Do old 15Khz Arcade CRT monitors have only 240 vertical line

[NoAffinity]

Nintendo cabs of that era (donkey kong, popeye, Dk jr etc) are sanyo 20ez's. Definitely not 480i.

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[nes.og]

The other games you mentioned were 240P and used the same monitor but Nintendo choose to program and display Popeye at 512 x 448 interlaced. If you do a search you will find this information in many places on the web including the Wikipedia page for the arcade game. If I discovered this before then I wouldn’t have posed the question on this thread.

[Bassa-Bassa]

There are some other arcade games from the 80s aside of Popeye meant to be displayed with interlaced scan, check Midway stuff (Spy Hunter, for example). Those surely could be used on monitors which weren't able of an interlaced display, they just would flicker a lot (although many elements weren't actually drawn in high resolution, so it'd be only half-bad). Anyway, the cases of 15khz monitors unable of 480i should be extremely rare and for silly reasons, as it was explained to you, 240p and 480i are technologically the same thing and that counts for both: TVs and arcade monitors.


Edit: Also, the "lines" which are 240 (or 480) are indeed "horizontal".

[Xer Xian]

The most in-depth discussion of scan lines you will find - anywhere

.. thanks to which you will understand why the interlacing effect needs the half-line (horizontal) offset every other field. The (active) scan lines were actually slightly tilted, so varying the starting point by half a line for each field automatically yields interlacing:

Another reference is here (second reply).

[Sumez]

So you are saying the arcade CRTs were also interlaced with the same amount of lines and displayed 240P using the same technique (Repeatedly just displaying one interlaced fields and skipping the other)

Yes, the exact same technique is used. You can send the video signal of an arcade PCB directly to most consumer TVs via its RGB input and they'll display it completely fine without further modifications - that's what most superguns do (well, basically - you'll want some resistors and stuff, but that has nothing to do with how 240p works).

I'm probably just repeating what everyone else is saying, but "skipping the other field" is somewhat misleading terminology, since the technology displaying the image doesn't have an actual "field" that's being skipped, that's merely how the viewer perceives it. The CRT just has a beam that's drawing a continuous line so to speak.

[Bassa-Bassa]

He'll surely understand it when figuring out where the "double strike" term he likes comes from: one physical line on the screen is "struck" twice with the same content.

[Sumez]

For what it's worth, this is the first time I've heard that term

[Fudoh]

@Bassa-Bassa: that's wrong. Why would a line be showing the same content for two consecutive frames? There's no reason why two adjacent frames on a 240p signal should be identical.

[Bassa-Bassa]

My mistake. I think I have my brain too focused on the double scan method for 240p content on 31khz monitors these days. I'm so sorry.

[nes.og]

Thanks for all the info guys, this a a great community!

I know the lines run horizontally but are counted vertically. I should have been saying “Vertical Resolution” instead so my bad.

NES Developers used the term “Double Strike” to refer to how the 240 vertical resolution video was output to be displayed on just the odd lines repeatedly for 240P 60fps opposed to designing the games at 480 vertical resolution to be displayed alternating between the odd and even lines for 480i 30fps.

[nes.og]

Just saw your post on the previous page Unseen. Some how I skipped over it before, thanks for your input. You seem to be describing the same thing as HD RetroVision but with some more detail provided.

I meant to say fields instead of frames earlier.

[NoAffinity]

The other games you mentioned were 240P and used the same monitor but Nintendo choose to program and display Popeye at 512 x 448 interlaced. If you do a search you will find this information in many places on the web including the Wikipedia page for the arcade game. If I discovered this before then I wouldn’t have posed the question on this thread.

I stand corrected. Please forgive my naivete.

[nes.og]

The other games you mentioned were 240P and used the same monitor but Nintendo choose to program and display Popeye at 512 x 448 interlaced. If you do a search you will find this information in many places on the web including the Wikipedia page for the arcade game. If I discovered this before then I wouldn’t have posed the question on this thread.

I stand corrected. Please forgive my naivete.

Hey, I’m the one that asked if 15Khz 240P arcade games displayed 240P in a different manor then 15KHz TVs LOL

[Josh128]

Currently running an Ultimarc MAME system on my Mace cab using a k7000 monitor (probably the most ubiquitous 25" arcade monitor of all time) and it displays fine 480i in Windows desktop or any MAME games that run higher than 15KHz resolutions.

Also, my 27" Wei-ya Tri-sync can run 480i-- and if you adjust the geometry correctly, its one of the finest native 480i signals Ive ever seen, almost looks progressive.

Thanks for sharing, that’s awesome that you own a K7000. It is one of the monitors that made me think that some may just have 240 lines total because that is what the specs note in the user manual. I now know that they were just referring to progressive scan opposed to interlaced. Upon doing further research I believe that the K7000 was used at 480i for Nintendo’s Popeye.

So are you saying you can run 480P 31KHz games at 480i and they still look fine without flicker?

Well, the Tri-sync is capable of 480p/31KHz so theres no need to run them at 480i, but yeah, the 480i looks very close to 480p on it, especially in stills. In moving graphics you can still tell its 480i, but still looks very good.

[nes.og]

Well, the Tri-sync is capable of 480p/31KHz so theres no need to run them at 480i, but yeah, the 480i looks very close to 480p on it, especially in stills. In moving graphics you can still tell its 480i, but still looks very good.

I totally glossed over that you mentioned that. My goal is eventually have a tri sync cab with MAME. I know you can try to emulate the look of 15Khz games at 31KHz but it’s not the same.