Comment by ssl-3

> which is how physical dot/pixel/phosphor/mask/whatever patterns have anything to do with frame sizes of a digital video format,

In that context, the answer is: They don't really have any relationship at all.

Plenty of TVs of the past (from any continent) also had no physical dots/pixels/patterns at all. These were monochrome, aka black and white. :)

They had an inflexible number of lines that could be displayed per field, but there was no inherent delineation within each line as to what a pixel meant. It was just a very analog electron beam that energized a consistently-coated phosphorescent screen with a continuously-variable intensity as it scanned across for each raster line.

Pixels didn't really happen until digital sources also happened. A video game system (like an Atari or NES, say) definitely seeks to deliver pixels at its video output, and so does a digital format like DVD.

But the TV doesn't know the difference. It doesn't know that it's displaying something that represents pixels instead of a closed-circuit feed from a completely-analog pixel-free tube-based camera.

The "non-square pixel" part is just a practical description: When we have a digital framebuffer (as we do with a DVD player), that framebuffer has defined horizontal and vertical boundaries -- and a grid of pixels within those boundaries -- because that's just how digital things be.

When we smoosh the pixels of a DVD player's 720x480 framebuffer into an analog display with an aspect ratio of 4x3, we wind up with a combined system, with pixels, and those pixels aren't square.

---

And that's perfectly OK, though it does lead to weirdness.

For example: To produce a display of a perfect square that is 100 lines high using a 4x3 NTSC DVD is actually impossible. It'd have to be 100 pixels high and 112.5 pixels wide, which we can't accomplish since the format doesn't have that kind of precision. It's impossible with an LCD, and it's impossible with an analog set from 1955 just the same.

It's a DVD limitation, not a display limit. There's no great trick to producing a perfect square with analog gear, where pixels aren't a thing -- but we can't get there with the DVD's non-square pixels.

That weirdness doesn't have anything at all to do with how the display is constructed, though: Again, the TV has no concept of what a pixel even is (and a shadow mask doesn't necessarily exist at all).