interlacing - NESdev BBS

interlacing
by evildragon on 2007-04-30 (#23786)

ok, this is for a real project...

does the NES PPU support interlacing at all? if so, does it actually increase the vertical pixels, or just double them?

(and how is it triggered)

by kyuusaku on 2007-04-30 (#23790)

No, it does not support interlacing. If it did and it redrew each line, would that make any sense?

by Bregalad on 2007-04-30 (#23791)

Yeah, I already asked this question here, and the answer was no.
You cannot get anything else than 256x240.

by evildragon on 2007-04-30 (#23794)

kyuusaku wrote:
No, it does not support interlacing. If it did and it redrew each line, would that make any sense?
yes, that makes sense, that's what i'd call double pixeled..

by kyuusaku on 2007-04-30 (#23795)

My question to you is why would they waste money on memory to store a line for the next field to achieve half the performance?

by evildragon on 2007-04-30 (#23797)

kyuusaku wrote:
My question to you is why would they waste money on memory to store a line for the next field to achieve half the performance?

for a still screen, like a map to a level, it could help.. for 2D games, it is a waste...

by doppelganger on 2007-04-30 (#23813)

It's a waste to have more than 120 pixels for vertical resolution?

Exactly how is this?

by evildragon on 2007-04-30 (#23817)

doppelganger wrote:
It's a waste to have more than 120 pixels for vertical resolution?

Exactly how is this?

it would be a waste for performance.. for most side scrollers, you don't even need the extra pixels...

if it's a map screen, like in zelda, then those extra pixels could help...

by dvdmth on 2007-04-30 (#23820)

How many SNES games used the S-PPU's interlace mode?

by evildragon on 2007-04-30 (#23821)

dvdmth wrote:
How many SNES games used the S-PPU's interlace mode?

i remember atleast one game using the pseudo high-res mode.. (though not interlaced)

by blargg on 2007-04-30 (#23823)

Since the method used by the NES to display a progressive (non-interlaced) signal is probably not standard, some video devices always display the signal interlaced. Examples include new-fangled high-definition TVs and PC video capture cards. A NES connected to one of these could be made to display an interlaced image if the user helped the NES determine which was the even field. To do the actual image display, you'd most likely switch between two different sets of tiles, one for even lines and the other for odd lines. This is simple if you are using banked CHR ROM (MMC3 etc.).

by kyuusaku on 2007-04-30 (#23827)

evildragon wrote:
kyuusaku wrote:
My question to you is why would they waste money on memory to store a line for the next field to achieve half the performance?

for a still screen, like a map to a level, it could help.. for 2D games, it is a waste...

If field B contains the same lines as field A, all that would do is reduce the frame rate by half and shimmer the screen in an annoying way. As people have pointed out, you need twice the memory to achieve twice the lines!

by evildragon on 2007-04-30 (#23832)

kyuusaku wrote:
evildragon wrote:
kyuusaku wrote:
My question to you is why would they waste money on memory to store a line for the next field to achieve half the performance?

for a still screen, like a map to a level, it could help.. for 2D games, it is a waste...

If field B contains the same lines as field A, all that would do is reduce the frame rate by half and shimmer the screen in an annoying way. As people have pointed out, you need twice the memory to achieve twice the lines!

i know that, but you can also switch between lines.. each frame, it could alternate between "virtual fields" (for a lack of a better term)..

I've done that on a Sega 32X, which doesn't even support interlacing, and it worked.. it's ehh, hard to describe, but the person above you did it better than i said it..

by kyuusaku on 2007-04-30 (#23836)

You could fake a 480 line display if the NES would output interlaced video, but it doesn't. What blargg described relies on a display to misinterpret the NES' video.

Quote:
I've done that on a Sega 32X, which doesn't even support interlacing, and it worked.. it's ehh, hard to describe, but the person above you did it better than i said it..

If the 32X doesn't output interlaced video, you can't "do it"... Are you serious or just BSing again?

by evildragon on 2007-05-01 (#23842)

kyuusaku wrote:
You could fake a 480 line display if the NES would output interlaced video, but it doesn't. What blargg described relies on a display to misinterpret the NES' video.

Quote:
I've done that on a Sega 32X, which doesn't even support interlacing, and it worked.. it's ehh, hard to describe, but the person above you did it better than i said it..

If the 32X doesn't output interlaced video, you can't "do it"... Are you serious or just BSing again?

i said i was done hoaxing.. let me explain how the 32X works...

The 32X is not capable of generating it's own sync. It uses the Genesis video sync signals (and it's RGB lines too)... With that in mind, you can trigger the Genesis VDP to do interlaced mode (either one of the two, won't matter here), and on the 32X, have it "flicker" between virtual fields.. For example, if you forced a 480i display into 240p, it would look funky, like each frame is alternating.. do this on the 32X frame buffer and your set, as the Genesis is doing the interlacing for the 32X..

This was never done on games, and not recommended by Sega, because the 32X could lose a frame, then the fields became backwards.. (odd to even, and even to odd)

by evildragon on 2007-05-01 (#23844)

here's an example of what im trying to explain..

a technique like this:

this could work...

with that, you could reconstruct a full vertical 480 pixel image (though, an upscaled horizontal 320 pixel image to 640)

http://blackevilweredragon.spymac.com/intfull.jpg

by tepples on 2007-05-01 (#23857)

But it would only work on those few TVs that treat the NES's 240p signal as 480i. Most of these are digital EDTVs and HDTVs that have a built-in upscaler.

by evildragon on 2007-05-01 (#23860)

tepples wrote:
But it would only work on those few TVs that treat the NES's 240p signal as 480i. Most of these are digital EDTVs and HDTVs that have a built-in upscaler.
that's true, that's why i asked if there's an interlacing mode, at all on the NES...

i use an HDTV, so i tend to take it for granted, in fooling it's upscaler..

by Bregalad on 2007-05-01 (#23862)

Quote:
that's true, that's why i asked if there's an interlacing mode, at all on the NES...

Again, that is exactly what I asked in the older thread I linked above, and there was a clear negative answer already made.
I assume we're not supposed to tell you one million times the NES cannot interlace. You can do some dithering tough. This doccument explains an intersting concept to get more colors.

by evildragon on 2007-05-01 (#23864)

Bregalad wrote:
Quote:
that's true, that's why i asked if there's an interlacing mode, at all on the NES...

Again, that is exactly what I asked in the older thread I linked above, and there was a clear negative answer already made.
I assume we're not supposed to tell you one million times the NES cannot interlace. You can do some dithering tough. This doccument explains an intersting concept to get more colors.
no, you don't have to tell me a million times, and im not really asking a million times.. the topic got changed to proving how the 32X in theory could interlace.. (and how if a video device treated 240p as 480i), the NES then could in theory do the same..

by tepples on 2007-05-01 (#23865)

The Sega Genesis video chip has an interlaced mode. Sonic the Hedgehog 2 used it for multiplayer mode.

by evildragon on 2007-05-01 (#23866)

tepples wrote:
The Sega Genesis video chip has an interlaced mode. Sonic the Hedgehog 2 used it for multiplayer mode.
i know, but the 32X itself can't interlace...

my theory (and it has been tried too once, so it's not a theory anymore), aided in 32X doing interlaced video...

by tepples on 2007-05-01 (#23869)

The 32X genlocked its own video to that of the Genesis. (Evidence: Some 32X games used the Genesis PPU for the backgrounds and the 32X PPU for sprites.) Perhaps if the Genesis PPU was in 480i mode, the 32X would offset every other field down by a half scanline, giving the effect you seek.

But the NES, on the other hand, can't genlock to any 480i source.

by evildragon on 2007-05-01 (#23870)

tepples wrote:
The 32X genlocked its own video to that of the Genesis. (Evidence: Some 32X games used the Genesis PPU for the backgrounds and the 32X PPU for sprites.) Perhaps if the Genesis PPU was in 480i mode, the 32X would offset every other field down by a half scanline, giving the effect you seek.

But the NES, on the other hand, can't genlock to any 480i source.
i know that... Doom: 3D graphics done by the 32X.. Text, and HUD done by the Genesis VDP.. i said i've already done this, it works for the 32X...

i think this thread is done, it's already been said the NES can't address any interlaced mode.. but doing this on an HDTV would be pretty cool...