Simulated Composite Video for PCXT Core

[spark2k06]

Still in the testing phase...



Thank you @Mills for initiating this development and calculating the first RGB table from the corresponding patterns.

[spark2k06]

Burger Time

Burger Time.png (614.52 KiB) Viewed 3575 times

[spark2k06]

I attach it so that you can try it out, there are several composite video games, You will also need the attached Main MiSTer, because this version also has the implementation of the new real FDD, and sorgelig has not yet released the release it needs:

http://nerdlypleasures.blogspot.com/201 ... phics.html

It is possible that when switching to composite video the colours do not come out well, deactivate and activate it until it comes out well... it is something that I have to correct, it has to do with the synchronisation of the OSD event.

Share screenshots!

[akeley]

VileR, of the ASCII art fame, is also quite an expert on all things CGA. Worth having a look perhaps: https://int10h.org/blog/2022/06/ibm-515 ... a-palette/

[spark2k06]

Issue with switching from normal mode to composite video solved. I attach the new binary and also provide the specific and experimental prerelease branch I have created:

https://github.com/MiSTer-devel/PCXT_Mi ... -composite

[spark2k06]

Some screenshots:

composite.png (646.26 KiB) Viewed 3225 times

[LamerDeluxe]

Great work! As an Amiga user at the time, I have no nostalgia for old PCs, but I have really been enjoying following the development of this core.

[thorr]

This is so completely awesome. Great job! I still haven't tried PCXT because I am way too busy working on constructing my arcade cabinet, but I am extremely excited about the core.

ao486 requires use of the scaler which adds a bit of lag. Does PCXT work with CRT VGA monitors when displaying CGA graphics with no lag, and does this composite simulation mode add any lag? Can CGA mode work on CRT TV's without the scaler and would this color mode work on that? Thanks!

[spark2k06]

The colours are fixed when there are 16 colours on the screen:

Composite_16_colors.png (631.26 KiB) Viewed 2981 times

On the other hand, as it is currently not possible to display the high-resolution screen properly or more than 16 colours, the composite mode (selectable from the OSD) is only applied in modes that support this display.

Now available in the pre-release branch:

https://github.com/MiSTer-devel/PCXT_Mi ... prerelease

I'm also attaching it here for you to try it out until I publish the next release.

[breiztiger]

Thanks for your hard work on this core !!!

[somhi]

That simulated output is great.
Going real, the Graphics Gremlin has a composite module which output could be activated. I'm testing it with the non-MiSTer ports and ATM I'm getting B&W image. I'm using an LCD so that might be the culprit. I suggest porting those changes to MiSTer so other people could test it also.
I'm getting composite output directly from a FPGA pin and just I'm adding a serial resistor of 170 Ohm aprox, so no higher voltage of 1V could reach the TV input.
Check one of the latest commits from the DeMiSTify devel branch.

[thorr]

Would this work for real composite output? It looks like PCXT is already supported: viewtopic.php?p=61543#p61543

[spark2k06]

That simulated output is great.
Going real, the Graphics Gremlin has a composite module which output could be activated. I'm testing it with the non-MiSTer ports and ATM I'm getting B&W image. I'm using an LCD so that might be the culprit. I suggest porting those changes to MiSTer so other people could test it also.
I'm getting composite output directly from a FPGA pin and just I'm adding a serial resistor of 170 Ohm aprox, so no higher voltage of 1V could reach the TV input.
Check one of the latest commits from the DeMiSTify devel branch.

In both the prerelease and main branches, I already left the original Graphics Gremlin file to handle the composite video output:

https://github.com/MiSTer-devel/PCXT_Mi ... omposite.v

Any developer who wants to test this module by taking the output to a MiSTer pin, just add the call in the cga.v module:

Code: Select all

    
    // Composite video generation
    cga_composite comp (
        .clk(clk),
        .lclk(lclk),
        .hclk(hclk),
        .video(video),
        .hsync(hsync_int),
        .vsync_l(vsync_l),
        .bw_mode(bw_mode),
        .comp_video(comp_video)
    );

However, even in the original Graphics Gremlin project, it is said that colour generation can be problematic due to timing issues... but I leave it here for anyone who wants to experiment with it.

[suww37]

It's amazing. Your results show a satisfactory screen on a crt screen rather than an LCD monitor. However, the wrong timing on a 15khz rgb (ex. sony pvm) monitor is still not improving. I'm eagerly waiting for this. Is there anyone who can solve this?

[Newsdee]

This is really amazing - I'm rediscovering the early PC game library when seen through this color mode!

Some games have a strong Apple II vibe (Adventure in Serenia), some are much better looking (Burger Time, Bruce Lee), others seem to not be designed for Composite but still show nice results (Buggy Rider).

Is there a list somewhere of compatible games?

[spark2k06]

This is really amazing - I'm rediscovering the early PC game library when seen through this color mode!

Some games have a strong Apple II vibe (Adventure in Serenia), some are much better looking (Burger Time, Bruce Lee), others seem to not be designed for Composite but still show nice results (Buggy Rider).

Is there a list somewhere of compatible games?

Here is the list

https://www.mobygames.com/attribute/she ... Id,29/p,4/
http://nerdlypleasures.blogspot.com/201 ... phics.html

[spark2k06]

New simulated composite video and up to 1K colours..., no huge tables, all formulas. Thanks again @Mills for your collaboration:

new_composite_video.png (882.25 KiB) Viewed 2254 times

Soon in the official release, in the meantime, I attach binary for testing.

[spark2k06]

Commit now available in the prerelease branch:

In case anyone wants to take a look at it, or find any point of improvement before releasing it for all users.

https://github.com/MiSTer-devel/PCXT_Mi ... 49cdb7e27d