Apricot Xi Profile

[roddersuk]

I've just got an Apricot Xi and after putting new Rifas in the PSU it works, hard disk and all! Now I want to get a display so I was hoping to use an RGBtoHDMI to do the business but the video on the Xi is a bit unusual. 800x400 resolution, 15Mhz pixel clock, 71.9Hz vertical frequency, 16kHz horizontal.
I've played around with the Hercules profile but can't get a stable image.
Is what I'm trying to do possible and if so can anyone give me some tips on how to configure it.
Thanks.

[roddersuk]

Here's a capture of the screen. I've turned on the V-sync indicator which scrolls and you can see that the display is duplicated. Nothing I have tried secures the sync or stretches the display to fit the screen.

[roddersuk]

Well, a bit of progress. With line doubling and height set to 100 I get this:

But genlock is still inhibited and it seems to be missing some scan lines.

[roddersuk]

Getting closer, the image looks good except it flashes!

here's the profile:

PC_Xi_Gfx.txt

and this is what it looks like

VID_20260304_160208380.mp4

[c0pperdragon]

When the screen flashes even if it is otherwise looking correct, this may be due to the pixel rate (can be set in the geometry menu) not matching the actual pixel rate. In this case the RGBtoHDMI detects that something is outside spec and this somehow causes the flashing.

[roddersuk]

I've been tweaking the pixel clock and line length, the error is in single figures ppm. I'll try fiddling with it a bit more.
I believe the display is interlaced as with the height set to 400 I get two frames on screen whereas the display above is with height of 200. However, changing the Video Type from Progressive to Interlaced doesn't seem to do anything. My main concern is that the RGBtoHDMI can't handle the 72/36Hz frame rate or that it doesn't understand the encoding of the video sync signal to identify the od/even frames.