• Synthead
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    11 months ago

    In general, what is the highest frequency that can be carried over a wire?

    I know it can do these resolutions in practice because I have personally operated CRTs at 4000x3000 resolution in the early 2000s. This could be considered “the 4:3 of 4K.” It was not done on fancy equipment or high-end monitors. Analog stuff really could just go to really high resolutions and refresh rates with above-average, but typical stuff.

    CRTs simply respond to waveforms for red, green, blue, vertical sync, and horizonal sync. That’s it. If you want more horizonal pixels, make your scan lines denser. If you want more vertical pixels, add more scan lines. Want a faster refresh rate? Simply run all the signals faster.

    There is no hard upper limit to it. With digital signals, there are throughput limits per spec due to bit rates, but with analog, there are no bits. Resolutions like 40k x 30k are theoretically possible. The difficult parts are rendering the signal at these high frequencies, and being able to meaningfully display them. The VGA connection itself has no limits.

    • Aux@lemmy.world
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      11 months ago

      In theory you can push anything over the wires, be it analogue or digital. The issue is with communication standards. VGA defines which wires should be used, which frequencies should be used, etc. Thus VGA specifically has limitations. Otherwise monitors, cables and video cards would have compatibility issues. I don’t think you were pushing 4000x3000 resolution through VGA. Just like today no one is pushing video streams to giant building sized screens over consumer HDMI or DVI.

      Another example is XLR VS 3.5mm jack. In theory you can push audio signal of any quality over both, but XLR by spec is balanced and shielded, while 3.5mm is not. This means that XLR is capable of pushing much better audio.

      • Synthead
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        11 months ago

        Otherwise monitors, cables and video cards would have compatibility issues.

        You’re right, and this was absolutely a thing. Video cards could produce whatever they were capable of, and monitors could display whatever they were also capable of. You could also push resolutions and refresh rates to monitors that was beyond the monitors’ specs, and you would also risk damaging the monitor by doing this.

        I don’t think you were pushing 4000x3000 resolution through VGA.

        You don’t need to believe me. That’s your choice. I had friends that could do the same. This was with a Matrox card and a 21" Acer CRT. The display was nearly impossible to read, and the color mask broke up the individual pixels too much, anyway.

        Just like today no one is pushing video streams to giant building sized screens over consumer HDMI or DVI.

        Digital video has upper limits in its specs. This is the whole point of this conversation.

        Another example is XLR VS 3.5mm jack. In theory you can push audio signal of any quality over both, but XLR by spec is balanced and shielded, while 3.5mm is not. This means that XLR is capable of pushing much better audio.

        A bit of incorrect information here. There is no “unshielded 3.5mm spec.” Good cables have shields, but not all. XLR doesn’t have the ability to transport higher frequencies because it’s balanced, or “much better audio.” On paper, unbalanced audio is better for short runs because there is more opportunity for XLR signals to have extremely minute signal quality issues due to the hot and cold signal mirroring, but it’s so small that it doesn’t matter.