MiSTer FPGA Forum

Hello.

I'm using a 17" CRT VGA with my Mister (connected via IO board or HDMI direct video).
Scandoubler is by far the best image quality with most cores.
No worries about aspect ratio, scaler options, very crisp image and good scanlines.
Unfortunately I have a major problem with all interlaced resolutions : The scandoubler get disabled.
With Minimig PAL and NTSC laced output 15.6 Khz.
SNES PAL laced is 15.6 Khz and NTSC laced 15.74 Khz.
For the SNES core I falled back to scaler with good results.
For Minimig I can't get pixel perfect results using the scaler.
Is it fixable ?

Thanks !

darky_mtp wrote: ↑Tue Aug 03, 2021 10:16 am Hello.

I'm using a 17" CRT VGA with my Mister (connected via IO board or HDMI direct video).
Scandoubler is by far the best image quality with most cores.
No worries about aspect ratio, scaler options, very crisp image and good scanlines.
Unfortunately I have a major problem with all interlaced resolutions : The scandoubler get disabled.
With Minimig PAL and NTSC laced output 15.6 Khz.
SNES PAL laced is 15.6 Khz and NTSC laced 15.74 Khz.
For the SNES core I falled back to scaler with good results.
For Minimig I can't get pixel perfect results using the scaler.
Is it fixable ?

Thanks !

Hi, I might be incredibly wrong here but I don't think the scaler works with interlaced content, I'm sure Sorg said he has no plans to implement it either. Getting interlaced content to work either needs to be through the vga_scaler=1 or on a CRT that supports 15khz output... Problem with the Amiga is it just outputs all kinds of weird and wonderful resolutions so getting it perfect is difficult.

Originally I went with a nos VGA CRT and it has its issues with interlaced content, so I've now gone with a consumer grade TV as the vast majority of what I use is Amiga and console games, however it now means that ao486 and the Mac cores don't work well/at all. There is no one perfect option for CRT just like there wouldn't have been back in the day, a multisync monitor is probably as close to perfect as possible if one can be found.

Using VGA on real Amiga is possible with two different devices : Scandoubler and Scandoubler with Flicker Fixer.
Flicker fixer have a frame buffer so it haves to store both half frames to output full image.
Scandoubler only doubles lines.
I don't have a scandoubler but I think it can works with interlaced screens, storing odd line, output it at 31 Khz followed by an empty line. At the end of the half frame, doing the opposite : display an empty line followd by even line.
Interlaced don't get deinterlaced (and you don't get deinterlacing artefacts).

For scaling minimig you should use at least 540p for interlaced content, that is sort of the minimal viewport settings for cutting PAL, since the core is set up for 1080p scaling, especially with megaAGS.

darky_mtp wrote: ↑Tue Aug 03, 2021 10:58 am Using VGA on real Amiga is possible with two different devices : Scandoubler and Scandoubler with Flicker Fixer.
Flicker fixer have a frame buffer so it haves to store both half frames to output full image.
Scandoubler only doubles lines.
I don't have a scandoubler but I think it can works with interlaced screens, storing odd line, output it at 31 Khz followed by an empty line. At the end of the half frame, doing the opposite : display an empty line followd by even line.
Interlaced don't get deinterlaced (and you don't get deinterlacing artefacts).

You might be right on the interlaced output, like I said I wasn't sure. I just have a memory that was something about the scandoubler and interlaced output, it affected the Sonic 2 two player levels on the Megadrive which wouldn't work as they work in interlaced mode. Hopefully someone might know a bit better, maybe the other posters recommendation might work too.

Edit. I actually have an Indivision ECS v2 on my A500 and to any display the output is amazing, on MiSTer with the Minimig core things never seem quite so good

Darky_mtp is talking about dedicated "scandoubler" device for using 15khz from real Amigas on VGA monitors. But it might be a bit of a misnomer to call a de-interlacer of any kind a mere scandoubler. At any rate mister's scandoubler is not going to de-interlace at all, mister's built-in framebuffer is instead tied to the scaler which has de-interlacing capabilities.

Even at that, the scaler seems to assume that it working on actual interlaced content (i.e. alternating every other line.) Sonic 2's mode where instead it draws continuous halves of the screen is de-interlaced incorrectly by mister scaler, with obvious combing artifacts, though at least you will get something visible and mostly playable on your display.