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Re: So.... Some SNESes output YPbPr.....

Posted: Mon Jul 02, 2012 7:55 pm
by getafixx
So i tried using the NPN transistors idea and used S9014-C331 x2. Made a huge difference, as now the colors were not washed out anymore.

I tried it with the 1K resistors at first, but it actually didnt look as good as it did without them (it was darker with the resistor installed). So i left them out of the loop.

Re: So.... Some SNESes output YPbPr.....

Posted: Mon Jul 02, 2012 8:17 pm
by elmagicochrisg
getafixx wrote:So i tried using the NPN transistors idea and used S9014-C331 x2. Made a huge difference, as now the colors were not washed out anymore.

I tried it with the 1K resistors at first, but it actually didnt look as good as it did without them (it was darker with the resistor installed). So i left them out of the loop.

So you used these transistors on the Pb and Pr lines?...

Re: So.... Some SNESes output YPbPr.....

Posted: Mon Jul 02, 2012 9:27 pm
by getafixx
Yeah, without the resistors. Y is running from the multiout pin 7.

Re: So.... Some SNESes output YPbPr.....

Posted: Mon Jul 02, 2012 10:58 pm
by elmagicochrisg
getafixx wrote:Yeah, without the resistors. Y is running from the multiout pin 7.

Thanks... ^^

I'm having a hard time understanding the logic behind it though.

Just a few random thoughts. Correct me if I'm wrong please...

The transistor on B boosts B minus Y, not just B.
The transistor on R boosts R minus Y, not just R.

Fact that the transistors boost the blue and red signals minus Luma, and not just the blue and red signals, means both blue and red output stay pretty much the same.

Green is more saturated because of the transistors on both the Pb and Pr lines.

Boosting or restricting Y only affects brightness and the green signal, not the blue and red one.

Is there a formula to calculate the green signal?... I think knowing that is essential to understanding what's going on here...

I hope I've got some of that right. If not, please enlighten me... :P

EDIT:

Shit. Just reread my comment, and... it doesn't make sense at all... :lol:

Found this on Wikipedia though:

While luma is more often encountered, (photometric) luminance is sometimes used in video engineering when referring to the brightness of a monitor. The formula used to calculate luminance uses coefficients based on the CIE color matching functions and the relevant standard chromaticities of red, green, and blue (e.g., the original NTSC primaries, SMPTE C, or Rec. 709). For the Rec. 709 primaries, the linear combination, based on pure colorimetric considerations and the definition of luminance is:

Y = 0.2126 R + 0.7152 G + 0.0722 B

I guess that's the best place to start explaining how everything works?...

Re: So.... Some SNESes output YPbPr.....

Posted: Tue Jul 03, 2012 3:15 pm
by getafixx
Ok, well my understanding of this is that when tapped from Pin 7, Luma is higher than the other 2, so it causes the picture to have a "washed out" effect. By adding transistors you are basically "boosting" Pb and Pr so that they are as close to the same level as the Y as possible. i read over in Ace's post on Sega16 that he used 2 NPN transistors and 2 1Kohm resistors. He recommends later on using the C945 NPN transistor type, which i didnt have any on hand so I substituted the one i used. So that's where I got the info for all this.

As for all your technical info, i really couldnt say. I dont know any calculations for all this :P.

Re: So.... Some SNESes output YPbPr.....

Posted: Wed Jul 04, 2012 7:06 pm
by bernhs
It is necessary to try also the ground of the video card "pine 6" /12. Because it is more suited.

Re: So.... Some SNESes output YPbPr.....

Posted: Sun Jul 15, 2012 7:54 am
by Drakon
bored_index wrote:oh of course...in THIS thread on racketboy it is your suggestion and on sega16 it's Ace's. sure you could say it is both of yours idea if the both of you corroborated and brainstormed this suggestion together. but evidently, based on timeline and the overall modding community (to include all modding site/forums) as a whole, Ace suggested it first, so it's Ace's suggestion #period/#shutdown/#gameover


I didn't get the idea from ace so it's my idea just as much as it is his.

Re: So.... Some SNESes output YPbPr.....

Posted: Sun Aug 05, 2012 7:05 pm
by marvelus10
Im curious as to how many of you guys went ahead with the resistor/amp mod for this, and what encoder chip you have etc.. maybe some brief detail as to each ones personal experience.

thank you

Re: So.... Some SNESes output YPbPr.....

Posted: Mon Aug 13, 2012 12:07 am
by bernhs
According to this Web site http://gamesx.com/wiki/doku.php?id=av:snes2rgb, you should can be to use the sync composite. hihi

Re: So.... Some SNESes output YPbPr.....

Posted: Sat Aug 18, 2012 2:04 pm
by ApolloBoy
bernhs wrote:According to this Web site http://gamesx.com/wiki/doku.php?id=av:snes2rgb, you should can be to use the sync composite. hihi

What does adding RGB to an SNES mini have to do with this?