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Video signal from old game consoles

post #1 of 17
4/28/10 at 11:58am
Thread Starter 
Hi, I'm wondering about the details of the video signal that is output from older NTSC video game consoles like the N64, PS1, and earlier. Some games on these systems are capable of 480i (Tekken 3), but most games appear to only display 240 non-interlacing scan lines. Presumably this is because the graphics processing can't handle more than a 320 x 240 resolution.

So, does anyone know what is done to the NTSC signal to achieve this? I have two ideas: 1) Every other field is simply black - although I suspect the result of that would be video that is too dark and flickery. Or 2) The vertical retrace pulse is tweaked so that the odd & even fields don't interlace, they just overwrite each other. I'm a little skeptical of that option because it seems to break NTSC specification and would increase danger of phosphor burn-in.

Thanks!
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post #2 of 17
4/28/10 at 3:30pm
Quote:
Originally Posted by Tengato View Post

Or 2) The vertical retrace pulse is tweaked so that the odd & even fields don't interlace, they just overwrite each other. I'm a little skeptical of that option because it seems to break NTSC specification and would increase danger of phosphor burn-in.

That's exactly how it works. The Wikipedia article on low-definition television has some information about it:

Quote:


Older video game consoles such as the Nintendo Entertainment System generated a non-standard version of NTSC or PAL in which the two fields did not interlace, and instead were displayed directly on top of each other, keeping the orientation of the scanlines constant. This is equivalent to 240p and 288p respectively. The Video CD format was introduced on such a console (CD-i), and it likewise uses a progressive LDTV signal (352×240 or 352×288), which is half the vertical resolution of SDTV.

In contrast, the NTSC PlayStation was capable of true 480i output, but most games used 240p mode due to limited graphics and CPU power.

More recent game systems tend to use only properly interlaced NTSC or PAL in addition to higher resolution modes, except when running games designed for older, compatible systems in their native modes. The PlayStation 2 generates 240p/288p if a PlayStation game calls for this mode, as do many Virtual Console emulated games on Wii.
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post #3 of 17
4/28/10 at 6:58pm
So what happens to this signal when it is sent to a 1080i CRT? Does it still display progressive or is it now interlaced?
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post #4 of 17
4/29/10 at 2:29am
Quote:
Originally Posted by hoffo View Post

So what happens to this signal when it is sent to a 1080i CRT? Does it still display progressive or is it now interlaced?

My 1080i CRT TV also does native 480p, so 240p signals are simply line-doubled to 480p.
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post #5 of 17
4/29/10 at 4:16am
For the most part, HD displays of any sort treat 240p as 480i, screwing up the progressive nature of the original signal. The result is brighter and far blockier than the original 240p image displayed on an SD CRT.
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post #6 of 17
4/29/10 at 10:43am
Quote:
Originally Posted by darklordjames View Post

For the most part, HD displays of any sort treat 240p as 480i, screwing up the progressive nature of the original signal. The result is brighter and far blockier than the original 240p image displayed on an SD CRT.

Would the 240p signal be scaled to 480i on an SD crt?
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post #7 of 17
4/29/10 at 12:57pm
Quote:
Originally Posted by Jason One View Post

My 1080i CRT TV also does native 480p, so 240p signals are simply line-doubled to 480p.

I have a Toshiba 30HF66 it does 540p but only via component / hdmi when a 480p source is used. So it upscales everything to 1080i over composite / s-video which is the best the old school consoles will do (NES, SNES, N64)
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post #8 of 17
4/29/10 at 1:15pm
Thread Starter 
Interesting, I wonder if any of the 240p games are actually 30-60 fps then? If so, I imagine it would be tricky to upconvert the signal to 480p. Wouldn't most equipment assume it was just 480i and pair the odd & even fields into a single frame to be shown for 1/30th of a sec (resulting in fuzzy motion artifacts)? That's how 480i is converted into 480p60 right?

Or will any displays actually recognize 240p and line double each field(=frame in this case) to get the ideal 480p60 conversion?
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post #9 of 17
4/29/10 at 2:07pm
"Would the 240p signal be scaled to 480i on an SD crt?"

No. The 240 lines are overlaid on top of each other at 60hz, resulting in a 240p image with blank dark lines between those 240 lines. This is what helps the perceived image feel far sharper than 240 lines of resolution would imply.

"Or will any displays actually recognize 240p and line double each field(=frame in this case) to get the ideal 480p60 conversion?"

The preferred option would be if HD displays recognized 240p as 240p and just did the scaling as a 480p image with black lines for every even line. I have yet to hear of an HD display that handles 240p properly though, and the likelihood that one ever will gets slimmer as the days pass. Additionally, a lot of displays get tripped up on 240p over component, not even knowing what to do with the image. A perfect example is Ico on the PS2 hooked up component. Most HD displays go crazy with this.
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post #10 of 17
4/29/10 at 6:27pm
Quote:
Originally Posted by darklordjames View Post

"Would the 240p signal be scaled to 480i on an SD crt?"

No. The 240 lines are overlaid on top of each other at 60hz, resulting in a 240p image with blank dark lines between those 240 lines. This is what helps the perceived image feel far sharper than 240 lines of resolution would imply.

scanlines are exactly what I'm looking for, especially in older games, so I'm definitely looking for an SD CRT then.
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post #11 of 17
4/30/10 at 6:23am
[quote=darklordjames;Additionally, a lot of displays get tripped up on 240p over component, not even knowing what to do with the image. A perfect example is Ico on the PS2 hooked up component. Most HD displays go crazy with this.[/QUOTE]

Yes, I have my PS2 connected to a 37" Olevia via component and PS1 games don't show any video at all (although you can hear the game). But when I connect it to my Sony LCD projection tv via component, I have no problems with the video for PS1 games.

Does anyone have any idea why there is a difference (besides the fact the tv and PS2 are both Sony products)?
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post #12 of 17
4/30/10 at 2:08pm
It's just a common scaler problem.
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post #13 of 17
5/6/10 at 11:03am
I have this issue when I run these systems into my Onkyo 667 and then passed through HDMI to the TV(Panasonic TH50PZ80U). I get flashes of the game and audio. I bypassed the receiver and went straight to the TV and it takes care of the scaling. I haven't noticed any issues when connected to my set this way.
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post #14 of 17
5/16/10 at 5:23pm
It is precisely because of the nature of low-definition gaming that I decided to get a nice flat-screen Sony SDTV with component inputs to complement my Sony KD-30XS955 CRT HDTV.

Because my HDTV line-doubles 240p signals, sprites look much blockier and uglier than on an SDTV with proper scanlines, and 3D polygons are a nightmare. In other words, it doesn't even try to properly upscale. It just doubles each line and calls it a day, and it looks bad. As a result, anything older than the Dreamcast looks like absolute ass on it, including PS1 games played on the PS2 through component.

As such, I have my NES, SNES, N64, and Atari on the SD set, and my PS2, Wii, and 360 on the HD set. That way, everything looks great. Although I'm considering moving the PS2 to the SD set, as few of my games even use 480p, and PS1 games would look like they should, so...
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post #15 of 17
5/18/10 at 8:16pm
DarkZero24, you are in the exact same situation I'm in. If I may ask, what flat screen CRT did you buy? I've been scouring craigslist to find a good geometry CRT TV and I STILL haven't found one yet. I just checked a 27fs120 but it always has the geometry tilted wrong and bowed real bad on the top and bottom edges. Did you find a set that you found to be adequate? I was playing a PS1 game on a PS2 system via component.

Funny thing is I have a KD-34XS955 for TV in the bedroom and a Philips 42" LCD for PS3 and Wii so I almost have the exact same TVs you have. lol.
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post #16 of 17
5/19/10 at 6:43am
So If I'm going to be playing SNES/PS1/PS2 games (480i) via component connection would you rather have a KV-27HS420 or KD-27FS170. I have to decide between these two sets. Would their be artifacts or any problems playing 480i content on the HS420?

Thanks guys!
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post #17 of 17
5/20/10 at 12:12pm
SNES and PS1 are actually 240p for almost all ingame graphics. PS2 is 480i but there is a program called GSM that will force 480p output.

If going for a easy approach get a TV that supports S-Video for SNES and PS1 and Component for PS2 and is 4:3. But if you wanna be a baller get RGB outputs for the consoles and get a TV (or monitor) that will accept RGB.

Personally I would get a Sony PVM model monitor.
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