eli5: how does vga, dvi,hdmi, displayport,usb control each pixel of a monitor if the cable doesn’t seem to have a wire for each and every pixel?
In: Technology
There are two techniques in use. Firstly the screen contains a big serial to parallel converter. This is a device that is as long as there are pixels in a row with multiple latches one after the other. The input is connected to the first latch and when the input signal goes low it sends a signal to the latches to pass the value in it on to the next latch. When the signal gets to the end there is a V-sync signal from the source which tells all the latches to output it signal on its own line. This way one input signal turns to hundreds of output signals.
Each of these is again connected to every pixel in a column. There are similar wires for each row. But a pixel only lights up if its row and column wire is powered. First only the top row is powered. When the V-sync signal is sent the first row is powered off and the next row is powered on. It does this all the way down when the input sends an H-sync signal to reset it to the first row again.
I am of course simplifying things a bit here. For color you need to do all this three times. Detecting the sync signals is also a topic on its own. The signal is also not digital so you can actually get the multiple color gradients. Different screen technology need different types of signal as well. And so on. What I describe is pretty accurate for VGA, you even have separate V-sync and H-sync wires. DVI and HDMI is the same standard with different connectors and is a digital form of VGA but other then that the signaling is the same, except that all the sync signals is put together on one single line. DisplayPort and USB on the other hand use more traditional packet systems to deliver the data which then involves a lot of data processing to turn it into what is basically a VGA signal for the display itself.
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