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The ExtraLives.org Guide to Capturing and Streaming Video (On a Budget) Part 2: Dot Crawl and Rainbowing

The object of this guide is to get the best possible video quality for the lowest amount of money. While we've gone over how to fix the whole interlacing problem in the last article, why stop there? You can make your video look EVEN BETTER with a few easy steps. Oh, and it's worth pointing out most of these fixes won't cost you a dime.

There are two other issues that tend to crop up when capturing standard definition video with plain-old, "probably-came-with-your-console" composite cables.

Dot crawl (AKA: "That Checkerboard Pattern Along the Edges")

...and...

Rainbowing (AKA: "Where did these other colors come from?")

Read on for more information on these two video defects and how to take care of them!

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You'll probably come across both of these issues if you capture video with composite cables and only composite cables. There's a reason for this-- composite cables carry video only over one wire that carries chroma (what color the picture is) and luma (how bright or dark each color is). With these two together, you're able to recreate most every color in video.

Only problem is that carrying both of these on the same wire results in some interference between the two, resulting in some pretty odd quality issues.

One of these defects is called dot crawl. You can see dot crawl on the edges of images with large color differences. Using Wind Waker as an example (again)…

Look at where the wall on the left meets the sky. See that checkerboard pattern all along the edge? It's present in a lot of this image from Link's head to the pirates' bodies to the item buttons-- that's dot crawl. Aside from just wrecking all your nice, well-defined edges, in motion, the checkerboard pattern also flickers back and forth.

While not nearly as large a quality issue as interlacing, it's still worth fixing. Hey, we want out video capture to look as great as it can be, right?

The problem is exacerbated when two very different colors meet up at an edge. In Wind Waker, this amounts to a whole lot of dot crawl when you're near the ocean (and given just how much ocean there is in Wind Waker, well… we've got a problem on our hands).

There are two ways to fix this problem and because we're cheap, we'll go through the free method first. There's a certain filter in VirtualDub that will help here. There's nothing in Xsplit (or any other streaming program that I know of) that'll fix this for you. You're going to use what's called a "comb filter." Unlike our solution for interlacing, this filter isn't built into VirtualDub-- you'll need to download it here (made by this guy!).

Once you download the plugin, navigate to wherever your VirtualDub filter is and dump the dotcrawl.vdf file in the "plugins" folder. Just as we did to deinterlace the footage in VirtualDub, click File and then "Capture AVI." Then click video, preview acceleration and select "Progressive - both fields."

From here, make sure "Preview" is selected and then click "Filter list…" You should have a new filter there called the "DotCrawl Comb Filter."

Click "OK" and then a box with settings will pop up.

The default settings seem to generally do the job so just leave everything checked as-is and click okay (your input and output sizes may vary, don't worry about that).

And now… the dot crawl is gone! All the edges are smoothed out and everything looks a whole lot better and clearer than before.

Remember how much dot crawl was mucking up this close-up before? With the filter on, you can barely see any of it remaining. Not bad, huh?

Still, this method has one flaw-- when an area of an image changes color quickly, some odd coloration can pop up. Because the filter eliminates dot crawl by averaging information from a few frames in a row, some of the image in those older frames might inadvertently end up in a frame where they don't belong.

I spun the camera around in a circle to produce the screenshot above. See how there are some random bits of white from the clouds and blue from the sky in the wrong places? That's the biggest flaw to this method of eliminating dot crawl. Still, frames like that one there are shown for a small fraction of a second. Moreso, they only occur when there's a large change in color which is why there are no similar problems anywhere else in the shot.

Essentially, we can eliminate dot crawl for free using VirtualDub and the special comb filter. While it might cause some minor video glitches, it's generally pretty effective. But say, for example, you want absolutely no problems and are willing to spend a few dollars to make this happen.

There's another fix for this and it involves purchasing an S-video cable. I'll go more into the differences between composite video and S-video in a different article. For now, remember how I said the chroma and luma info was carried on the same piece of wire in composite cables? Well, S-video (the "S" stands for "seperated") has these bits carried on different wires in the cable. This means there's no interference between the two and also means you get a much sharper image. With not dot crawl. That's good.

The same shot of Wind Waker as we were looking at earlier… but taken using an S-video cable! No filters of any sort (aside from a deinterlacing) are on. Now this looks great-- you can even see the individual lines of pixels at the top of Link's head if you look closely. The only real problem in using this method is that S-video cables are pretty uncommon. Nobody really includes them in the box and I've never owned a standard-definition TV that accepted S-video input. 

Still, you shouldn't go broke buying one-- the GameCube S-video cable I used here cost me a mere $4.99 on eBay with free shipping.

And, of course, there's no dot crawl.

That about sums up fixing the issue of dot crawl. If you're cheap, you can fix it for free using a special filter and VirtualDub. If you have a few bucks to spare, you can shell out for an S-video cable and eliminate it without any computer trickery (and get much sharper video quality too).

There's one other issue related to dot crawl that we can also fix using similar methods. Remember how interference between chroma and luma signals in your standard composite cable made dot crawl? Well, it also causes a thing called rainbowing. Rainbowing is exactly what it sounds like-- a bunch of random colors that shouldn't be in an image somehow end up on the screen.

It's certainly not a major problem but we might as well take care of it. Rainbowing is uncommon in many modern games but certain kinds of text (white on blackor vice versa) or older NES-era games tend to really suffer from it the most.

The text in the only thing I use the Wii for anymore/illegal game footage/other strikethrough'd word image above above should be just white. So what are all those colors doing there? Similar to dot crawl, the colors tend to flicker back and forth so it's best to eliminate rainbowing if you want the clearest footage you can get.

Thankfully, that comb filter we downloaded and used for eliminating dot crawl also works to eliminate rainbowing. No extra work involved-- you can even leave the settings alone.

Here's another example. You might remember this weird recreation of Windows 98 on the NES from our Bootleg Bonanza Marathon in August, 2011. In addition to being really janky, it's also got some horrible rainbowing on all the text.

…but with that filter applied, the whole thing becomes much clearer. Now you can look at Chinese Windows 98 help screens on your NES in perfect clarity.

Rainbowing effects more than just text. A lot of older games tend to have this issue as well, even when there are no words in the way.

Those houses and the floor in Zelda II should just be brown. While rainbowing makes everything a tad funkier, the random red, green and blue lines really shouldn't be there.

Let's just turn that filter on and… hey, wait a minute! It's not any better!

What do we do now? Sadly, there's nothing else you can do for free, really. No matter how much you fiddle with the settings, the rainbows will live on. Using plain old composite cables, you're stuck with an image that looks like this. If you purchase some S-video cables…

BAM. Not only are the colors are exactly as they should be but the image itself is a whole lot sharper.

Maybe the filter not working with Zelda II was just a fluke? Do all old games have that same sort of issue? As you can see, the grey blocks in Super Mario Bros. 3 suffer from a bunch of rainbowing. Let's just put that filter on and…

Nope! The rainbows on the blocks are still there. Not only that, but now it seems like there's some odd optical illusion where the screen looks like it's been tilted to the side slightly.

So not only did our filter not work but it made the image look even worse. Seems like the filter has a few limitations in that it only really works reliably well with cleaning up blurry or miscolored text.

As before, the only solution here is to get a set of S-video cables…

…which makes the image look a lot sharper and corrects all of the colors too.

 

So essentially, with just an extra step or two, you can clean up some of the video you capture so when you broadcast it, it'll look as good as it can possibly can. Your viewers will appreciate it (and if they don't, ban 'em-- good riddance).

Keep checking back as I add more parts to the Big ExtraLives.org Video Streaming Tips Supreme Guide Thing! Be sure to leave a comment if there's something specific to video streaming or capture that you'd like me to go over.

Comments

Whenever I play video games with an S-video cable I'm just better! All my friends have stopped laughing at me because I suck at games! Buy an S-video cable, you won't regret it! S-video cables can be found in the medicine aisle.

Thanks for this Extralives team. This really helps for when I don't want to record using Emulators. I just hope the TV that I will use when I start doing that in the future has a slot for an S-Video cable. Or I am able to do all of the other things that you talked about.

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