XPC-4 Shaking Screen in RGB

Started by 98pacecar, June 16, 2014, 08:41:04 AM

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So I'm really not having much luck wrapping my head around my XPC-4. I'm having an issue now where the entire screen shakes randomly when I run it in RGB mode. It does the same thing over DVI and VGA. It's not a pattern or anything, just a random, largely vertical shake. I've tried all of the output resolutions and while the lower resolutions seem to do it a bit less than the higher, they all have the shaking. I'm seeing this in games as well as in the POST and LHES screens.

When I switch to the D output mode, the shaking stops with the exception of what looks like a horizontal line or two right at the bottom of my monitor. But the bulk of the screen has a stable image. Again, this happens in all of the output resolutions. Another odd thing is that when I switch resolutions in D mode, I don't see any difference in the image or even what looks like a blank period while the XPC switches to the selected resolution. The video/s output mode acts and looks exactly the same as the D mode.

This actually seems to be getting worse, but I may be imagining that. I've tried the reset on the XPC with no luck. I've also bypassed the XPC entirely and run the output into the VGA in on my monitor and it was rock solid. I am using this with an LCD, a Sony if it matters. The image itself looks great in all modes, but the shake is keeping me from running it in VGA and using my scan line generator.

I feel like I'm just missing something on how to use the XPC, but so far my searches haven't turned up much in English. I did try to update the firmware as found on the SHMUPS forum, but that made no difference.

I guess my next step is to try and find a CRT that still works and drag it home to test. But before I go that far, is there anything I can adjust or try to knock this out?


Strange... I  dont have my XPC-4 here or I'd run some tests for you.   Do you have a hi def TV you can try?  You can use a DVI to HDMI adapter as output from the XPC.


I use mine on a LCD. I connect it through VGA and I have seen it randomly jitter or jump. I always tell it to auto-adjust (I think one of the buttons on the remote will do it with one press). After auto-adjusting it fixes the issue for me.

It doesn't do it for me every time, and sometimes if everything has been powered off I might try the exact same game again later without changing any settings on the XPC-4 and get the screen jumping again, but telling it to auto-adjust has always fixed the issue for me.


In your XPC-4 menu, go to the fourth option 画面調整 (Screen Settings) then go to the bottom option called スキュー (Skew). Adjust this a few notches in either direction until the shaking stops. That should be all unless you have other issues going on.


Thanks for the advice guys. I haven't taken the time to really test it out yet, but the skew setting that skpstmgs suggested appears to have solved the issue. Ill give it a more thorough test tomorrow, but for right now it's a ton better!

@skpstmgs, thanks for the help! Do you have any other tips or tricks for someone that knows little to nothing about the way these types of devices work? I'd love to know what all it is capable of doing, but there seems to be little knowledge shared in english. Even a simple faq or something might help me get a bit further down the road.  :)


Sure, I can try summing up everything I know about the XPC-4. Not sure how much that is, since I'm still learning about it myself, but let me gather up my thoughts and I'll have something for you within a day or so.


Thanks!!! I look forward to reading what you put together as you definitely know more about it than I do!


do you know if your monitor supports 60hz refresh rate? what model monitor are you using?


It appears to support 60hz. Sony SDM-HS95P/S. After using the skew setting in the XPC as suggested, it appears to be working ok. At least from initial testing.


Ok, I spent a couple of hours just messing around with my setup and after adjusting the skew setting yesterday, I noticed no shaking at all. I hate to risk jinxing myself, but I think this has taken care of this problem!

I very much appreciate all of the suggestions and am glad to have another issue behind me. On to the next one!! ;D


Disclaimer: I am no expert on the XPC-4, I'm just sharing my experience with it and what worked for me in my few months of using it with the X68000. Feel free to correct or add to what I have.
I have the most recent firmware installed on the XPC-4 which seemed to change the order of some of the menu options, so keep that in mind if you are using an older firmware.

XPC-4 "Processing" resolution: Under the first menu option 画面自動調整 (Automatic Screen Adjustment) , select the third option 半自動 (Semiautomatic).
This seems to adjust the internal processing resolution of the signal so it will do most of the processing at this resolution before upscaling it to your final resolution of your monitor, which will be whatever output you have selected.
In my case, I use a 1920x1080 Asus LCD, so most of my experience will be with the XPC-4 outputting to DVI@ 1080p.
I read that you are supposed to set this to some multiple of what your signal resolution is, but in my experience, setting it to 1920, which is the maximum, either gets me the same result or better than trying to set some multiple. Obviously if your monitor doesn't do this resolution, you will probably have to pick the maximum horizontal resolution your monitor supports.

After selecting the internal resolution manually, you will need to do the auto-adjust again by going to the first menu option 画面自動調整 (Automatic Screen Adjustment), then selecting the middle option 自動 (Automatic). After this, you can check the current status by selecting ステータス (Status) on your remote control under the green button on the top left. It should show the current (Internal processing horizontal resolution) x (input signal vertical? resolution). This barely makes any sense to me, so if anyone has more info on this, feel free to add.

Color "noise" in XPC-4: This seems to be a limitation of the device that will manifest itself as noisy patterns that are most evident in large areas of a single solid color. It seems that changing the brightness of the screen can change which tones/colors are affected the most, and there doesn't seem to be any perfect setting. Personally, I use a brightness setting of 49 which seems to minimize the noise in natural skin tones, as those look the most awkward with the weird color noise issue.
Increasing the internal processing resolution seems to make this noise "smaller" so it is less noticeable than usual. It might still be visible if you have your eye up to the monitor though.
The output resolution also affects how these appear, but I can't conclude what looks best here.

Changing brightness: Third option in the menu 画質調整 (Image Setting) -> first option 明るさ (Brightness)

Changing gamma: Third option in the menu 画質調整 (Image Setting) ->  second option ガンマ (Gamma)
I have mine set to 14. I think the default setting is a bit higher if I remember correctly. If you aren't familiar with what this setting does, load up Detana!! Twinbee and start the game. While the princess is talking with text onscreen, you might notice the background is greyish in color instead of black. Decreasing the gamma will make this grey appear closer to black, but it also cuts out details that are near-black, so don't set it too low.

Scrolling backgrounds don't appear smooth: Since the output framerate is locked on the XPC-4, it converts anything coming in to 60Hz, which means any input that isn't a multiple of this is going to appear choppy. Not sure what the exact output of the X68000 is, but I think it's around 55Hz, hence the framerate conversion and its inherent choppiness. I'm afraid there is not much you can do here.

Internal Processing Resolution -> Output Resolution: From my experience, I have not been able to get a perfect nearest neighbor upscale with this device. Using what I listed above, I can only get a "perfect" upscale on the y-axis, but not the x-axis. If you look at a game where sharp edges of sprites are easy to notice against a background (for example: Bubble Bobble), you can see what should be a single pixel from the X68K "averaged" or "blurred" across two different pixels on your screen horizontally. This problem doesn't seem to exist in the y-axis, at least from what I've noticed. Possible reasons why this doesn't work are: dot clock settings, skew, "internal processing" resolution not set correctly, some other unknown factor, or maybe the device is just imperfect. I don't currently have the answer to this.

XPC-4 won't autoscan correctly in some specific games/modes (takes forever to scan, then just ouputs a garbled screen): I experienced this issue in Marchenmaze when using a specific output mode when I had the manual internal resolution set to 1920. Using a resolution of 1366 is the highest that seemed to work without issues for that game.

XPC-4 autoscanning and "remembering" settings: the XPC-4 remembers the set "Internal processing" resolution for specific input parameters like resolution and probably some other characteristics (I assume signal range or something along those lines). What this means is that you might have to set this custom resolution a bunch of times as there are different resolutions and scan ranges that the X68K can output.

Along with each of these settings, it remembers the autoscanned screen edge settings, meaning some games might be slightly offscreen if it recalls the same setting from some other game that outputs the image at a slightly different offset.

While the autoscan is helpful in most cases, if a game uses any sort of black areas around the screen, the XPC-4 will crop these out and adjust the aspect ratio with the black parts omitted, meaning a game with pillarboxing will be stretched wide to reach the edges of the screen. For example, if you auto-adjust on the LHES screen, then load up Detana!! TwinBee, the XPC-4 will use the same settings for this game as it does on LHES, and should have black bars on the sides while playing. If you autoscan during the game, it will stretch the image making it appear fatter, and once you go back to LHES, since the two share the same graphics mode, the LHES will be cropped on either side. (Incidentally, Detana!! TwinBee also has a pseudo-"Vertical" mode which makes it appear in the aspect ratio of the arcade version which is thinner than the default X68K appearance)

It's worth noting that some options like overscan: fourth menu option 画面調整 (Screen Settings) -> second option オーバースキャン (Over Scan) and other screen size settings are saved across the board and won't reset on autoscanning, so don't play around with these unless you remember the default values, or are willing to do a factory reset through the menu.

Screen is shaking: Play around with the skew setting. Fourth option in the menu 画面調整 (Screen Settings) -> Last option in the menu スキュー (Skew). Turning it a few notches in either direction should get rid of the shake. You can also try doing autoscan again, but sometimes it still shakes after, and you might not want it to mess with the screen edges, so manually adjusting skew might be better.

Autoscanning games with mostly black borders like Metal Orange Ex: this particular game uses a mostly black background with quick-moving stars in it. These are always going to be troublesome as the XPC-4 has trouble detecting where the signal edge is with the fast moving and small stars. Best bet for this game in particular is to go to the screen where it previews the upcoming stages, and try autoscanning several times until you get everything inside of the screen, including the bobbing blue blob next to Chip-chan :).

XPC-4 can do a (line-doubling?) VGA passthrough: if you have the XPC-4 hooked up to a 31Khz CRT using VGA, and want to only use the XPC-4 for the 15Khz and 24Khz modes that your monitor doesn't support, just switch the output select to anything except RGB mode and it should do a fairly simple passthrough of the signal to VGA. From my very brief test of this, you won't get the input lag or the framerate-locking downsides of the XPC-4 while using the passthrough with the common 31Khz mode. Interestingly, you still get a status indicator overlay on the passthrough.

Okay, that is everything I can think of right now. Hopefully this helps someone else. Thanks for taking the time to read it.

I used the below document that I found (probably somewhere on these boards) for getting the Japanese menu names (as well as manually drawing Kanji on the IME pad in windows). Kudos to whoever made this. Note: I think this document is from an older firmware so don't count on the order being the same. It also misses a couple of sub-menu items.


Main menu

画面自動調整 Automatic Screen Adjustment
アスペクト Aspect ratio
画質調整 Image Setting
画面調整 Screen Settings
オプション Options
ズーム Zoom
TV出力モード TV output mode
D出力モード D output mode
RGB出力モード RGB output mode
スペシャル Special

Sub menus

画質調整 Image Setting
明るさ Brightness
色調整 Color Adjustment
ガンマ Gamma
黒調整 Black Adjustment
R調整 Red Adjustment
G調整 Green Adjustment
B調整 Blue Adjustment
シャープ Sharp
フリッカ Flicker

画面調整 Screen Settings
表示幅 Display Width
オーバースキャン Over Scan
水平位置 Horizontal Position
垂直位置 Verical Position
水平表示幅 Horizontal Display Width
垂直表示幅 Verical Display Width
入力水平位置 Input Horizontal Position
入力垂直位置 Input Vertical Position
入力水平表示幅 Input Horizontal Display Width
入力垂直表示幅 Input Vertical Display Width
ドットクロック Dot Clock
スキュー Skew

オプション Options
TV比率 TV Ratio
自動表示 Automatic Display
フリーズ Freeze
オートスキャン Auto Scan

ズーム Zoom
ズーム表示 Zoom Display
ズーム水平表示置 Zoom Horizontal Display Position
ズーム垂直表示置 Zoom Vertical Display Position
ズーム調整 Zoom Adjustment
ズームREC Zoom REC

スペシャル Special
AD調整 AD Adjustment
スルー水平同期REV Through horizontal synchronization REV
スルー垂直同期REV Through vertical synchronization REV


This is great information!! Maybe it should have a permanent home in the wiki??

Thanks again skpstmgs! I'd still be trying to deal with a shaky screen without your help!