RGB YPbPr conversion

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Alphathon
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RGB YPbPr conversion

Post by Alphathon » Fri Mar 12, 2010 4:59 am

Hi all. I've visited these forums a few times and find the discussions really interesting, but I've never posted anything before.

Here's the deal. I want to get the best possible video signal from all of my consoles, and for the most part that's simple - PS3 and Xbox 360 by HDMI and PS2 by component (YPbPr). Unfortunatelly, that leaves the GameCube. I have a PAL GameCube which gives it composite and RGB SCART out, as well as the digital out, which is capable of component, but requires the rediculously expensive Nintendo component cable (they're currently selling for upwards of £50 ($75 US) on eBay, mainly because they were never released over here, so are all originally imports). Now, other than the lack of progressive scan (which is pretty irelevent anyway as all my games are PAL and don't support 480p), the RGB output should technically be capable of the same quality as the YPbPr from the digital out, so I'd like to use it. The problem? I have no SCART inputs on my setup (Sony AV Receiver connected to a PC monitor by HDMI), only HDMI, YPbPr and Composite, so what I want to do is convert the RGB into YPbPr. The other two options are get a Wii (can't really afford it) or buy a commercial converter (which tend to cost more than the comonent cables :? probably 'cause it's a niche product)

Logically speaking, this doesn't seem like a terribly difficult task, and I have seen circuits for VGA->YPbPr conversion which look pretty damn simple, and presumably the sync conversion wouldn't be required as SCART and YPbPr both use composite sync rather than separate H- and V-syncs, so no conversion would be required...at most a composite sync stripper to remove the video signal. Here's an example:
Image

Basically I was wondering if this could be adapted to convert the RGBs to YPbPr. I know enough about electronics to basically understand what's going on, but not enough to tweak the values to adapt it. I would assume the sync wouldn't need to be changed as it isn't being deinterlaced or anything (keeping the resolution, format etc, just changing the encoding), so its simply a case of converting the colour info to luma and difference signals and combing the sync with the luma signal.

Thanks in advance.

N.B. The site that I found that schematic on notes that the resistor by the Y connctor should be 75 Ohm, not 1k

Alphathon
Posts: 10
Joined: Fri Mar 12, 2010 4:02 am
PSN Username: Alphathon
Steam ID: Alphathon
Location: Scotland, UK

Re: RGB YPbPr conversion

Post by Alphathon » Sat Mar 13, 2010 11:39 am

OK, I've re-done the diagram. Will this work?

EDIT: [IMAGE REMOVED]

OK, I've found another schematic which is designed specifically for RGB SCART, so I'll use that instead (see below). One thing though, is the video DC coupled? (If it is then part of the circuit can be ommited). Judging by what I've read on Wikipedia it is AC coupled (by the fact that standard RGB SCART cabled require capacitors on the R, G and B lines) but I really don't know much about this.
http://elm-chan.org/works/yuv2rgb/rgb2yuv.png

Alphathon
Posts: 10
Joined: Fri Mar 12, 2010 4:02 am
PSN Username: Alphathon
Steam ID: Alphathon
Location: Scotland, UK

Re: RGB YPbPr conversion

Post by Alphathon » Mon Mar 15, 2010 3:02 pm

OK, after having looked at the schematic posted previously, I have drawn up a new one which shows all paralell resistors (rather than their combinations), uses IEC symbols (rather than American ones - I live in the UK, so thats what I prefer), and shows the amps, sync stripper and multiplexer as chips rather than circuit symbols. I've never used ICs before, only wires, resistors, the odd capacitor and output devices (speakers, LEDs etc)...and batteries/power of course, so I wanted to make sure I was understanding everythings right. Have I done it all right (especially the decoupling capacitors - I've pretty much just guessed what to do with them by looking at the first schematic)?

Cyan parts are just to identify power supply sections. I have omitted the actual power supply.

Image

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Tighe
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Re: RGB YPbPr conversion

Post by Tighe » Mon Feb 17, 2014 10:31 am

Alphathon wrote:OK, after having looked at the schematic posted previously, I have drawn up a new one which shows all paralell resistors (rather than their combinations), uses IEC symbols (rather than American ones - I live in the UK, so thats what I prefer), and shows the amps, sync stripper and multiplexer as chips rather than circuit symbols. I've never used ICs before, only wires, resistors, the odd capacitor and output devices (speakers, LEDs etc)...and batteries/power of course, so I wanted to make sure I was understanding everythings right. Have I done it all right (especially the decoupling capacitors - I've pretty much just guessed what to do with them by looking at the first schematic)?

Cyan parts are just to identify power supply sections. I have omitted the actual power supply.

Image
Did you ever get this working? I need to do the same thing.

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Tighe
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Re: RGB YPbPr conversion

Post by Tighe » Mon Mar 03, 2014 6:33 pm

I ended up doing this:

http://www.youtube.com/watch?v=b82kFVTn8y4" onclick="window.open(this.href);return false;

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