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ramapcsx2 / gbs-control

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Can the GBS output composite sync? #152

Open pgrAm opened 3 years ago

pgrAm commented 3 years ago

Hi, I'm using GBS-Control to downscale 480p to 240p for my RGB monitor, however my monitor is composite sync only. Is it possible to get the gbs to output a composite sync? I know I can use a sync combiner, but it would be obviously better if the gbs can do this without extra hardware.

ramapcsx2 commented 3 years ago

The chip can't output a pure CSync signal, sorry. There is functionality to embed CSync in the Luma signal, to get Component Video output. That is the only way I know of, and of course it requires you to use Component.

If you plan on doing a sync combiner, please share your results! :)

pgrAm commented 3 years ago

Yeah I did build a sync combiner, 2 actually. I tested with two monitors/TVs (Sony KV1311cr & KV25XBR, according to the manual the kv25XBR has a vsync input but I couldn't get it to work)

The first sync combiner used a "passive" AND gate from here, and the second used a 74ls86 from here. The "passive" AND version worked great on both monitors between the output of the gbs and the input of the monitor, and so did the XNOR. I also used a sync combiner on the input of the gbs because I got poor results down scaling from RGBHV sources. I could not get the GBS to sync using the AND version but it did work the XNOR, I expected this because AFAIK the gbs uses a PLL.

I'm pretty happy with the results, the sync combiner is a small box in line with the vga cable so its not too bad in terms of extra complexity. Now I only wish I could get the GBS to scale from 480p to 480i as well

gingerbeardman commented 3 years ago

@pgrAm how does downscale RGBHV improve with the sync combiner?

pgrAm commented 3 years ago

@gingerbeardman, as detailed in issue#128, downscaling to 240p from RGBHV sources can have serious artifacts. I don't 100% understand why this is, but it is fixed by using a sync combiner at the input to the gbs.

Nuck-TH commented 3 years ago

@gingerbeardman scaler chip has limitations when it works with RGBHV video which are circumvented when syncs are combined and video processed as RGBS.

gingerbeardman commented 3 years ago

@pgrAm can you post a photo of your setup? I would like to replicate it. Thanks!

pgrAm commented 3 years ago

@gingerbeardman sure, its pretty simple I think

IMG_20201014_172519

The 480p RGBHV (VGA) signal goes in through the blue cable, into the XNOR sync converter (powered by 5v on vga pin9). Then into the gbs

IMG_20201014_172756

The black cable goes into the second "passive" sync converter (the clear plastic box), and into a passive adapter which allows me to plug dsub into the sony RGB multi input.

gingerbeardman commented 3 years ago

Great, thanks, I'll need the XNOR. Or can I buy one of those online?

Arnold101knight commented 3 years ago

what is the schematics or a guide to build the black combiner? passive

gingerbeardman commented 3 years ago

@Arnold101knight scroll up for links to schematics

eimparas commented 3 years ago

@gingerbeardman sure, its pretty simple I think

IMG_20201014_172519

The 480p RGBHV (VGA) signal goes in through the blue cable, into the XNOR sync converter (powered by 5v on vga pin9). Then into the gbs

IMG_20201014_172756

The black cable goes into the second "passive" sync converter (the clear plastic box), and into a passive adapter which allows me to plug dsub into the sony RGB multi input.

mey i have the schematics of the 2 boards ? (one in the clear box and the other on the scart

gingerbeardman commented 3 years ago

@finos2 the clear one is linked above: https://github.com/ramapcsx2/gbs-control/issues/152#issuecomment-708020588

gingerbeardman commented 3 years ago

You need to ask @pgrAm

twotone8 commented 3 years ago

Thanks Gingerbearman. @pgrAm, i'm attempting to build my own passive adapter and was curious where you purchased your HD15 to HD15 connector hood. It looks quite tidy.

pgrAm commented 3 years ago

@twotone8, The clear one I 3d printed and the black one I can't recall, it was sitting in my parts bin for a while, but you can get similar ones on mouser, digikey etc.

bob15357 commented 3 years ago

Thank you @pgrAm This was the setup I needed. I used the circuit from passive sync combiner found on the RetroRGB site here and used it before the GBS Control board on the input. On the back output, I have a 15khz passive combiner in got from here This works for downscaling VGA 31khz sources like dreamcast and xbox360 over vga out to my Seleco SMV-290 that takes 15khz Scart 240p input.

santiis2010 commented 2 years ago

Thank you @pgrAm This was the setup I needed. I used the circuit from passive sync combiner found on the RetroRGB site here and used it before the GBS Control board on the input. On the back output, I have a 15khz passive combiner in got from here This works for downscaling VGA 31khz sources like dreamcast and xbox360 over vga out to my Seleco SMV-290 that takes 15khz Scart 240p input.

I did the same Passive Sync Combiner from Bob web site but is not working for me :|