Composite Video on the NES: Why's it so wobbly?

The Nintendo Entertainment System. Is it the platonic ideal of an 8-bit video game system? Well, only because it’s so prominent and successful– it’s actually kind of an oddball in its expandability and design. But there’s something else about it. The picture is a bit… wobbly. Well, over composite video anyway. Let’s dig in and learn a little big more about the nitty-gritty of composite video. Not so mighty now, are you You don't have a video tag support or something? So you can't see this footage of the *Mighty Bomb Jack* title screen? Ah too bad. Mighty Bomb Jack , the most iconic bomb-collection platform taking place in a pyramid for the Nintendo Entertainment System. The title screen here, like a lot of title screens, is entirely static. But here, I’m using my composite-modded system, which just amplifies the video signal coming right off of the PPU, and the picture is wobbly. And you might be tempted to say, now wait a second Nicole, this is composite video. You wrote a whole post on it! Composite video is inferior to other signals because it’s basically a form of video signal compression. And that’s true; but there’s no reason a composite frame should differ from frame to frame, is there? Here’s my beautiful Apple ][ running Shanghai (as referenced in a recent post ). You don't have a video tag support or something? So you can't see this footage of the *Shanghai* title screen? Ah too bad. That’s incredibly static! Explanation Attempt 1: Interference Interference isn’t actually as big of a problem as you’d expect. It’s probably something you’re thinking about, but interference would generally present as a random pattern, not the cyclic noise seen on the NES screenshot. In fact, the Apple video was captured using a much longer cable, being strewn over my desk where several electronics were running, and you can actually see some noise in the white parts of the image. But it’s noise; it’s uncorrelated to the input signal. This is the letter “B” from Mighty Bomb Jack above, crapped from the raw capture. Notice the repeating jagged pattern on the left side of the letter “B” where the white meets the blue of the sky. If this was just signal interference from outside, there’d be no reason to expect it to follow the images that closely. Explanation Attempt 2: The colorburst If we divide the colorburst frequency of ~3.57 MHz by the NTSC linerate of 15.734kHz, we get a near-exact 227.5. That’s no coincidence; RCA deliberately aimed to have the color carrier a half-integer multiple of the linerate. That’s because if one scanline is similar to the next line, it’ll be a signal with a frequency similar to the linerate. It’s very rare, on the other hand, for the television signal to have components that are a half-integer multiple; so this makes it easier to filter out the color signal. I talked about this a bit in my 2021 post. You might notice something here. The colorburst is expected to just be a portion of a continuous 3.57 MHz signal. That’s signal do