Anyone know how to build a "VGA out" to a "component in" box?

[Frigo]

More precisely: VGA ---> BOX ---> Component ---> TV.

Diagrams, instructions, pity; I'll take anything. I'm moderately competent with electronics, but can't read a diagram without some help. Thanks!

[BobA]

Depends on your video card.  Some ATI cards just need the proper adapter that will not work on other video cards.

[Frigo]

I was actually thinking of pulling R,G,B,Sync,Ground, etc signals from a video encoder chip like the CXA1145 (common in older video game consoles) and feed it through some sort of circuit to convert it to component.

[MonMotha]

There are two things you need to handle: colorspace, and sync.  Remember, RGB (aka "VGA") is a component video format, it's just in a different colorspace than what most TVs with "component" inputs expect.

Colorspace is just a bunch of analog electronics.  Basically, you need some summers/differencers to handle the RGB to YPbPr matrix. http://circuits.linear.com/158 is a handy app note from LT that might work.  There are several other ways of doing it, too.

The other difference is sync.  PC outputs have TTL level, separate sync.  YPbPr has composite sync on Y.  An XOR gate (or several combined with some suitably sized RC networks for auto-polarity handling) can get composite sync from the separate syncs.  Then you can use a transistor or similar to dump sync onto the Y line.

All that said, why build one?  You can buy a pre-made one for like $20-40, and you won't have to futz with it.

You WILL need to feed the box video timed suitably for your TV.  640x480 "VGA" is compatible with 480p aka "EDTV".  If you want standard def, you'll have to output either 320x240p or 640x480i (interlaced).  Various methods can get this from your PC e.g. Soft15kHz if you run Windows or some suitably chosen modelines on Linux.  HD modes will usually work, too, so you have have 720p, 1080i, or even 1080p if your TV supports it.  Check compatibility with your desired resolution on any box you buy.

You can't use a CXA1145 for this.  It does not expose the unmodulated chroma components (which would be I/U and V/Q, very closely Pb and Pr) outside the chip.  It just has the modulated chroma signal used for S-Video (though the luma "Y" signal is present).  FWIW, CXA1145s can be hard to find now.  Analog Devices makes a similar chip with P/N AD725.  Rohm also makes one that's used on the popular cheap China-made "RGB to S-Video" adapters.

[Frigo]

There are two things you need to handle: colorspace, and sync.  Remember, RGB (aka "VGA") is a component video format, it's just in a different colorspace than what most TVs with "component" inputs expect.

Colorspace is just a bunch of analog electronics.  Basically, you need some summers/differencers to handle the RGB to YPbPr matrix. http://circuits.linear.com/158 is a handy app note from LT that might work.  There are several other ways of doing it, too.

The other difference is sync.  PC outputs have TTL level, separate sync.  YPbPr has composite sync on Y.  An XOR gate (or several combined with some suitably sized RC networks for auto-polarity handling) can get composite sync from the separate syncs.  Then you can use a transistor or similar to dump sync onto the Y line.

All that said, why build one?  You can buy a pre-made one for like $20-40, and you won't have to futz with it.

You WILL need to feed the box video timed suitably for your TV.  640x480 "VGA" is compatible with 480p aka "EDTV".  If you want standard def, you'll have to output either 320x240p or 640x480i (interlaced).  Various methods can get this from your PC e.g. Soft15kHz if you run Windows or some suitably chosen modelines on Linux.  HD modes will usually work, too, so you have have 720p, 1080i, or even 1080p if your TV supports it.  Check compatibility with your desired resolution on any box you buy.

You can't use a CXA1145 for this.  It does not expose the unmodulated chroma components (which would be I/U and V/Q, very closely Pb and Pr) outside the chip.  It just has the modulated chroma signal used for S-Video (though the luma "Y" signal is present).  FWIW, CXA1145s can be hard to find now.  Analog Devices makes a similar chip with P/N AD725.  Rohm also makes one that's used on the popular cheap China-made "RGB to S-Video" adapters.

Wow, that sounds like a lot more than I'm ready for. Isn't there any way to pull the signals from the encoder chip and feed it to a pre-made box without having to go through the hassle of getting a scart cable/converter (which isn't in my budget at the moment)? Also, where would one go to find a pre made box if this were possible?

[MonMotha]

I'm not sure how what you're talking about even makes any sense.  What is your signal source?  Why do you need a SCART cable?  Why are you talking about "pulling signals from an encoder chip"?  Do you already have one of those chips in a circuit somewhere you're wanting to chop into?  The CXA1145 (and AD725, and the Rohm part) are all pretty monolithic: RGB in, and either composite or s-video (Y/C) out.  They do not make the Yb and Pr signals (which are interim steps to getting the "C" in Y/C s-video) available outside the chip.

Premade boxes to do this are all over the place.  They are often sold under the term "transcoder".  I see them on ebay with some frequency.  You can also just look under "RGB to YPbPr" or "RGB to component" (even though the latter is somewhat of an unspecific, misused term, it's very common).  Check google.

[Frigo]

Ok, I want to do this:

http://www.youtube.com/user/phonedork#p/u/13/cOhntr-4xx0

without spending a whole lot of this:

 

[MonMotha]

No flash, sorry, so I can't watch Youtube.

However, articles on the subject indicate that you either get S-Video or RGB out of a genesis.  You'd need an outboard colorspace converter if you want YPbPr component.  Just buy a box. If you're not skilled with this, you'll easily spend hours building and debugging it all to save maybe $20.

If you really want to build it, that LT circuit I posted should work.  They have a suggestion for how to handle putting sync on Y (350 ohm switch to -3.3V, aka use a MOSFET or transistor and a ~350 ohm resistor).  You'll probably need AC coupling caps since the genesis probably has DC offsets on its video outputs.  0.1uF ceramics inline with the incoming video signals between the 75 ohm termination resistor and the op-amp inputs should do nicely.  You can build this on a single ~6V supply if you wish: just generate a false ground at 3V using a resistor divider and an extra op-amp wired up as a buffer and tie pin 4 of the left triple set to that false ground.  AC coupling caps in the input (and outout) are then mandatory as your circuit would expect "black" to be at 3V.

You can potentially save yourself the expense of the Genesis SCART cable by hacking the end off a PC VGA cable and soldering the wires directly to the connector on the inside of the console.  As a suggestion, use a cheaper cable: they tend to just have discrete wires rather than mini-coax, and so they'll be easier to deal with.

The cheapest option would be to hack the end of an s-video cable and solder it directly down to the appropriate places giving you a genesis with an s-video "tail".  S-Video is almost as good as YPbPr component at standard def on a quality TV.

[mvsfan]

Okay, this is somewhat related, but not completely. Does anyone make a device to properly up convert old devices like a Snes, so it looks good using the analog inputs on a new hdtv?

thankfully i still have old tube tvs that people gave me. Old video game systems look horrible using the analog inputs on a flat screen.

[Samstag]

Okay, this is somewhat related, but not completely. Does anyone make a device to properly up convert old devices like a Snes, so it looks good using the analog inputs on a new hdtv?

thankfully i still have old tube tvs that people gave me. Old video game systems look horrible using the analog inputs on a flat screen.

Having a few beers before you play will give you that CRT look on an LCD TV.  Or smear some vaseline on a pair of sunglasses.

[MonMotha]

The issue is that the scalers built into televisions are designed for photorealistic images, not blocky pixel art like used on old-school video games.  The upconversion blurs the heck out of the edges to try to make it "smooth" when, for pixel art, this is just about the most wrong thing you can do.  There are actually special scaling algorithms out there just for scaling up pixel art, and I think MAME supports some of them, as well as some old console emulators, so simply using an emulator with upscaling to the native resolution of your TV is probably the easiest and most cost effective solution.

An outboard scaler could be developed that implements these scaling algorithms to allow plug and play operation with a TV and an actual old console.  I'd offer to do it for you (I know how), but it's probably not worth it either in time or what it would end up costing you.

[mvsfan]

The issue is that the scalers built into televisions are designed for photorealistic images, not blocky pixel art like used on old-school video games.  The upconversion blurs the heck out of the edges to try to make it "smooth" when, for pixel art, this is just about the most wrong thing you can do.  There are actually special scaling algorithms out there just for scaling up pixel art, and I think MAME supports some of them, as well as some old console emulators, so simply using an emulator with upscaling to the native resolution of your TV is probably the easiest and most cost effective solution.

An outboard scaler could be developed that implements these scaling algorithms to allow plug and play operation with a TV and an actual old console.  I'd offer to do it for you (I know how), but it's probably not worth it either in time or what it would end up costing you.

no, i dont think it would be worth the time.

Ive got 5 tube tvs im currently not using, and ive got a 40" upstairs thats hooked to my consoles.

I had bought a 52" HDTV as a replacement for the 40" tube, and when i realized what i was in for with games, i put the 40 right back in its spot.

Im currently using the brand new hdtv as a computer monitor though i do have them in all the other rooms for directv.

[BurgerKingDiamond]

hmm. I'm not sure about this at all, but I know that Component cables are misleading. Even though they are colored Red, Green, Blue, component cables are not truly R,G,B. I looked it up one day, it's some other colorspace. So I don't think you can just pull the R,G,B signals from VGA and then amplify them... But I'm no expert.

[Frigo]

hmm. I'm not sure about this at all, but I know that Component cables are misleading. Even though they are colored Red, Green, Blue, component cables are not truly R,G,B. I looked it up one day, it's some other colorspace. So I don't think you can just pull the R,G,B signals from VGA and then amplify them... But I'm no expert.

Nope Y (green) carries Luma and sync signals like 1/2 of an s-video cable. Pb (blue) carries the difference between blue and luma, and Pr (Red) carries the difference between red and luma. The TV takes all that info and figures out what green is based on those signals. That's why a converter is needed from RGB to Component. I think I'll just end up buying a converter box - there isn't enough info out there for me to build one on my own.

[boykster]

I don't remember if / how well it worked, but there was a DIY  VGA->component thread on AVS many moons ago

http://archive.avsforum.com/avs-vb/showthread.php?threadid=193919

Here's a link to the article referenced by the OP

http://www.keohi.com/keohihdtv/interfaces/diytranscoder.html

and to the schematic

http://www.keohi.com/keohihdtv/interfaces/diytranscoder_johrhees.html

You might skim that thread to see if anyone successfully built one before spending too much time down this avenue.  Considering how inexpensive they converter boxes are these days, I'd just buy one.