Monday, January 18, 2016

The Quest for Better Video Quality, Part 1

Gaming with any system before a Dreamcast (with its fantastic VGA output) on a modern TV really sucks. Everyone has seen nice crisp colorful screenshots from emulators. Why bother with old systems? Why not emulate? That's no fun, emulation is inaccurate and some games actually play incorrectly with segments you can't pass because of timing differences. What about a Retron? Well, that's an emulator too.

So, how do we get a great picture out of an older console on an HDTV? Sure, you can just get an old CRT... but composite video is still shitty. Well, then you can step your game up, buy a PVM, get some SCART cables and break out the RGB and sync signals and have the absolute best presentation for an old console that's possible. Barring that, you can drop about $300 on an XRGB and upscale everything and add scanlines and output it all through HDMI. 

So, you've got some options there. They're options, but they'll cost you. I've looked for a good CRT for a long time with no luck. I haven't even come near finding a PVM locally, and I don't really want to have someone across the country ship me a PVM from eBay. The CRT TV is the cheaper option than an XRGB. I never even considered that, spending $300 on a video scaler is fucking bonkers. So, hope has been lost. Until I found out about this:

A $25 video scaler (the Gonbes GBS-8220) made by our enterprising Chinese friends that can be modified to accept an RGB signal. Undoubtedly the quality won't be AS good as an XRGB, but for a fraction of the price I think we can accept some quality loss. I've priced everything out at $70 (including parts needed to make a sync stripper and a scanline generator, not including any needed SCART cables for consoles), which is less than I'd likely end up spending on a decent CRT as well. The only knock on this solution for some may be that it outputs VGA - the HDTV I have does have a VGA input, so it honestly makes no difference to me.

Why is it so hard to get a decent picture out of older systems? What the fuck is SCART?

Well, those composite video cables combine all of the picture data on a single cable. Colors don't come through as well, you get bleeding, you get all kinds of nasty shit. Composite carries all of the color information, all of the sync information, all of the information to make up the actual picture.. That's a mess. 

SCART is a standard mostly used in European countries, and it was basically a one cable does all solution similar to HDMI. SCART RGB breaks out the video signal into red, green and blue channels (but it is NOT the same as component) with the signal needed to synchronize the separate channels separated out as well. This results in much truer colors and better overall image quality.

Stolen from RetroRGB because it's a fantastic example

You can scale composite video, but it's still going to have the same lacking colors, etc. This is why the gold standard is RGB. Since US TVs don't have any way to accept RGB natively (for the most part, some CRT TVs you can modify the chip providing the on screen display for channel info and feed it RGB directly), that's why we need some hardware acting as the go-between. 

This is how we'll connect an RGB source to the scaler. The sync stripper is necessary as the board expects h-sync and v-sync to upscale the source signal. It's a very simple process for what you're getting in the end.

The other thing you'll want (this is really more of a preference type of item) is a scanline generator. This may seem unnecessary or even that it would degrade the image to some, and I don't think that's an incorrect stance to take. Why are scanlines desirable, though?

Well, CRT TVs displayed 480i images. If you're not up on your video standards, an i after the vertical resolution means the image is interlaced, and p means progressive. An interlaced image is essentially two signals which is stitched together to make one image. There's a signal of even lines and a signal of odd lines, which is combined to make one image. Older consoles actually didn't output interlaced signals. They output at 240p, which you can think of as half of a 480i image (so, either the odd or even signal). Since the TV was, in a sense, getting half of an image the lines which weren't present were simply blanked.

Since the scanlines are really being added as an aide to simulate the feel of how we would have seen the game, well, that's why I call it a personal preference item. 

Basically every major system can output RGB over SCART - the Super Nintendo, Sega Genesis (and its add on tumors, the 32x and the Sega CD), PlayStation, Saturn, even up to the PlayStation 2 and Dreamcast (though the PlayStation 2 and Dreamcast are better served with component and VGA respectively). The NES has an add-on board which you can purchase to output RGB and the Nintendo 64 can as well (some models with a simple signal amplifier, others with a rather expensive add on board which must be soldered very carefully). So, if you're tired of composite on an HDTV and you want some better video, a modified GBS-8220 seems to be your solution. I haven't yet received mine, but I will make a follow up post when I do.

I'll also note that I've left out some other "easier" options. In particular, there is a straight SCART to HDMI converter that's available on eBay for about $30. This is a very easy and cheap solution, though it's prone to a somewhat smeared look and shimmering around objects.

1 comment:

  1. Fucking great stuff here, man. I really enjoyed this read.