Tron and Tapper were at 30Hz????

[whammoed]

Noticed recently that Tron and Tapper had resolutions of 512x480 at 30Hz.  Does this mean that they were interlaced on a Standard Res monitor to get that high resolution.  If so, I don't remember, did it have a lot of flicker??  Also, if this was the case, would there be a reason to not run it non-interlaced on a d9200??

im confused

[Hoagie_one]

i seem to remember tron being kinda flickery, but tapper was always smooth

[RayB]

I believe they used what's called a "medium" resolution monitor, rather than the "standard" (CGA) resolution. That's why they look nice and sharp.

Also nice n crispy are:

Timber
Demolition Derby
Narc

From Atari:
Marble Madness
Paperboy
Super Sprint/Championship Sprint
Toobin
...

[spyhunter]

Narc was Medium, however the other Midway games mentioned are listed as Standard Resolution on www.klov.com.

I'm trying to figure out this whole 30Hz thing for my Spy Hunter, which is the same way, to work with it's newly installed LCD and I'm still confused.

I spoke to a techy at Happ Controls today and he told me some mumbo jumbo about needing to use a CRT yoke and that it has a need to be placed the correct way, and because of this an LCD would never work, but I still think it lies with this 30Hz thing...

SH

[ahofle]

Yes they are interlaced.  Flicker only shows up when you have horizontal lines of high contrast difference sitting right next to each other (Windows has lots of 1 pixel lines like this which is why an interlaced Windows desktop looks like crap).  This is of course because every other line is drawn at a time.  Here's a quote from wpcmame who knows more about this stuff:

Flicker is only visible if there is a contrast difference in alternate lines.
If a low-res arcade game is double-sized, the odd and even lines are exactly the same and there is no flicker.

Several arcade games (e.g. tapper and popeye) originally used interlaced display and didn't flicker (except where  intentional like the popeye bee-nest)

Spy Hunter is another interlaced game that never flickered.  I honestly don't see how an LCD (which does not 'interlace') could ever support a game like this, but what do I know. 

[spyhunter]

Hey guys, any new ideas?  Thanks!  There's gotta be a way to get these Midway games to display on something other than their original CRTs, I refuse to believe that they are CRT exclusive.  The installed LCD in my game is just too sweet to give up only to go back to the dinosaur of a CRT that was in it.

I've since tried this rgb to vga converter which is essentially the same thing built into the LCD and no change:

http://www.ambery.com/rgbcgatovgac.html

What device could double the 30Hz refresh rate to 60Hz in order to use a more modern display??

SH

[ahofle]

Just curious, why did you buy a $450 untested LCD for your Spy Hunter when you could've just gotten a 19" arcade monitor for under $200?

[SavannahLion]

Flicker is only visible if there is a contrast difference in alternate lines.
If a low-res arcade game is double-sized, the odd and even lines are exactly the same and there is no flicker.

Score one for the CRT team. Why didn't anyone dig up that information when the stupid CRT vs LCD debate was going on?

What device could double the 30Hz refresh rate to 60Hz in order to use a more modern display??

It's a line doubler or scanline doubler. Kind of expensive unless you can locate the parts to build your own. 60Hz? Except for ultra-new monitors, most every one I've seen supprt as low as 30Hz.

[MonMotha]

When you start dealing with interlace, the concept of "frame rate" gets a bit muddied.  There are three things to consider:

1) The rate at which vertical sync is asserted to the monitor - this is the "field rate", or the rate at which every half of the interlaced frame (known as a field, consisting of every other line) is updated
2) The video frame rate - this is half the field rate, or the rate at which the entire display gets updated on the monitor
3) The graphics update rate - this is the rate at which the game updates the framebuffer from which the video is generated.  This can be anything the game wants, but is usually an integer (often power of 2) divisor of the field rate, with the frame rate being popular, for several reasons.  This need not be equal to the frame rate even on progressive video.

TVs (both NTSC and PAL) use interlaced scanning to achieve higher resolution in a small amount of RF bandwidth.  The downside is that you only get half the picture at a time.  However, on TV the rate at which the picture is updated is once per field, not frame.  Many computer games only updated the graphics frame once per progressive frame, in order to prevent tearing, but scanned out interlaced for compatibility with TVs (and standard resolution arcade monitors).  This eliminates graphical artifacts (mostly tearing) due to the interlace scan, but also makes the video appear kinda choppy.  With some care, the graphics can be updated once per field, but then you have to watch out for tearing.

You can really see this all going on with Dance Dance Revolution if you compare 4th Mix (or older) and 5th Mix through Extreme.  The monitor is standard res.  Old versions ran a 480 line (roughly) framebuffer and scanned it out interlaced, but only updated every full frame.  The monitor didn't flicker (30Hz monitor flicker is EXTREMELY noticible and quite objectionable), but the graphics were pretty choppy due to the slow update rate.  5th Mix and newer update the framebuffer every field.  The graphics are a lot smoother in motion now, but on horizontal motion, you can notice some tearing due to the interlace.

Many arcade games simply ran ~240 line progressive video at 60Hz to get standard resolution compatible timings.  480 lines on a standard res monitor is possible per the above, but seemingly "odd" things crop up due to the interlace.

Personally, I think interlace is a dirty hack and needs to go away, but we're stuck with it on ATSC due to the popularity of 1080i.

Now, this is where your 30Hz comes from.  I'm guessing that the monitor is still refreshed at 60Hz, but the framebuffer is only updated at 30Hz, resulting in choppy graphics.  Games which update their framebuffer at 60Hz won't exhibit choppy graphics, but if you watch for tearing on horizontal motion, you'll probably see some.

Of course, now that VGA monitors are reasonably common in arcades, you see plenty of games running ~480 line progressive scan, which looks pretty darned nice.

I'm not saying any of this applies to Tron or Tapper (I have no idea), but it's something to bear in mind.

[DaveMMR]

Score one for the CRT team. Why didn't anyone dig up that information when the stupid CRT vs LCD debate was going on?

Because it would have been "debunked" by half-truths and nonsense. 

[spyhunter]

There are many reasons to go with LCD such as less weight, less space, less deathly, less power, less high-pitched sound, instant on, brighter crisper display.  I'm sure there are even more, and that's worth a few hundred $$ more, IF it would only work...

I didn't think for a second that modern technology such as LCD would not be able display whatever a CRT can, but I should have...

SH