Glad I could help! 😀

Yeah... I agree. Some seriously smart people designed this stuff!

@@JohnsBasement All with nary a DSP block - or transistor - in sight 🙂

Thanks for saying!

A prior employer threw one out. It was on its last leg. I looked at it and thought "should I?" Never thought I'd need it. Till now. 🙄

yup, it'was called "color framing" and an annoying problem editing with direct NTSC color record broadcast VTRs. Often the edit point was a frame off from where you wanted it to maintain the color field sequence. If ignored there was a 140ns H shift in the image at the edit. But if the edit was not a match frame, the production industry often did a non color framed edit anyway as with a scene change, you would not notice the H shift. And then there was 3/2 pulldown from film sources - that's another story. Note that PAL had an eight field sequence!

Thanks. I'll try not to let ya down!

It changes in NTSC. I misspoke when discussing WHEN the NTSC color burst changes. It is supposed to shift 180 degrees each FRAME. Not on each FIELD.

PAL stands for "People Are Lavender", due to the inaccurate color reproduction.

@@activelow9297 🤣

@@JohnsBasement Lol, you first heard that one now, in 2023? I got another one for you.. CP/M stands for "conspiracy to preserve the ministry".. because evidently Gary Kildall admired the arcane and eldritch OSes and job control languages of 60's mainframes and wanted to cultivate a similar priesthood of experts in the microcomputer world. I heard that one back in the 80's.

The French SECAM was "system essentially contrary to American methods", and another one for PAL - "peace at last".

The people that came up with these things and got them all working with the commodity technology they had at the time are geniuses! These days, I get to make pretty pictures with VGA and ONLY have to care about the hsync & vsync! (yeah... I know I am ignoring gamma correction. It'll look good enough for a terminal screen and some video games!)

Glad you liked it

I look at NTSC today and can't believe how bad it looks after 20 years of 1080p. How did we EVER survive??? :-D

Thanks!

The color burst? It is both amplitude and phase modulated. You want to ask this on the Z80Retro discord channel. There are some very good experts on this subject that lurk in there!

What do you mean by "fit?" There's just one thing changing here -- the voltage level over time. So at 54mV you see black, at 1.0V you see white. You only see color when you "wiggle" that voltage close to 3.58 million times per second. It's just one continuous signal as you stripe across the screen, and sometimes it wiggles (color) and sometimes it doesn't (pure black or white). "Pixels" aren't a real concept in analog video (a pixel is a digital concept -- I arrange a buffer of colors I want in a 2d array of pixels for example). The *effective* rate that you can change your voltage level on an analog signal is what loosely corresponds to a pixel. In other words, if you have a really slow, kind of ineffective video device (like say the Atari 2600), it can't change that signal as fast as the TV is able to, and so it's "pixels" are constrained by the speed at which it can generate a scanline with a given color wiggle, and thus those old devices looked "blocky" when they produced video. If you're wondering what the highest *theoretical* speed at which you could change that signal, he explained that in the video -- it's somewhere in the 300 - 650 times per scanline range (it varies because different tvs will act differently -- some old vacuum tube driven TV probably can't do better than 300 changes per scan line, but a brand new circa 1990 tube tv with lots of digital components might be able to show 650 changes per scan line). Above that 300 - 650 changes per line, your TV's analog circuitry won't be able to keep up, and it will smear them in some way (producing incorrect colors, or simply not displaying an individual change you had in your voltage stream).

How many 3.8MHZ time periods can fit into one active display scan line? Once you exceed changing the luma at that rate, it is likely that a TV can't differentiate between interpreting it as a color and as a brightness.

@@Calphool222 What I am trying to understand is how that 'wiggle' ( I assume a sine wave) determines the color. I get it has to do with the phase of that 'wiggle' but lets say I wanted to use a micro controller, like a Pi Pico to generate this signal, and I want to get at least 8 bit color up on the screen, I need to wiggle that signal at a phase difference from the color burst? I get that the color burst is telling the TV that a color signal is incoming so is that color burst frequency for each 'pixel' color just a phase difference from the original color burst? I do understand that with a micro controller you wont be generating a sine wave but a square wave which I imagine should work, no?

@@JohnsBasement Well... say you had a signal capable of 8 bit color, 300 or more 'pixels' on a single 15.7khz ...and lets round that 'pixel' count to a standard like 320, you will need to modulate that color burst at the correct phase for each 'pixel' at around 49.2(rounded up) times per scan line if my math is correct. So I am guessing that 'wiggle' per 'pixel' would have to fit in at the proper phase for each color 'pixel' within that 1/49th for each 'pixel'?

@@GORF_EMPIRE You kind of have to understand a little bit about AC signals to grasp what "phase difference means." Imagine any AC waveform. If you say it is at 0 degrees, that means it starts at position 0 and swings up and down at whatever its frequency is. If you say it is at 90 degrees, then it will start part way through a swing (not at 0). When you compare that waveform to another waveform at the same frequency, they either overlap (their phases are the same) or one precedes the other. You can *measure* how much one precedes the other, and get a "phase difference." Now, imagine a color wheel. In the center is gray, and all around the outside are all the colors of the rainbow. The gray bleeds into the colors. They are most radiant at the outside and most gray in the center. Any color in the NTSC scan line signal can be represented as a point in this color wheel. The *phase difference* tells you the angle on the color wheel, and the *amplitude* tells you how far out toward the outside edge (where the color is most vibrant) of the color wheel to go.

@@katarsisAX 😂

Yep. And it looks pretty decent for the camera technology of the time. It is unfortunate that crisp vertical edges are so troublesome.

😂

Sorry. That is not my thing.