NTSC and PAL video signals are so complicated I am systematically lost.
My understanding is that, at least for good old monochrome TV signals, the "pixels" exists only vertically, but horizontally the signal is analog which put no limit on the amount of "pixels" send to TV, anything is possible.
Vertically however the resolution certainly is constrained and cannot be chosen.
My understanding is that NTSC have 525 lines interlaced and PAL has 625 lines interlaced, which means a progressive signal should have 263 and 313 lines respectively. Because most systems were designed to be NTSC/PAL without changing the resolution, most PAL systems just send extra dummy lines to fill the gap. And because we take some blanking time, this creates the 240px vertically used by almost all systems. But because overscan was an issue, many system had an option to have 224px, using the top and bottom 8 px as dummy lines (just like the dummy lines of PAL systems), so that we can be sure the entiere surface is visible, and not rendered "inside" the TV.
Is what I wrote above correct ?
Now horizontal resolution is even trickier. If the video signal was black and white there would be no constraint and the signal would be analog (i.e. no limit in resolution). There is still a limit due to the physical analog cables which cannot carry infinite frequencies, obviously, (and that limit is derived from the limit of the RF carrier used in an antenna).
With colour, the analog B/W signal is combined with colour signal of a set frequency, so this becomes an issue when outputing pixels. The horizontal resolution can still be picked up arbitarly, however this will affect the colour artifacts and/or dot crawl. Higher resolution graphics will not follow quick colour changes.
In addition to that, the speed at which pixels are send matters more than the resolution itself. So it would be possible to send 256 pixels horizontally at different rates, and having different ovescan and colour artifacts.
My understanding is that, at least for good old monochrome TV signals, the "pixels" exists only vertically, but horizontally the signal is analog which put no limit on the amount of "pixels" send to TV, anything is possible.
Vertically however the resolution certainly is constrained and cannot be chosen.
My understanding is that NTSC have 525 lines interlaced and PAL has 625 lines interlaced, which means a progressive signal should have 263 and 313 lines respectively. Because most systems were designed to be NTSC/PAL without changing the resolution, most PAL systems just send extra dummy lines to fill the gap. And because we take some blanking time, this creates the 240px vertically used by almost all systems. But because overscan was an issue, many system had an option to have 224px, using the top and bottom 8 px as dummy lines (just like the dummy lines of PAL systems), so that we can be sure the entiere surface is visible, and not rendered "inside" the TV.
Is what I wrote above correct ?
Now horizontal resolution is even trickier. If the video signal was black and white there would be no constraint and the signal would be analog (i.e. no limit in resolution). There is still a limit due to the physical analog cables which cannot carry infinite frequencies, obviously, (and that limit is derived from the limit of the RF carrier used in an antenna).
With colour, the analog B/W signal is combined with colour signal of a set frequency, so this becomes an issue when outputing pixels. The horizontal resolution can still be picked up arbitarly, however this will affect the colour artifacts and/or dot crawl. Higher resolution graphics will not follow quick colour changes.
In addition to that, the speed at which pixels are send matters more than the resolution itself. So it would be possible to send 256 pixels horizontally at different rates, and having different ovescan and colour artifacts.