> On May 20, 2024, at 1:37 PM, Wayne S via cctalk <[email protected]> wrote:
>
> Young , hah. No i’m old 70.
> The pc monitors, not Tv, always had a setup menu. Even the Vt100 series let
> you choose interlace if you needed.
VT100? I don't think so. And yes, it has a setup menu, but that's setup of
the terminal functionality, not the monitor part.
The earliest monitors could only handle one format. A major innovation was
"multisync" where the monitor would determine the horizontal and vertical sweep
rate and line count, and display things the right way. The first PC I owned
had one of those, and as far as I can remember it had nothing that one would
call a "setup menu".
The reason interlace matters is not the very slight slope of the scan line in
analog monitors, but rather the fact that alternate frames are offset by half
the line spacing of the basic frame, so each frame sweeps out the gaps in
between the lines scanned by the preceding frame. It matters to get that
right, otherwise you're not correctly displaying consecutive rows of pixels.
In particular, when doing scan conversion (from analog format to a digital X/Y
pixel raster) you have to offset Y by one every other frame if interlace is
used, but not if it isn't.
paul
