XRGB are both way too expensive.

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Re: Analogue Super NT

Postby Locutus73 » Sat Feb 17, 2018 10:21 am

Getting back on Super NT, not exactly a jailbreak in the sense of a hack opening the board to new cores, neither something coming directly from Kevtris (at least officially), but here it is:
https://github.com/SmokeMonsterPacks/Super-NT-Jailbreak
It was fast!

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Last edited by Locutus73 on Sat Feb 17, 2018 4:11 pm, edited 1 time in total.

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Re: Analogue Super NT

Postby Sorgelig » Sat Feb 17, 2018 10:42 am

ijor wrote:Since some people here seem to have quite some experience with the issue. What you would recommended for an affordable decent VGA to HDMI upscaler with frame buffer? I don't mind the lag at all, but I do need/want refresh rate conversion . I'm looking for something affordable, the OSSC and the XRGB are both way too expensive.

read this thread:
viewtopic.php?f=115&t=27019
i've posted a lot of my test results there.
In short: there is no universal scaler exists may be except XRGB-mini which i don't have. According to reviews i saw, XRGB-mini also has issues in supporting some resolutions.

I have plans to make a ADC daughter board for Terasic board and make a universal scaler based on VIP cores. But currently i have no time for that.

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Re: Analogue Super NT

Postby Locutus73 » Sat Feb 17, 2018 10:45 am

Newsdee wrote:Don't get me wrong, I'm glad the OSSC exists as the XRGB is getting rarer [...] I wouldn't recommend getting it just for the MiST or MiSTer, though.


Yep fair enough. Just for clarification: I don’t own either OSSC or XRGB, and I’m not a fanboy (a la Amiga 500 vs Atari ST) of either. I just own a DVDO iSCAN Mini, an HDMI in HDMI out scaler and video processor, I use on my projector in order to enhance Movies and TV series.

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Re: Analogue Super NT

Postby Locutus73 » Sat Feb 17, 2018 10:49 am

Sorgelig wrote:I have plans to make a ADC daughter board for Terasic board and make a universal scaler based on VIP cores. But currently i have no time for that.

:!: :!: :!:
You’re a powerhouse! Do you ever sleep?

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Re: Analogue Super NT

Postby Newsdee » Sat Feb 17, 2018 1:15 pm

ijor wrote:Since some people here seem to have quite some experience with the issue. What you would recommended for an affordable decent VGA to HDMI upscaler with frame buffer? I don't mind the lag at all, but I do need/want refresh rate conversion

Frame rate conversion is going to be the problem, not even the OSSC will handle that. I own an XRGB and it took everything I threw at it, but its expensive. Besides that, for a reasonable price you can get a Chinese GBS board variant like this one:
https://m.aliexpress.com/item/328384924 ... 2838492457

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Re: Analogue Super NT

Postby Sorgelig » Sat Feb 17, 2018 1:45 pm

No.. only not GBS82xx! This is one of worst scaler i've tried. A lot of simplifications of chip connections giving many HW problems. Firmware is rubbish.
I don't recommend these GBS boards.

P.S.: new GBS boards adds HDMI chip. There is a chance they use a better/updated firmware, but don't hope much.

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Re: Analogue Super NT

Postby Newsdee » Sat Feb 17, 2018 1:56 pm

It is what it is at $30, but it handles 50hz to 60hz conversion more or less decently. What else is there out there that can do that at a similar price?

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Re: Analogue Super NT

Postby Sorgelig » Sat Feb 17, 2018 2:14 pm

In my tests GBS couldn't handle many cores.

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Re: Analogue Super NT

Postby DrOG » Sat Feb 17, 2018 4:41 pm

I agree with Sorgelig, especially PAL cores are problematic. See my test results here:

viewtopic.php?f=115&t=27019&start=125

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Re: Analogue Super NT

Postby Newsdee » Sat Feb 17, 2018 8:37 pm

Right, so what do you recommend instead?

For cores that run at 60hz one can use a regular VGA to HDMI upscaler. The issue is converting 50hz to 60hz.

There is some hope for the GBS though:
https://shmups.system11.org/viewtopic.php?t=52172

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Re: Analogue Super NT

Postby Sorgelig » Sat Feb 17, 2018 9:37 pm

Newsdee wrote:There is some hope for the GBS though:
https://shmups.system11.org/viewtopic.php?t=52172

that's very old topic. It's already finished as i've wrote above with scripts for RPi. No firmware update is planing.

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Re: Analogue Super NT

Postby Locutus73 » Sat Feb 17, 2018 9:51 pm

Newsdee wrote:For cores that run at 60hz one can use a regular VGA to HDMI upscaler. The issue is converting 50hz to 60hz

Just out of curiosity: don’t modern USA TV sets support 50Hz through HDMI?

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Re: Analogue Super NT

Postby Newsdee » Sun Feb 18, 2018 1:14 am

They do. I had much better luck with a SCART to HDMI converter once I got rid of an old TV and the new one accepted 50hz.

But I'm just sticking to the original question about handling the conversion, for which not many options seem to exist. Next step above the GBS seems to be the XRGB, which works but is quite a leap in price.

Obviously the best is to handle it in the source machine itself as the MiSTer and Super NT do.

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Re: Analogue Super NT

Postby ijor » Sun Feb 18, 2018 2:14 am

Newsdee wrote:But I'm just sticking to the original question about handling the conversion, for which not many options seem to exist. Next step above the GBS seems to be the XRGB, which works but is quite a leap in price.


So those are the only two devices that perform frame buffer refresh rate conversion? I assumed cheap chinese converters wouldn't do it. But there are some devices in the $60 to $100+ range, some made in the US, that I expected they would. I am ready to pay for something in that range, just not the ridiculous price of the XRGB (well, ridiculous for my needs and purpose).

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Re: Analogue Super NT

Postby ijor » Sun Feb 18, 2018 2:18 am

Locutus73 wrote:Just out of curiosity: don’t modern USA TV sets support 50Hz through HDMI?


Even if they do, it doesn't mean it will accept the 50Hz non-standard signal produces by many retro systems. In some cases you might even need refresh rate conversion from 60Hz to 60Hz for this very same reason.

Btw, I also would like it for the 70Hz ST monochrome signal, but I guess that getting support for that would even be more difficult :(

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Re: Analogue Super NT

Postby Sorgelig » Sun Feb 18, 2018 2:18 am

I don't agree.
There are options much better than GBS and cheaper than XRGB.
Some LKV scalers are very good. Read my posts in VGA upscaling experiments thread.

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Re: Analogue Super NT

Postby ijor » Sun Feb 18, 2018 2:19 am

Sorgelig wrote:I don't agree.
There are options much better than GBS and cheaper than XRGB.
Some LKV scalers are very good. Read my posts in VGA upscaling experiments thread.


Thanks for the pointer. Will check that thread thoroughly.

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Re: Analogue Super NT

Postby Newsdee » Sun Feb 18, 2018 4:28 am

Looks like I forgot that the LKV362A could convert frequencies. Thats useful for the cores that can run without the scandoubler.

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Re: Analogue Super NT

Postby Locutus73 » Sun Feb 18, 2018 9:20 am

HDMI 2.1 supports Variable Refresh Rate, so, hopefully, in the future we’ll see TV sets perfect for modern and retro computing/gaming.

How does MiSTer (and other FPGA based platforms like Super NT and OSSC) implement HDMI? I mean: is it just an HDMI socket and some basic electronics (caps, resistors) connected to the FPGA, so that they’ll be potentially able to implement HDMI 2.1 VRR or am I missing something?

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Re: Analogue Super NT

Postby Sorgelig » Sun Feb 18, 2018 10:36 am

DE10-nano uses ADV7513 chip to create HDMI signal. This chip can produce any resolution and refresh rate.

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Re: Analogue Super NT

Postby Foxie » Sun Feb 18, 2018 5:15 pm

Generally in my experience, flat panel TVs tend to be more tolerant of different video timings than flat panel IBM monitors. TVs need to support both 50Hz and 60Hz, so the main problem would be handling systems with funny rates like 55Hz (some arcade games). If your panel can't accept 55Hz, then you're pretty much screwed unfortunately. Using a framebuffer to convert frame rate will result in absolutely horrendous jerking, you may as well just use an emulator. Converting from 49.9Hz (ST) to 50Hz should be pretty smooth though because you only repeat one frame every several hundred.

In theory, you could do a nicer job at frame rate conversion if you had a really powerful motion estimator. Some TVs use a motion estimator to boost the frame rate to 100Hz, so it's a similar idea to that - except making a much smaller adjustment. But motion estimators come at a price too - they introduce considerable lag (the better the conversion, the more frames you need to buffer to "look ahead") and do cause some visible artifacts when a sprite moves over a background. Visually, it's a similar effect to watching a Youtube video with sort of MPEG-ish artifacts. In theory, you could probably do a slightly better job of motion estimation on systems which have hardware sprites and hardware scrolling - since you have some extra graphics data in memory you can tap into to better predict in-between frames and the sprites are separate. But I'm not aware of anyone who's developed such an application-specific motion estimator.

Of course a good motion estimator would use a massive amount of FPGA logic resources. I don't know what size FPGA would be needed, but I expect it would need to be towards the upper end of the market. There's a huge amount of processing to be done - doing it on a CPU like an i7 is really difficult. It might be easier to do it on a high-end GPU in conjunction with an emulator.

This problem will go away in the future, because we'll all have 600Hz TVs which accept 600Hz through an input. 600Hz divides nicely into all the important frame rates which is why some TV manufacturers use it as the internal panel refresh frequency.

My plasma TV will accept 50 or 60Hz via SCART or HDMI and displays it without artifacts. But unfortunately, if you feed it a VGA signal at 70Hz it frame rate converts it using a simple frame buffer (no motion estimation) back down to 60Hz. That makes it completely unsuitable for DOS demos. A shame, because the motion on plasma is pretty much as smooth as CRT when no frame rate conversion is happening.

Generally though, I think most people would be much better served by picking up an old 15kHz CRT monitor and using that instead of messing around with flat panels. You will get far better motion than an LCD panel, better colours and it's the best retro experience. The Acorn, Philips and Atari monitors seem to be the sharpest in my experience, and you can also get broadcast monitors quite easily now - but be sure to get one with an RGB input card fitted. Younger people might complain about the annoying 15kHz whistle, but as I enter middle age I find I can barely hear it any more.

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Re: Analogue Super NT

Postby ijor » Mon Feb 19, 2018 1:55 pm

Locutus73 wrote:HDMI 2.1 supports Variable Refresh Rate, so, hopefully, in the future we’ll see TV sets perfect for modern and retro computing/gaming.
How does MiSTer (and other FPGA based platforms like Super NT and OSSC) implement HDMI? I mean: is it just an HDMI socket and some basic electronics (caps, resistors) connected to the FPGA, so that they’ll be potentially able to implement HDMI 2.1 VRR or am I missing something?


The DE-10 nano HDMI transmitter is not a passive component. As Sorgelig said, it's an Analog Device chip. This is a high level chip that even has a small integrated MPU that can automatically detect all standard video modes, among many other things. But it is quite flexible and, as officially specified in the manual, can accept non standard modes.

I think it probably remains to be seen if it would be compatible with HDMI 2.1 VRR. I don't know the low level details of VRR. Anyone have access to the specs or have seen a low level technical description? I understand it can accept an arbitrary refresh rate. But can it accept an arbitrary pixel clock as well? Or the refresh cycle must be a multiple of the standard pixel clock cycle for the given resolution?


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