Monochrome video out vs Composite color burst options

[mark_k]

I started to look at patching Cannon Fodder to set the bplcon0 COLOR bit (following from this thread. WinUAE doesn't show any change in visible output when the COLOR bit state is changed. [Logging when bplcon0 is written with COLOR=0 would be a good addition to the new custom-logging features...]

But I noticed two options which seem to have the effect of making the entire image greyscale: "monochrome video out" (Display) and "Composite color burst" (Adv. Chipset). What's the difference between them?

In playing with those I noticed a couple of issues. First Monochrome video out:
- With A500-like config, line mode "Double, fields", start emulation and boot some demo.
- Press F12, enable Monochrome video out and click OK. The display is shown in greyscale, but also the line mode seems to have changed to Scanlines. It still shows Double, fields in Display settings.
- Repeat but starting with line mode Double. Line mode (correctly) remains the same when you enable Monochrome video out.

Now Composite color burst:
- Using an A500-like config with line mode Double, start emulation and boot some demo.
- Press F12, in Adv. Chipset un-check Compatible Settings. Enable Composite color burst. Click OK. Display is still in colour.
- Press F12, change line mode to Scanlines, click OK. Now display is in greyscale.
- Press F12, change line mode back to Double, click OK. Display is still in greyscale.

(Also, the sense of the Composite color burst checkbox seems to be reversed? Colour burst present means display should be in colour.)

[Toni Wilen]

Originally Posted by mark_k

I started to look at patching Cannon Fodder to set the bplcon0 COLOR bit (following from this thread. WinUAE doesn't show any change in visible output when the COLOR bit state is changed.

Yes because default is RGB output. (I have never used anything else than RGB out)

[Logging when bplcon0 is written with COLOR=0 would be a good addition to the new custom-logging features...]

I don't count this as invalid. It needs some extra option. It is also easy to confirm with burst option.

But I noticed two options which seem to have the effect of making the entire image greyscale: "monochrome video out" (Display) and "Composite color burst" (Adv. Chipset). What's the difference between them?

Greyscale = forced greyscale output. (like using A500 video out. Excluding image quality issues)
Composite color burst = emulate color burst bit. (It is not enable/disable color burst option).

Greyscale internally is video port adapter (like genlock or ham-e) which have limited doubling mode support. It will be fixed someday..

[Toni Wilen]

Originally Posted by Toni Wilen

Greyscale internally is video port adapter (like genlock or ham-e) which have limited doubling mode support. It will be fixed someday..

Fixed (genlock and grayscale). Grayscale "monitor" is now last monitor step: if grayscale is enabled, CD32FMV and Genlock output is also in grayscale. (Not that you can connect genlock to b&w or composite out connector but full grayscale makes more sense)

[mark_k]

Testing the Composite color burst option with 4.2.0b3, output seems to always be monochrome when that box is checked? E.g. the Kickstart insert WB disk screen. Config I tested with at
hxxps://www.media!fire.com/file/c1ci5xxt9n0zh4n/A500_1.2_CannonFodder_test.uae.zip/file

[Toni Wilen]

COLOR bit was masked out before checking if BPLCON0 value changed. Which made it only work if COLOR bit was never set. Fixed.

[mark_k]

Thanks, that feature seems to work OK now.
Tiny hack test program:
hxxps://www.media!fire.com/file/48d94ix85aadba9/bplcon0_COLOR_test.tar.gz/file

Load color0test (executable) into DF0: and start emulation with Kickstart 1.x. With composite color burst checked should see blue/grey stripes on WB screen (and some display corruption). Press left mouse button to exit.

[Toni Wilen]

It isn't cycle-accurate

Assuming COLOR bit is not latched by Denise, it should only affect colorburst if it is enabled when colorburst is being generated.

Also what happens if color burst is enabled for some lines but not all? (I only care about old "analog" CRT TVs. Non-CRTs or later models with digital processing are not included) Some lines have color, some don't or something else? (For example what happens in PAL mode if only every other line has color burst?)

(Yes, pointless because in real world only A1000 has COLOR bit and probably no one did any color bit tricks. But interesting!)