I think the RGB sync on a PCE is 31KHz? I'll have to check when I plug into my LCD monitor it will display the current H/V sync rates
Nope. 15.7khz like other consoles and arcades of the time. 31khz would mean the pixel output rate itself would also have to be twice as fast as well. It's not.
The composite from the Duo line is good enough that it's actually acceptable in my book. The Duo (and entire Grafx line, for that matter) has some of the best stock composite of any vintage system.
My biggest issue with composite in general is the rainbow effect you get on dithered parts of the picture. If I could somehow eliminate this rainbow effect then I'd have zero issues with the Duo's composite.
TVs with better filters will the remove the rainbowing from PCE/TG16 games, but the 'dot-crawl' like artifacts will be there for most motion/scrolling in a game. S-video would your best bet then, if you didn't want to go the route of RGB.
I see this logic used a lot as an anti-RGB argument. If it were true however, nearly every arcade game ever made wouldn't have used RGB. I'm not saying that there aren't games out there that took advantage of composite's ability to naturally dither graphics, but the vast majority did not. Games just plain look better in RGB, from the sharper picture to the brighter colors. That doesn't mean that they don't still look very good in composite, especially from a system that outputs a good composite signal.
I don't know about you, but I spent a lot of time in the arcades. Yeah, they used RGB CRTs, but they still weren't as sharp as what every is seeing today on there RGB mods and setups. Those displays BITD still had some analog pixel interpolation.
My only problem is that it sharpens the pixels a bit much. Most older game systems assume a certain amount of video blur and quality reduction, and sometimes the sharpness bites back. It's like using uber-fancy headphones with MP3s. Beyond a point they actually worsen the experience because they highlight the encoding flaws.
You
can add analog filtering back into the RGB setup (for horizontal pixels only). As long as you do it to the RGB lines and
not SoG line (sync on green).
My only complaint with the RGB setup (I can add the analog filtering back into the signal when I want to, or make a switch for it, whatever) is the wrong color space. All the PCE/TG/Duo's consoles have a specific artifact in the color space conversion. The composite out is more than just simply RGB->YUV conversion that's sent on its way for modulation. There's a lookup table and low precision one at that. The composite out of the system (VCE) is only using 5bit DACs. That's 15bit color space total (32k colors). You need quite a bit of precision to go from RGB to YUV (even 8bit for 24bit output isn't enough). This internal table gives a bias to certain color ranges (hues as well as brightness) and makes the color palette of the PCE unique. Tapping the RGBs, you
completely bypass this. I've been noticing that some games look
better in this custom color space than in pure RGB (disregarding anything else).