Viewing Issue Advanced Details
ID Category [?] Severity [?] Reproducibility Date Submitted Last Update
07618 Color/Palette Major Always Apr 23, 2020, 00:15 Apr 25, 2020, 21:31
Tester ballyalley View Status Public Platform MAME (Official Binary)
Assigned To Resolution Open OS Windows Vista/7/8 (64-bit)
Status [?] Acknowledged Driver astrohome.cpp
Version 0.218 Fixed in Version Build 64-bit
Fixed in Git Commit Github Pull Request #
Summary MESS-specific 07618: astrocde and clones: Bally Arcade/Astrocade - Incorrect Color Palette
Description It has been noted for several years by users of the Astrocade emulation in MAME that the colors don't match up with real hardware properly. Some colors are close, while others are WAY off what they should look like under emulation. Some colors are completely wrong. I don't think that a proper bug report about this issue has been made until now.

Since I have been programming in the last few days using AstroBASIC under MAME, this has become even more apparent (and annoying) to me. A Bally BASIC programmer depends on the screen color because color changes made to the screen by one of the four shift keys must match the color of the key that is pressed on the 24-key keyboard overlay. In a couple cases, the shift keys are completely wrong (for instance, the red shift key turns the screen yellow).

Note that the color palette issue doesn't just affect Bally BASIC or "AstroBASIC," but it's easiest to spot the problem using the BASIC cartridge because you know what colors to expect on the screen when you press certain keys on the keyboard.

To make the I made a picture to allow people to see the color issues when using Bally Arcade/Astrocade emulation.

To make this error easiest to imagine, I made a picture which I call "Color Comparison in AstroBASIC: Real Hardware vs. MAME." I've attached it to this report. The picture is a side-by-side AstroBASIC screen comparison to make it easy for anyone to see the differences between the colors on real hardware and MAME. I've made one picture that includes what the colors of the shift-word keys look like on a real astrocade next to colors as they are seen in MAME. To make this easier to understand, each screenshot that I took explains what you're looking at on the screen.

I took screenshots of my CRT TV using my camera. The colors are about accurate to how they look on my actual CRT. The red is little off in the picture of my CRT (the CRT's screen is more red, not murky reddish-pink in the picture), but the camera's pictures are approximately right. As you can see, the colors under MAME are sometimes close and sometimes not even in the same color range.

Here is a breakdown of the color differences you'll see in the compilation of pictures, as seen from top to bottom:

1) AstroBASIC - Default Colors - B&W - MAME gets this about right.
2) AstroBASIC - Green Shift Key - MAME's shade of green is off, but at least it get the correct color. It still should be adjusted in MAME.
3) AstroBASIC - Red Shift Key - MAME is completely wrong. The screen should be red, but it is yellow-ish/gold instead.
4) AstroBASIC - Blue Shift Key - MAME is wrong here. The sceen should be blue, but it is light-purple instead.
5) AstroBASIC - Words/Gold Shift Key - MAME's shade of "gold" is off (it's bright yellow), but at least it's in the same-ish color range.

I hope that this helps a programmer track down the issue that the Astrocade emulation in MAME has with displaying the correct colors.

I posted about this issue on the Bally Alley Astrocade dicussion group on Groups.io and Lance Squire, a member there suggested:

"I'm guessing it's probably related to the colour differences between the arcade and home systems. I'm presuming M.A.M.E. is set for the arcade. [...] I ran into colour issues when making the Christmas demo on M.E.S.S. [...] I made a colour comparison chart comparing M.E.S.S.'s pallette to what I could vidcap from my Bally/Astrocade. It might be helpful if mess and mame are using the same pallette for the astrocade. If not, should be easy to update."

I then asked, "Wait a second... the arcade games that use the 'astrocade chipset' have a different color palette than the Astrocade home system? On real hardware? How is this possible? Or, is the color palette just incorrect in MAME for the arcade games that use the 'strocade chipset' too?"

Lance answered, "I don't know for sure, but the arcade systems are pretty much direct to
monitor while the home arcade goes through the RF box. I'm sure there is probably some differences from that."

Kevin Bunch mentioned, "I have noticed some palette changes between my monitor and my video capture setup too - nothing that dramatic, but I do think that the way the system processes color probably lends itself to these kinds of issues. Tom Meeks mentioned to me that he moved away from the UV1 (and the Bally color palette) because it's so oversaturated - I wonder if that may be a factor."

Finally, Ken Lill says, "It COULD be that the RGB was using a different combination of capacitors/ resistors to get their colors than the R-y B-y combination that used an R/C configuration to generate G-y. That can be tricky to get just right. The older modulators used with the Bally had different colors (sorry for the American spelling, Lance) that the latest, more brilliant, ones."

I hope that this is enough information to get someone to work on this fix Astrocade's color palette. The games work okay with the color palette wrong, but it's very difficult to use BASIC, as the color of the BASIC screen clues-in the programmer to which letter/number or symbol will show up on the Astrocade's screen when the user presses a key on their keypad.

If anyone needs me to make any tests using real hardware, then I can do that for them.

Adam
Steps To Reproduce The easiest way to reproduce this error with the color palette is to use any version of MAME and run "AstroBASIC." Then press the keys that are setup under emulation to produced the four shifted color keys. You should get Green, Red, Blue and Gold, but instead you'll get the colors I show in the uploaded picture attached to this bug report.

Viewing the 24-key keypad's overlay should help give you an idea of which keys to press:

https://ballyalley.com/pics/keypad_overlays/full_size/AstroBASIC%20Overlay%20(150%20dpi).jpg

Also, coming to terms with AstroBASIC just enough to even test the color palette might not be easy. These two tutorial videos that I made may help you get started with getting "AstroBASIC" setup so that you can test for this color palette error:

1) Setting up Astrocade Emulation Using MAME



2) Overview, Review and How to Use Bally BASIC / "AstroBASIC" for Bally Arcade/Astrocade

Additional Information The issue with the color palette seems to affect all version of the home versions of the Astrocade. It may also affect the arcade games Gorf, Wizard of Wor (the "Astrocade chipset" games), but I'm not sure as I don't have much experience with those games on real hardware.
Github Commit
Flags
Regression Version
Affected Sets / Systems astrocde and clones
Attached Files
jpg file icon Astrocade_Color_Comparison_Real_Hardware_Vs_MAME.jpg (2,100,260 bytes) Apr 23, 2020, 00:15 Uploaded by ballyalley
Astrocade Color Comparison - Real Hardware vs. MAME
Relationships
related to 02682Confirmed  gorf and clones: Colors washed out in Astro Battle 
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