Best option for rotating vertical-only arcade games on CRT?

[sofakng]

I've built a custom arcade cabinet that uses a 27" CRT TV. However, I've recently become interested in MiSTer (and obtaining game PCBs, etc) but a lot of games (especially SHMUPS) are vertical-only and require physically rotating the CRT monitor.

What option(s) are available that don't require physically rotating it? I also don't have room for a second arcade cabinet.

Are there any external scaler/rotation devices with extremely minimal lag?

If I replace the CRT with an LCD does that make it easier (ie. better quality/resolution with rotation) ? The other problem is that my cabinet is built for a 4:3 display and it's very hard/impossible to find a 27" 4:3 LCD.

Thanks for any advice!

[nmalinoski]

What option(s) are available that don't require physically rotating it? I also don't have room for a second arcade cabinet.

Honestly, unless the game has a built-in rotation option, I don't think there is any other option other than rotating the display. I know some candy cabs had a rotation mechanism that still required you to do some disassembly to do the rotation, but you didn't have to bear the entire weight of the display yourself. Since you're asking, you likely don't have one of those mechanisms.

Are there any external scaler/rotation devices with extremely minimal lag?

The most minimum of lag you're going to get is 1 frame, because the video processor needs to completely cache an entire frame before it can rotate it and start reading it out sideways.

Frames are drawn left to right, top to bottom. To do rotation, you need the frame to be drawn top to bottom, left to right (or bottom to top, right to left); basically, instead of outputting rows of pixels, it needs to output columns, and a video processor would have to wait until the last line of the frame is received before it can start outputting that first column.

[orange808]

I know some candy cabs had a rotation mechanism that still required you to do some disassembly to do the rotation, but you didn't have to bear the entire weight of the display yourself.

Doesn't have to be a candy cab.

https://usermanual.wiki/Document/TaitoG ... 96656/html

The most minimum of lag you're going to get is 1 frame, because the video processor needs to completely cache an entire frame before it can rotate it and start reading it out sideways.

Unfortunately, I don't know of any machines that do rotation and output 480i.

[Fudoh]

I guess the easiest way today, both in terms of setup and cost would be a Dido Jr. in combination with an Extron VSC. The Dido will rotate your image and the Extron will turn it into 480i. The VSC also gives you sizing and centering controls outside the monitor chassis.

[nmalinoski]

The most minimum of lag you're going to get is 1 frame, because the video processor needs to completely cache an entire frame before it can rotate it and start reading it out sideways.

Unfortunately, I don't know of any machines that do rotation and output 480i.

Don't the TVone Corio 2 scalers do both?

[Fudoh]

yes, but those don't fall into the "easy setup" category. And neither are they cheap these days.

For stuff running on MiSTer you don't need an external rotation device. If you utilize the MiSTer's HDMI output, you can rotate and scale the game right there. Then you just need a cheap HDMI to VGA dongle and an Extron VSC machine from ebay.

Rotating genuine 15khz sources like PCBs is more complicated. Here you need a processor up front that will at least line double your output, then on to your rotation device and re-interlacing as a final step.

[orange808]

Don't the TVone Corio 2 scalers do both?

No. The Corio2 can't do rotation. It only mirrors or flips the image. No pi/2 rotation.

The Corio 3 is the only "unknown" possibility I can suggest--and I don't know if it would work. It's possible, but I don't want to explore it. That would be an expensive experiment.

I don't know if the custom output resolution option is still available on the Corio3. It is built for digital signage, so the custom output feature exists to drive various video walls--using progressive signals. It may or may not do 480i. Also, if I remember correctly, the firmware abandoned frame lock years ago.

Fudoh has the best suggestion. It will introduce quite a bit of lag, but that's unavoidable. Both external machines will need frame buffers to do their jobs. The Dido Jr and the Extron VSC both do frame rate conversion. You'll want to dial the Dido Jr refresh as close to standard NTSC as possible. Otherwise, you'll get frame rate "judder" from the Dido Jr and the Extron. You don't want to convert 54Hz to 60Hz with the Dido Jr and convert 60Hz to 59.94Hz with the Extron VSC.

There's only one really good solution: build a cab with a rotation option.

[sofakng]

Thanks so much for the suggestions!

What's the main problem with rotating these games? Why does it require converting to 480i?

For example, DoDonPachi supposedly has a resolution of 240x320. If I understand correctly, 240 horizonal rows of pixels (240p) and 320 columns.

If we rotate the image, that now requires 320 rows but is that too much for 15 kHz? I'm guessing that converting to 480i increases the resolution to 480 lines (which is enough for the 320) but requires interlacing?

Do I understand that correctly?

[Fudoh]

Yes, that's right. 24khz would be an alternative to stay progressive. Then you got a vertical resolution of 384 lines.

[matt]

Doesn't have to be a candy cab.

https://usermanual.wiki/Document/TaitoG ... 96656/html

I had one of these cabs back in college. It came with a full Metal Slug kit and the whole thing cost $75. Those were the days!

At the time I had a mix of vertical and horizontal PCBs, so I just left the bezel off and rotated it whenever I wanted to switch games. The process is easy and takes less than a minute - you just pick up the plywood piece and turn it. If you're making your own cab this is a great design to copy.

I think this design would be best with a 20" monitor, though. 27" might be too clumsy.

[orange808]

Doesn't have to be a candy cab.

https://usermanual.wiki/Document/TaitoG ... 96656/html

I had one of these cabs back in college. It came with a full Metal Slug kit and the whole thing cost $75. Those were the days!

At the time I had a mix of vertical and horizontal PCBs, so I just left the bezel off and rotated it whenever I wanted to switch games. The process is easy and takes less than a minute - you just pick up the plywood piece and turn it. If you're making your own cab this is a great design to copy.

I think this design would be best with a 20" monitor, though. 27" might be too clumsy.

Mine still had Double Dragon installed when I purchased it. I also appreciate the wheels on the back of the cabinet.