PAL Gamecube RGB to VGA mod?

I've come across this mod, which seems to use the Gamecube AV out (PAL, as it has RGB on the analogue port). However, wouldn't I still need an upscaler, as all the LM1881N does is split the composite signal to H-Sync and V-Sync, still leaving me with 15Khz (or CGA)?

 

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I don't know. While that would seem to hold up in theory, I can't help but think that somebody would've made a bunch of cables/boxes doing so by now?

 

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In Amiga land, scan doublers are common to connect RGB to VGA.

Whether its that simple tho, I do not know.

 

Doubling the sync signal alone isn't enough, because the RGB lines will be the same "size as before" meaning that it would produce only a derp image on the screen like this: odd lines would be the original lines first half, and even lines would be the second half.

To fix that there needs to be a circuit that takes the original lines and store them in a memory and reading them at double speed (to match with the doubled sync rate). It's easy, but has it's own design challenges.

 

I am trying to make a converter too, with the SCART-cable, and found some images that worked for people on DVD-players (same schematics as OP). It looks promising, altough something is bothering me. Normally the input signals for VGA are progressive, like 480p. A PAL Gamecube is only sending 480i(/576i?), so will a VGA monitor/beamer accept interlaced signals? Can't find much on the internet about this..

Edit: Generally, VGA monitors doesn't accept a signal from an interlaced source. However, with GCOS, 480p can be forced, sometimes with just PAL games (not NTSC). I wonder if there will be a forced 480p over the SCART cable with this method (and not only over component)??

Images:
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scart output:

 

Whether the Gamecube outputs 480i or 480p is dependent on software and as only NTSC games support 480p, it would require either a PAL Gamecube with a modchip or an NTSC console with an internal VGA modification (obviously not necessarily, but the component and D-terminal cables that carry the RGB signal on NTSC consoles are exorbitantly expensive thesedays).

pr0ton, what you've posted is essentially the same image that I referenced in my first post. The LM1881N will turn the RGB signal into RGBHV, which is what is used with VGA - I think there are threads floating around from people who have tried just that, but the results weren't pretty.

Would love to hear more from Jorge Nuno on how the lines can easily be read at double speed to match the sync rate. I'd be willing to put quite a bit of time into playing around with this, but unfortunately I won't have access to anything I can test out until after the Christmas period.

 

Component cables are very rare indeed. Modification of the component cable to RGB would give 480p, someone managed to do this:

BUT, forcing 480p (and NTSC) is possible on a PAL cube, even with a soft-mod in combination with a GCOS (Edit: well, at least with a soft-mod you are able to run a GCOS). I am also convinced that the PAL cube won't give a 480p over RGB (scart), due to hardware restrictions. As (most?) VGA ports needs a progressive signal, 480i to 480p needs to be done? This is expensive.

In other words, does a Qoob Pro mod chip for example really give a 480p signal in a PAL cube (over RGB scart)?

I know, I already made a note for this: I am trying to make a converter too, with the SCART-cable, and found some images that worked for people on DVD-players (same schematics as OP).
Only making a SCART convertor would be a bit easier perhaps..

Could be due to 480i (while 480p needed)?.

 

Hmmm... in this case it could be a lot trickier than just converting RGB to VGA. There's a lot of topics on forcing PAL Gamecubes to 480p, but this can only be done via component leads, which can easily be converted to VGA leads anyway.

One thing I may have been wrong on was the notion of using NTSC consoles, as the digital out port is just that and outputs YCrCb, which is then converted by the DAC on the component and D-terminal leads. Macronix and Nintendo have released no information on the DAC and it's apparently ASIC, so differs from the standard ones they use.

Basically, it simply boils down to whether it's possible to convert a 480i or 576i signal to 480p, which in itself wouldn't be easy.

 

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You need an ADC to convert the RGB to digital, a RAM to store the incoming lines, a DAC to convert them back to analog and a programmable logic device to do the signals (and controlling the rest of the components), and optionally a pixel clock regenerator.

I'm doing a video scaler myself for any system (and even arcades maybe upto 30kHz) and doesn't need to have RGB: SVideo/Component/Composite decoding is planned. But forget about "off the shelf" stuff, the components are indeed buyable but the VHDL code doing the magic is not..

I have a blog about it, but it's offline at this moment for some reason.. Regardless Ill leave this here:


Sorry for deforming the forum layout :|

 

Yes, indeed, that's the question. I'm trying to find if a modchip with Force 480p (Qoob Pro), would give us the correct signal. But I'm afraid the video chip of the PAL Cube will never allow to give us 480p over RGB (Scart).. :crying:

 

This is indeed the case. The more I read on the subject, the more I realised that it wouldn't be anywhere near as simple as the original image I found suggested. And Jorge's last post ultimately confirmed so(edit: btw, that project looks great so far)

 

Thanks

Also, here you have a "simple" line doubler:
http://elm-chan.org/works/sc/report.html ;-)

Beware though, monitors may reject 50Hz Vertical syncs, since this is a PAL console we're talking about in this thread and a line doubler can't do anything about it.

 

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It's far too large to even bother with. Just buy one of these and split the sync signal: http://www.ebay.co.uk/itm/170717102...X:IT&_trksid=p3984.m1438.l2648#ht_3132wt_1020

 

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The picture on Ebay even shows a 8-pins (RGBS) connector! Does this mean the 'S' stands for composite-sync and there isn't a splitter needed?

http://retrogaming.hazard-city.de tested this (sort of) device(s) and says there is only a little lag. Overall, they are very positive about it! Think will go with such a device, as there are no big probems with it?

Edit: Yes, the 'S' accepts the composite sync, so there is no LM1881N needed: youtube. I will set this doubleliner/scaler up with this cable, as I don't want to cut in the original Nintendo cable.
Maybe Jorge Nuno can tell us if his DIY solution has less lag and better quality (as there is no scaling involved)?

 

My own scaler will have a lag of about 30 video lines maximum, dependent on the selected output resolution (this number is for 1920x1080). A 640x480 output res would have a lag of about 1 line. Independent if the source is interlaced or not.

But my scaler (assuming I'm going to sell it) is much more expensive than that. One thing about it is that the user can configure EVERYTHING and per system using an IR remote (any one, it auto learns), since it's all FPGA based, and a generous size one at that :flamethrower:

BTW, this is my scaler blog http://247server.net/~jorge/?p=1 still haven't updated it with the lastest news, oh well...
Also, for more background info: http://www.sega-16.com/forum/showthread.php?13780-Genesis-does!...-1080p

Sorry for the thread hijacking :|