Genesis 2 composite/s-video?

Post by **Jubal** » Wed Apr 19, 2006 5:02 pm

say on the site its for us/jp region switch

-Jubal-

Post by **jemsic** » Wed Apr 19, 2006 11:00 pm

I didn't have to cut any metal shielding. In fact, I thought there was plenty of room.

Post by **marurun** » Sat May 06, 2006 9:35 am

lordofduct, you are somewhat incorrect. While the Genny doesn't natively output an Svideo signal, it DOES output RGB, even in the US where we don't use it. It's quite simple to convert an RGB signal to Svideo if you know how (I don't, but I've seen instructions on-line). RGB is much higher quality than composite and is very close to Svideo, being slightly better but having a similar signaling setup. Do some google searches and you might find what you need.

Post by **racketboy** » Sat May 06, 2006 9:44 am

marurun wrote:lordofduct, you are somewhat incorrect. While the Genny doesn't natively output an Svideo signal, it DOES output RGB, even in the US where we don't use it. It's quite simple to convert an RGB signal to Svideo if you know how (I don't, but I've seen instructions on-line). RGB is much higher quality than composite and is very close to Svideo, being slightly better but having a similar signaling setup. Do some google searches and you might find what you need.

Excuse my ignorance, but can't you convert RGB to Component as well?

Post by **marurun** » Sat May 06, 2006 4:42 pm

Racketboy, probably, but I think it's probably not quite as simple as Svideo. I think analogue component video might be just a little pickier. I don't know component video as well.

Post by **marurun** » Sat May 06, 2006 4:49 pm

Irk! Found this posted in a forum somewhere. I can only assume this fellow knows what he's talking about:

"2) There is no such thing as a component to RGB Cable! Component video has three signals Y (total brightness) Y-R (Y minus Red) and Y-B (Y minus Blue) green is extracted with analog math in the TV. RGB is just that: Red Green and Blue. the two signals are incompatible. conversion requires analog or digital arithmitic."

This means that it's probably problematic the other way around, as well.

Post by **racketboy** » Sat May 06, 2006 5:05 pm

ok -- I guess that makes sense

Thanks for the clarification!

Post by **evildragon** » Sun Sep 24, 2006 3:05 am

hope it's not too late to add, but there is a small simple circuit i found from JROK, and it's an RGB to Component Adapter... RGB to component is easier to do than vice versa...

http://www.jrok.com/hardware/RGBv4/index.html

I'm almost considering getting that for my Genny, but want to see if it's possible NOT too for one of my hacks... ( i noticed some genesis games use the bad composite to simulate translucency or more colors via dithering... )

Post by **lordofduct** » Sun Sep 24, 2006 4:08 am

marurun wrote:Irk! Found this posted in a forum somewhere. I can only assume this fellow knows what he's talking about:

"2) There is no such thing as a component to RGB Cable! Component video has three signals Y (total brightness) Y-R (Y minus Red) and Y-B (Y minus Blue) green is extracted with analog math in the TV. RGB is just that: Red Green and Blue. the two signals are incompatible. conversion requires analog or digital arithmitic."

This means that it's probably problematic the other way around, as well.

Ummm... no I wasn't incorrect.

There is no direct alteration of RGB to any other signal. It requires some kind of conversion via a conversionchip or adder ICs (the conversion chip just has all the complex stuff placed into the chip). There is a way to convert Component to RGB and vice versa. RGB is a completely different signal from composite signals (RF, RCA comp, S vid, component). But rely's on the fact that white is a combination of all colors... hence why R+G+B=Luminance; later gone over in this post.

Compenent is Luminance (Y), luminance minus the Blue signal (Pb), Luminance Minus the Red signal (Pr). Luminance is just Red Green and Blue added up. Component is just Svid with better color correction.

To convert RGB to component you'd first user adder ICs to add up all the Red Green and Blue to create luminance. Then you'd invert the polarity of the Red and blue and add those with the luminance to create 3 signals... THEN you'd have to splice in the sync onto the Luminance as that is where it belongs (and hopefully you aren't using a sync on Green or similar where it is already in the RGB before creating the Luminance signal... because you'd have to take it out before adding it with the inverted Red and Blue).

To go back from Component to RGB you'd now have to first invert the Pb and Pr, you'd then add the inverted Pb to the Luminance to give you Blue. Next you'd take the full Luminance again and add the Pr to it to get Red. THEN you'd have to split the RED and the BLUE into 2 signals each. Send one of each out of the IC board and then add the left over ones together. Invert those signals and add them to the full Luminance to get the left over Green.

Both these tasks need signal multipliers as well because all the splitting would wear out the Luminance signal along the way degrading even more quality. Going from Component via this route instead of a conversion chip is not a good idea as it degrades quality to possibly below composite (not sure, never actually done it... but math says that would be the way of doing it).

As for back to my making svid.

You'd take the RGB and again add them up to get the Luminance again... then you'd have to figure out the hue saturation between the three signals to get your Chroma. This can be done using some capacitors and resistors... OR just put a new composite encoder chip in (which works all the time... not just some times as they even state on the webpage that they used an svid mod based off the NeoGeo Svid mod). A composite encoder chip just takes an unmodulated RGB and sync signal directly from the system and converts them into multiple useable composite signals... composite signals are actually defined as YUV signals (RF, RCA composite, Svid and Component).

The actual figuring of the Luminance is rather mathematical as it is really the Pb and Pr carried together on one signal in adjacent frequencies called "Quadrature amplitude modulation". This is all done because the actuall RGB signal is unuseable by most televisions (those that except Black and White)... this is why YUV was invented; back when they changed TVs over to color they needed it the television broadcasts to stay backwards compatible with the existing B/W TV sets already all over the nation. A B/W TV can just ignore the Chroma signals and just produce the Luminance to give a B/W signal (actually if you only plug the Green cable from component into any composite input on your TV including the standard RCA yellow jack you get B/W). The saturation from the Chroma signal can also be used to create a more detailed B/W picture as it carries the amount of darkness in the picture as well (it is inherent in the signal due to the summation of the RGB signal to get the Chroma).

Downside to the conversion/encoder chips is that it works best with the unmodulated signals... you shouldn't take the RGB fed out of the pins on the Genny or from a VGA 15pin din because they have already been encoded. You should use the signals going into their respective encoder chip.

One last thing before I go. I don't know exactly how that mod works based on the neogeo thing found in that link earlier in this thread. But from the looks of it it seems it is just figuring out the Chroma by applying an inverted Luma signal to the RCA composite signal to mathematically get the Chroma. Good trick... lower quality.

Post by **neohx_7** » Sun Sep 24, 2006 11:05 pm

This guy will mod lots of different systems for different outputs: www.oldschoolgamer.ca