Why horizontal resolution doesn’t really matter with CRTs?

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nes.og
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Why horizontal resolution doesn’t really matter with CRTs?

Post by nes.og »

Super resolutions for example.

Someone please schools me!
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Sumez
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Re: Why horizontal resolution doesn’t really matter with CRT

Post by Sumez »

Pretty vague question, but what I'm guessing you are getting at is the fact that the colors shown on a CRT are produced by a continuous beam moving horizontally across the screen. As the analog input signal changes colors in sync with the moving beam, the color that "sticks to the surface of the screen", ie the color you are seeing at that point, is taken from the signal at that moment in time.
This beam, and the CRT as a whole, has no perception of when the image data changes from one pixel to the next, that's all decided by whatever outputs the signal.

As such, a video game console, or an arcade game, etc. will have a clear definition of how many horizontal pixels exist, it's just the display doesn't. But there's still a realistic upper limit to how densely they can be packed and still be told apart.
nes.og
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Re: Why horizontal resolution doesn’t really matter with CRT

Post by nes.og »

Thanks for your response. You are right and I have probably have been too vague.

I hear that CRTs have a vertical resolution due to the number of lines but don’t have a horizontal resolution. For example 320x240 will look the same with a super resolution of 2560 x 240. I’m trying to understand how these would look the same?

Maybe your response has explained this but I’m still confused lol
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Sumez
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Re: Why horizontal resolution doesn’t really matter with CRT

Post by Sumez »

Those will definitely not look the same.
They will be displayed in the same aspect ratio (depending on the settings of the CRT), but the pixels will be much more densely packed in the 2560x240 image, allowing for a more detailed image. There will definitely be a noticeable difference between the two, even on most shittier TVs.
nes.og
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Re: Why horizontal resolution doesn’t really matter with CRT

Post by nes.og »

Interesting, I thought they would appear the same and the reason for super resolutions is to better support multiple 240P console resolutions within one resolution or quicker to switch resolutions with them?
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Josh128
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Re: Why horizontal resolution doesn’t really matter with CRT

Post by Josh128 »

I think the answer you are looking for is that the actual horizontal resolution of the CRT is limited by the horizontal output circuitry and is speed/bandwidth limited. It can only turn the RGB signals on and off so fast to produce color changes. If its limit is ~400 per line, then displaying that same line image in a 2560 pixel wide line wont appear any different in practice. 1 "pixel" of a SNES game would just be represented by ~6 or 7 pixels in the digital image that is sampled to be sent to the screen.

The goal of super-res is to prevent horizontal shimmer in moving graphics from mismatched source and output resolutions with one catch-all mode rather than try to match each different possible horizontal resolution perfectly, as in arcade games for example. So instead of needing 200+ different resolutions for 1000 different arcade games, you can just keep the super horizontal res and change only the vertical res, and so you can get away with something like 10 resolutions instead of 200+.
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buttersoft
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Re: Why horizontal resolution doesn’t really matter with CRT

Post by buttersoft »

Josh128 wrote:... so you can get away with something like 10 resolutions instead of 200+.
...Which massively speeds up configuration time and also how fast your system can switch resolutions :)

Different Windows updates affect the latter as well.
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matt
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Re: Why horizontal resolution doesn’t really matter with CRT

Post by matt »

The other reason for super resolutions is that some GPUs & DACs are designed to run at a certain pixel clock. This provides a signal that's compatible with a low-rez monitor, while still putting out a high enough resolution for the output device to function properly.

An analog monitor doesn't care whether or not it's getting 1 pixel at a time or 10 duplicate pixels that are the same color - the video signal is the same.
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maxtherabbit
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Re: Why horizontal resolution doesn’t really matter with CRT

Post by maxtherabbit »

nes.og wrote:Interesting, I thought they would appear the same and the reason for super resolutions is to better support multiple 240P console resolutions within one resolution or quicker to switch resolutions with them?
if the "super resolution" is being generated by a computer running emulation software performing pixel repetition then they will in fact look the same
nes.og
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Re: Why horizontal resolution doesn’t really matter with CRT

Post by nes.og »

Thanks for all the responses!

I’m still trying to understand how a monitor handles the horizontal resolution after D to A conversion.

With super resolutions the scan rate is the same and the image is the same but signal is different so there is a bandwidth cap?

If this is correct then what is different about the signal?
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Kez
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Re: Why horizontal resolution doesn’t really matter with CRT

Post by Kez »

The key thing you're missing here, and it's kinda hard to explain without a bunch of diagrams, is that an analogue signal is completely continuous. Imagine a sine wave:
Image

Now this is a digital representation of a sine wave, so it can be broken down to pixels, but a true, real life, analogue sine wave has functionally infinite sampling points. You can pick any two points on that wave, and there will always be another point in between. Digital signals have a finite and predetermined number of "points", and when we convert analogue to digital, the more points you sample, the more accurate to the analogue it will be. You will always be losing information though, because there are infinite points to sample - it's just a case of diminshing returns.

So when we convert a digital signal back to analogue, you are just stitching all those individual points back together into a continuous line, and if your line made of thousands of individual points it will have more detail, but if you're just repeating the same pixels over and over again, the resulting line will be essentially identical whether there is just one red "pixel" or a hundred the line will just be at red for the same amount of time.

As others have said, what determines the limit of horizontal detail on a CRT is the phosphors on the tube itself.
nes.og
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Re: Why horizontal resolution doesn’t really matter with CRT

Post by nes.og »

Thanks for sharing Kez.
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