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 Post subject: Does the NESRGB preserve the picture quality of the NES?
PostPosted: Fri Jun 28, 2019 2:11 am 



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Does the NESRGB mod change (or corrupt) the picture quality of the Nintendo NES?
I know that RGB looks way better than composite video, but I am referring to the internal picture quality instead.

What I am specifically asking is this...
With an unmodified Nintendo NES, are the red, green, blue, and sync signals that go into the yellow RCA composite video cable the exact same as the red, green, blue, and CSYNC signals that come out of the RGB port on a NESRGB modded Nintendo NES?

I am just asking out of curiosity before I start some new projects where I will be reworking and modifying retro Nintendo consoles. :o


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 Post subject: Re: Does the NESRGB preserve the picture quality of the NES?
PostPosted: Fri Jun 28, 2019 4:45 am 



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erik343 wrote:
With an unmodified Nintendo NES, are the red, green, blue, and sync signals that go into the yellow RCA composite video cable the exact same as the red, green, blue, and CSYNC signals that come out of the RGB port on a NESRGB modded Nintendo NES?

I would think it's difficult answer that, because, to my [limited] understanding, the NES's PPU directly generates composite video, so I'd say it's somewhere between difficult and impossible for us to compare any RGB video inside the PPU to what comes out of the NESRGB. (Might be possible to build a virtual version of the PPU in an emulator and peek inside, but I imagine that would be impractical with real hardware.)

As for how the output of an unmodified NES compares to the NESRGB, the NESRGB is going to be clearer and sharper, because it's not going to be composite video; and the color palettes may not be 100% spot-on. (Admittedly, I haven't personally compared any of the color palettes to stock composite video output.)


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 Post subject: Re: Does the NESRGB preserve the picture quality of the NES?
PostPosted: Fri Jun 28, 2019 6:12 am 


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Because there is no RGB generated by the NES, the colors have to be approximated in the RGB color space. What's worse is any given TV will do its own conversion of the composite video signal and you end up with different color variations from set to set. Check out my web page of various NTSC palettes I made:

http://www.firebrandx.com/nespalette.html

Note the first image is a good approximation of PAL (on the left) versus typical NTSC behavior (on the right).
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 Post subject: Re: Does the NESRGB preserve the picture quality of the NES?
PostPosted: Fri Jun 28, 2019 6:54 am 


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As the NES generates colors in the NTSC domain directly, it doesn’t operate on RGB at any point originally, unlike later systems that encode RGB. So, just as with every emulator, creating an appropriate RGB palette is an interpretive exercise. This is often informed by captures from real systems, but it is intrinsically not exactly the same. In theory, an RGB palette can represent exactly how it appears on a given television. After all, the television itself decides composite into RGB.
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 Post subject: Re: Does the NESRGB preserve the picture quality of the NES?
PostPosted: Fri Jun 28, 2019 10:06 am 


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mikejmoffitt wrote:
After all, the television itself decides composite into RGB.


Although I ran into a problem with this in that there was no way to reproduce the "SMB Sky" on a PVM with RGB feed. I ran an unmodded NES through the same PVM, and that sky has an almost neon blue glow. Any attempt to replicate it in RGB feed resulted in either too dark a color, or a washed out color. It was as if the blue intensity was outside the range of 0 - 255 RGB scale. So if it were simply a case of the TV doing a simple clipped conversion to RGB, I should have been able to easily replicate the color. It was in fact impossible to replicate.
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 Post subject: Re: Does the NESRGB preserve the picture quality of the NES?
PostPosted: Fri Jun 28, 2019 10:41 am 


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FBX wrote:
What's worse is any given TV will do its own conversion of the composite video signal and you end up with different color variations from set to set.


Hum interesting I didn't know that, is it the same thing with S-Video?


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 Post subject: Re: Does the NESRGB preserve the picture quality of the NES?
PostPosted: Fri Jun 28, 2019 1:52 pm 



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Lawfer wrote:
FBX wrote:
What's worse is any given TV will do its own conversion of the composite video signal and you end up with different color variations from set to set.


Hum interesting I didn't know that, is it the same thing with S-Video?


In my experience, all other factors being equal, compared to RGB, S-video should result in colors closer to composite output.

Composite (when wired that way) and S-video output from the NESRGB are both encoded from the RGB output, but with the former two you are still letting the NTSC decoder of your TV/monitor do the main work. Lately I've found S-video from the NESRGB, combined with the right palette, to be the best compromise of picture clarity and "NTSC colors" (of my particular monitor).


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 Post subject: Re: Does the NESRGB preserve the picture quality of the NES?
PostPosted: Fri Jun 28, 2019 3:23 pm 



Joined: 13 Jan 2018
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Thank you so much, I was very curious lol.
My next project is to recap my NES and then RGB mod it.
I bought a very nice Hakko soldering station and desoldering station.


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 Post subject: Re: Does the NESRGB preserve the picture quality of the NES?
PostPosted: Fri Jun 28, 2019 6:15 pm 


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FBX wrote:
mikejmoffitt wrote:
After all, the television itself decides composite into RGB.


Although I ran into a problem with this in that there was no way to reproduce the "SMB Sky" on a PVM with RGB feed. I ran an unmodded NES through the same PVM, and that sky has an almost neon blue glow. Any attempt to replicate it in RGB feed resulted in either too dark a color, or a washed out color. It was as if the blue intensity was outside the range of 0 - 255 RGB scale. So if it were simply a case of the TV doing a simple clipped conversion to RGB, I should have been able to easily replicate the color. It was in fact impossible to replicate.


In this situation, you could reduce the intensity of other colors, so as to make this one stand out in proportion. The 0-255 RGB scale is only a scale of proportions.
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 Post subject: Re: Does the NESRGB preserve the picture quality of the NES?
PostPosted: Fri Jun 28, 2019 11:27 pm 


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But then the colors will appear too dark. As of now the colors look pretty good and to be honest the darker blue is not really noticeable unless you do a side by side comparison.
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 Post subject: Re: Does the NESRGB preserve the picture quality of the NES?
PostPosted: Sat Jun 29, 2019 10:27 am 


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It's not colors, I believe it's the subcarrier haze coming thru causing the fluro neon effect


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 Post subject: Re: Does the NESRGB preserve the picture quality of the NES?
PostPosted: Sun Jun 30, 2019 6:07 am 


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mikejmoffitt wrote:

In this situation, you could reduce the intensity of other colors, so as to make this one stand out in proportion. The 0-255 RGB scale is only a scale of proportions.


You should know me by now that I would have exhausted this and all other methods before giving up. ;-)

None of them work. For whatever the reason, there's 4 entries in that blue spectrum that CANNOT be reproduced in the RGB feed, with the SMB sky being the most blatant. Maybe it is subcarrier haze, or maybe it's how the voltage is handled for the RGB lines from the internal encoder versus external RGB feed, but whatever the reason, it can't be replicated. Toning down the rest of the palette to compensate only makes everything look wrong. In all reality, my 'Smooth' palette is the closest one can get on a PVM to unmodded NTSC feed.
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 Post subject: Re: Does the NESRGB preserve the picture quality of the NES?
PostPosted: Sun Jun 30, 2019 7:23 pm 


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All we can hope for is that someone discovers a mod that safely overdrives the blue like a stock NES...if that's even possible.

To the OP question, Composite looks better on a RGB modded NES compared to a stock one. It looks cleaner with less noticeable dot crawl.
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 Post subject: Re: Does the NESRGB preserve the picture quality of the NES?
PostPosted: Mon Jul 01, 2019 3:27 am 



Joined: 01 Jul 2017
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I believe later model PVMs and certainly consumer TVs decode composite video in the digital domain and output a BT.656 YPbPr stream to a DAC that drives the guns. Assuming the final output still looks 'okay' then it should be possible to recreate the corresponding RGB values?


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 Post subject: Re: Does the NESRGB preserve the picture quality of the NES?
PostPosted: Mon Jul 01, 2019 3:20 pm 


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mikechi2 wrote:
I believe later model PVMs and certainly consumer TVs decode composite video in the digital domain and output a BT.656 YPbPr stream to a DAC that drives the guns. Assuming the final output still looks 'okay' then it should be possible to recreate the corresponding RGB values?


Well I tried on a 20M2U and it wasn't possible. Not sure if that counts as a later model.
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 Post subject: Re: Does the NESRGB preserve the picture quality of the NES?
PostPosted: Mon Jul 01, 2019 11:03 pm 



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FBX wrote:
mikechi2 wrote:
I believe later model PVMs and certainly consumer TVs decode composite video in the digital domain and output a BT.656 YPbPr stream to a DAC that drives the guns. Assuming the final output still looks 'okay' then it should be possible to recreate the corresponding RGB values?


Well I tried on a 20M2U and it wasn't possible. Not sure if that counts as a later model.


I just skimmed the manual and it seems like it's an analog design. What did you try exactly?


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 Post subject: Re: Does the NESRGB preserve the picture quality of the NES?
PostPosted: Tue Jul 02, 2019 12:46 am 



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It would actually be pretty funny if it turns out to be relatively simple to get those RGB values, after it had been presumed to be impossible all this time. Hopefully it is because honestly there's no satisfactory RGB palette currently available.


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 Post subject: Re: Does the NESRGB preserve the picture quality of the NES?
PostPosted: Tue Jul 02, 2019 8:03 am 


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mikechi2 wrote:

I just skimmed the manual and it seems like it's an analog design. What did you try exactly?


I used an unmodded NES running a fullscreen color test ROM fed into the composite jack of the PVM. I then simultaneously ran an Nt Mini into the RGB feed with the same color test rom. Then from there, I used the SD card to load in palette changes until each color was as close as could be matched as possible. That resulted in the "Smooth" palette, but again, the SMB sky color had to be approximated because it was impossible to dial in with direct RGB. The blue phosphor was very intense on the composite video for that sky color, whereas you could never get it anywhere near that intense on the RGB video input.

fernan1234 wrote:
It would actually be pretty funny if it turns out to be relatively simple to get those RGB values, after it had been presumed to be impossible all this time. Hopefully it is because honestly there's no satisfactory RGB palette currently available.


It's not presumed. It's a technological FACT. Case in point is the Playchoice-10 color palette. Since the PPU for those machines did have internally generated RGB, the values were quickly documented.
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 Post subject: Re: Does the NESRGB preserve the picture quality of the NES?
PostPosted: Tue Jul 02, 2019 9:06 am 


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FBX wrote:
I used an unmodded NES running a fullscreen color test ROM fed into the composite jack of the PVM. I then simultaneously ran an Nt Mini into the RGB feed with the same color test rom. Then from there, I used the SD card to load in palette changes until each color was as close as could be matched as possible.

From what I have read online the Nt Mini is an FPGA design, so I guess its not possible to know exactly how the RGB is generated internally. For instance maybe the Nt Mini is deliberately clipping the RGB values somewhere in the pipeline, perhaps so that limited range HDMI or the OSD can be used? (Please note that this is not a criticism but merely a suggestion)


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 Post subject: Re: Does the NESRGB preserve the picture quality of the NES?
PostPosted: Tue Jul 02, 2019 9:27 am 


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Link83 wrote:
FBX wrote:
I used an unmodded NES running a fullscreen color test ROM fed into the composite jack of the PVM. I then simultaneously ran an Nt Mini into the RGB feed with the same color test rom. Then from there, I used the SD card to load in palette changes until each color was as close as could be matched as possible.

From what I have read online the Nt Mini is an FPGA design, so I guess its not possible to know exactly how the RGB is generated internally. For instance maybe the Nt Mini is deliberately clipping the RGB values somewhere in the pipeline, perhaps so that limited range HDMI or the OSD can be used? (Please note that this is not a criticism but merely a suggestion)


That really shouldn't matter. The Nt Mini's RGB output matches the intended color values I fed it when you re-capture back into a lossless card like the E1S. So whether it's FPGA or not, the color output is accurate to the hex value used.
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 Post subject: Re: Does the NESRGB preserve the picture quality of the NES?
PostPosted: Tue Jul 02, 2019 9:37 am 


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FBX wrote:
Case in point is the Playchoice-10 color palette. Since the PPU for those machines did have internally generated RGB, the values were quickly documented.


Here are some of the most common the RGB PPU:

RP2C03B: Playchoice-10
RC2C05-99: Sharp Famicom Titler AN-510


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 Post subject: Re: Does the NESRGB preserve the picture quality of the NES?
PostPosted: Fri Jul 05, 2019 7:44 am 



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It's interesting: when I use FBX's Composite Direct palette on my NESRGB outputting to an RGB cable, the SMB sky is purple, as we all know. But if I instead use the NESRGB's (RGB-encoded) composite output with the same palette, the sky ends up blue again.

You could perhaps consider the blue sky to be just another artifact of composite video, like dot crawl or color bleed.


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 Post subject: Re: Does the NESRGB preserve the picture quality of the NES?
PostPosted: Fri Jul 05, 2019 12:24 pm 



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copy wrote:
It's interesting: when I use FBX's Composite Direct palette on my NESRGB outputting to an RGB cable, the SMB sky is purple, as we all know. But if I instead use the NESRGB's (RGB-encoded) composite output with the same palette, the sky ends up blue again.

You could perhaps consider the blue sky to be just another artifact of composite video, like dot crawl or color bleed.


Yes this is expected because as mentioned earlier, when you use composite (and S-video) the colors you see are not the direct result of the NESRGB palette used but also the NTSC decoder in your TV or monitor. That's why while I don't enjoy any of the palettes when used directly through RGB, several can look quite good (better matching what I'm used to) via composite and S-video.


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 Post subject: Re: Does the NESRGB preserve the picture quality of the NES?
PostPosted: Mon Jul 08, 2019 8:53 pm 


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erik343 wrote:
Thank you so much, I was very curious lol.
My next project is to recap my NES and then RGB mod it.
I bought a very nice Hakko soldering station and desoldering station.


I just did it about 6 months ago and I think it looks great.

Depending on what you are using as a monitor, you may prefer one of the non-standard color pallets. When I'm using my projector, I think the "improved" color pallet looks the best. Because the NES wasn't designed with newer displays in mind, trying to make it look perfectly like a composite CRT just doesn't make sense to me. Newer display technologies have their own strengths and weaknesses and you're never going to get the 1:1 experience of a CRT.


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 Post subject: Re: Does the NESRGB preserve the picture quality of the NES?
PostPosted: Tue Jul 09, 2019 7:23 pm 


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vol.2 wrote:

Depending on what you are using as a monitor, you may prefer one of the non-standard color pallets. When I'm using my projector, I think the "improved" color pallet looks the best. Because the NES wasn't designed with newer displays in mind, trying to make it look perfectly like a composite CRT just doesn't make sense to me. Newer display technologies have their own strengths and weaknesses and you're never going to get the 1:1 experience of a CRT.


It's mostly for nostalgia. There is no right or wrong answer as to which palette you use since the NES never supported RGB and every tv would give a slightly different result.
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