MiSTer 720p or 1080p through eeColor back to 240p for CRTs

[HDgaming42]

This is a sort of evolution from this earlier post:
viewtopic.php?p=1413713

I want to use an external LUT box with my CRTs for retrogaming. Forget all the connection format conversions required for a moment. Is it possible to use a MiSTer FPGA to generate a line multiplied 240p signal within a standard 720p/1080p format, and then use something (Retrotink 5x-pro maybe) afterward to cleanly decimate it back to 240p? Is that math even possible? I recognize I'm going from 4x3 to 16x9, but I'm thinking there has to be something that can crop as well as decimate.

I really want to make this work, but if it doesn't, I don't really have a use for my LUT box any more as it doesn't to 4K.

Thanks!

[Syntax]

Mister has dual analog/digital outputs.

Youd run the digital video at mode 8 (1920x1080) in the MiSTer ini and just let the analog signal run without line doubling it to get your 240p.

[HDgaming42]

Mister has dual analog/digital outputs.

Youd run the digital video at mode 8 (1920x1080) in the MiSTer ini and just let the analog signal run without line doubling it to get your 240p.

I opted for just the bare board so convert HDMI to analog.

~~

I've got the fever for this again and this I've come up with a chain that should theoretically work and only involves 3 devices. Sanity check anyone?

Generating an integer scale to be processed:
MiSTer custom modeline of 1920x1200 @ 60Hz
video_mode=1920,48,32,80,1200,3,6,26,154128
reported as successful for multiple users here:
https://misterfpga.org/viewtopic.php?t=3366

Applying a corrective LUT:
eeColor can accept and process 1920x1200 @ 60Hz
https://www.liftgammagain.com/forum/ind ... 468/page-2

Scaling to 240p:
Extron DSC 301 can accept 1920x1200 with reduced blanking (only 60Hz, not 59.94) and can output 1920x240 @ 60Hz
https://www.extron.com/product/dsc301hd

Conversion to analog:
my HDMI to HD15 converter can process 1920x240p for display on CRTs, but will 60Hz work?

Before I try to wrap my head around both MiSTer custom modelines and loading custom EDIDs into my 301, does anyone see any roadblocks to this approach? Will the extron discard lines or combine them do you think?

[Fudoh]

Very much looking forward to the results!

I don't see you have to push the limits on machines involved. Wouldn't a 720p or 960p output work just as fine?

When Marco tried the IN1606 for 240p output he could only get a 55Hz'ish output with lots of dropped frames*, so you will likely run into the same problems using the 301. Maybe a GBS-C instead for the final downscaling step?


* https://www.youtube.com/watch?v=g4MZ3y9Q5kI

[Josh128]

This is a sort of evolution from this earlier post:
viewtopic.php?p=1413713

I want to use an external LUT box with my CRTs for retrogaming. Forget all the connection format conversions required for a moment. Is it possible to use a MiSTer FPGA to generate a line multiplied 240p signal within a standard 720p/1080p format, and then use something (Retrotink 5x-pro maybe) afterward to cleanly decimate it back to 240p? Is that math even possible? I recognize I'm going from 4x3 to 16x9, but I'm thinking there has to be something that can crop as well as decimate.

I really want to make this work, but if it doesn't, I don't really have a use for my LUT box any more as it doesn't to 4K.

Thanks!

Why go through all that? Just make the Mister output directly to 240p. Its perfectly capable of it, Ive done it.

[HDgaming42]

Very much looking forward to the results!

I don't see you have to push the limits on machines involved. Wouldn't a 720p or 960p output work just as fine?

When Marco tried the IN1606 for 240p output he could only get a 55Hz'ish output with lots of dropped frames*, so you will likely run into the same problems using the 301. Maybe a GBS-C instead for the final downscaling step?


* https://www.youtube.com/watch?v=g4MZ3y9Q5kI

Hmmm. For some reason I had it in my head that 720p wasn't a great choice for later downscaling as it's 3x, but 1200 is 5x so I'm not sure where I got that impression. You're right, life might be easier at 720p.

I've been away from this hobby for quite a while, only briefly checking in from time to time and that video you linked was great. Initially disappointing to learn about the dropped frames. I have a pair of GBS-Cs but they've always performed a bit flaky with my gear so I was hesitant to revisit them.

Turns out the EDID that Marco used wasn't ideal, and a better one (also different hardware) performed much better!
https://www.youtube.com/watch?v=Wg3p7y-esPI

As the EDID was provided in the comments I'll give this a shot with my 301 HD this evening (hopefully) and report back!

[HDgaming42]

This is a sort of evolution from this earlier post:
viewtopic.php?p=1413713

I want to use an external LUT box with my CRTs for retrogaming. Forget all the connection format conversions required for a moment. Is it possible to use a MiSTer FPGA to generate a line multiplied 240p signal within a standard 720p/1080p format, and then use something (Retrotink 5x-pro maybe) afterward to cleanly decimate it back to 240p? Is that math even possible? I recognize I'm going from 4x3 to 16x9, but I'm thinking there has to be something that can crop as well as decimate.

I really want to make this work, but if it doesn't, I don't really have a use for my LUT box any more as it doesn't to 4K.

Thanks!

Why go through all that? Just make the Mister output directly to 240p. Its perfectly capable of it, Ive done it.

Step 2: To apply a corrective LUT to calibrate my CRT using my old eeColor that no longer has a purpose now that I've upgraded to something that can process UHD.

[Guspaz]

The mister already has support for LUTs on the video output, an external device is redundant.

[HDgaming42]

The mister already has support for LUTs on the video output, an external device is redundant.

The MiSTer being able to hold a 65pt cubed 3D LUT is news to me. Do you have a link to the documentation?

[HDgaming42]

Haven't yet tried to integrate the eeColor but this still ended in failure. Loaded the EDID. Applied it to the output. MiSTer was outputting bog standard 1280x720p.
Extron was outputting via the provided 1920x240p EDID. Image appears distorted through the Portta converter.

I then added an extron RGB 203 into the chain but the picture remained the same. The distortion is the same across an RGB modded Sony and a PVM-2530.

I also tried a GBS-C to do the downscaling (MiSTer to Portta to GBS-C to TV) and it looked the same. I've never had my GBS-C properly perform downscaling though, and passthrough of 240p results in the image being overblown and rolling.

Any ideas?

[orange808]

Digital input at high resolutions, correct?

An HDMI Corio2 machine can downscale 720p to 240p and it's clean. You'll have to dial it in manually. With an adapter, you can get analog output from the machine.

I still haven't purchased an OSSC Pro, but I understand it has robust downscaling capabilities with the analog output. If I was serious about downscaling an HDMI source, I'd investigate the OSSC Pro first. The OSSC Pro firmware should mature into the best downscaler in existence, if that hasn't happened already.

Seems like a lot of extra effort and frustration. Why not pull analog video from the MiSTer and use an inexpensive distribution amp (aka "splitter")? That way, you could feed multiple video processors the native analog video signal. Use your upscaler for your modern display and feed the analog video to your CRT chain.

If this is a dual RAM thing, investigate GroovyMiSTer and a PC for some of your needs. If this is related to your analog board, there are cores with pulse width modulation. You don't really need dual RAM to play a few odd games; run them on a PC with GroovyMiSTer, instead. You don't really need a new board, PWM delivers indistinguishable results on PS and N64--and GroovyMiSTer supports it (as well). You don't have to output HDMI.

[HDgaming42]

Digital input at high resolutions, correct?

An HDMI Corio2 machine can downscale 720p to 240p and it's clean. You'll have to dial it in manually. With an adapter, you can get analog output from the machine.

I still haven't purchased an OSSC Pro, but I understand it has robust downscaling capabilities with the analog output. If I was serious about downscaling an HDMI source, I'd investigate the OSSC Pro first. The OSSC Pro firmware should mature into the best downscaler in existence, if that hasn't happened already.

Seems like a lot of extra effort and frustration. Why not pull analog video from the MiSTer and use an inexpensive distribution amp (aka "splitter")? That way, you could feed multiple video processors the native analog video signal. Use your upscaler for your modern display and feed the analog video to your CRT chain.

If this is a dual RAM thing, investigate GroovyMiSTer and a PC for some of your needs. If this is related to your analog board, there are cores with pulse width modulation. You don't really need dual RAM to play a few odd games; run them on a PC with GroovyMiSTer, instead. You don't really need a new board, PWM delivers indistinguishable results on PS and N64--and GroovyMiSTer supports it (as well). You don't have to output HDMI.

These are all great suggestions - thank you. I can run my MiSTer to my CRTs without issue, the complication is integrating colour correction via the eeColor box, which only takes in HDMI and only processes (for the most part) 720p and 1080p. I can run the MiSTER into it at 720p and feed an HDMI monitor no issues there. It is getting the signal back down to 240p that has been a challenge.

I had an DVDO VP30 that theoretically should have been able to do it, but I could never dial it in properly. Later I think it was learned the dot clock (?) probably wasn't well suited to the task.

I had a line on a cheap Corio2 ages ago but that fell through.

Now it seems that the Extron 301 HD should be able to do exactly this with a custom EDID. It works on a DVS 605 and another unit as well. I feel like I'm close, but I'm missing something as far as configuration goes.

Once this is all settled I will integrate everything into my SMX matrix switch so that I can colour correct all my SD/HD signals through the eeColor (65pt cube) to multiple monitors (6 presets available) while my UHD signals will be calibrated to my main display via a 33pt cube held in a decklink device.

I've solved retro signals getting colour corrected (nice to toggle between D65 and D93 at the touch of a button), but just need a path back to 15kHz CRTs.