tetsuo55 wrote:creaothceann wrote:tetsuo55 wrote:I think we can all agree that the CRT-TV's the snes was designed for was completely unable to display a progressive signal.
although the snes internally computes a certain height the full signal will eventually be 525 lines high. Unlike interlaced both frames simply display the same image.(effictively creating a 30 fps progressive image on a 60fps screen by line doubling)
Let's recap:
The TV draws 525 lines interlaced in two passes at 60 fields per second / 30 frames per second. The signal source is responsible for shifting every other field.
The SNES doesn't shift the fields in "progressive mode", so we get a 60 Hz progressive image with 525 / 2 visible lines, and black scanlines between them. In "interlaced mode" the SNES includes the shifting signals, so we get a 30 Hz interlaced image with 525 visible lines and no (or less pronounced) scanlines.
Aspect ratio can be safely assumed to be 4:3. Let's drop that already.
That sounds very plausible
Again confirming that the picture height is 486..
We are not discussing the 4:3 picture aspect ratio but the 1.16.... pixel aspect ratio
tetsuo55 wrote:Gil_Hamilton wrote:
Except that scan position is controlled by the system.
As I understand things, ye olde systems muck with the timing signal to get the same set of scanlines drawn twice. It confuses the hell out of modern panel TVs, but works GREAT on CRTs.
And you may notice that the dark scanlines disappear(or at least shrink) when the system is in "high-res" mode. Because it's now drawing picture inside the black lines.
The result is the same, the image is twice as high
the question is how does it work exactly?
I like how you respond to posts detailing why you're totally and 100% wrong with a brief inanity about how it confirms you're right.
You clearly either didn't read what was said, or chose to ignore it.
525/2=262.5, but you don't get a half scanline. If you accept what creaothceann posted, you must accept that the SNES outputs a 60FPS image that's less than 486 lines tall(in fact, it's 224 lines tall).
Odd and even frames on a real TV have differing scanline counts. To make sure the scan is interlaced, actually. If they have the same number of lines, TVs would tend to drop them on the same set of lines, giving you a half-resolution progressive signal.
Fact: The original NTSC development committee KNEW that their standard was easily forced into progressive scan, and that TVs would merrily plow ahead that way.
Certainly hardware has changed since then, but the fundamental behavior of a CRT TV now isn't a lot different than it was then.
The TV DOES NOT draw all the scanlines all the time. It only draws enough lines to get the resolution the source is trying for. If it DID draw all the lines, the signal would be in proper NTSC spec, and work just as well as a fancy-pants PS2 video feed on a panel TV.
There is, in fact, a good bit of dis-satisfaction among a certain segment of the market about the fact that modern ports of older games use 480i instead of the so-called 240p, which all but eliminates scanlines from the image(and creates a few artifacts).
Under your flawed hypothesis, they're ALL 480i, so there's no difference. But the difference IS there, and IS visible.
http://scanlines.hazard-city.de/ has some decent samples of the difference.
Another test: Go fire up something with a reasonably fast horizontal scroll. Now look for the fringing that occurs on horizontal scrolls because both sets of scanlines are at different locations. You won't see it. Because the second set of scanlines isn't illuminated.
And again, I ask you to check some actual software, such as Secret of Mana, that uses the "high-res" mode. The introduction of the second scanline set is highly visible, both in terms of scanline reduction and in terms of the flicker introduced.
But what do I know? I'm clearly a complete buffoon, since I don't understand that NTSC = DVD. And I subscribe tot he silly belief that the NTSC spec placed the scan controls within the video signal, making it very easy to convince a TV to display non-spec images.
