I tried looking it up myself, because it sounds interesting, but of course search results are polluted with articles on vantablack. "Super black TV" and related search terms just bring up garbage about OLED TVs and such.
Doing this allowed "true 0V" (i.e. gaps cut out of the modulated signal by electronic post-processing, below the "minimum" intensity of 1V, where you're just getting carrier) to act as a form of in-band signalling. 0V was used "outside" the image to both synchronize the TV's raster electronics, and inform said electronics of the period of time they should be off altogether, rather than firing even a weak electron beam. (This most noticably prevents your CRT from drawing a subtle diagonal swoosh when it starts each new frame.)
See also: the terms "front porch" and "back porch" (in e.g. https://electronics.stackexchange.com/questions/201011/what-...), referring to the parts of each scanline that are 0V.
Just showing raw static was much more common though.
Because the color signal is optional, TV receivers had to have a detector for it to enable color. Noise didn't contain the "color burst" that identified the color signal, so noise showed as black and white noise, not colored confetti. At least until TV receivers acquired enough signal processing that no-signal produced a "No Signal" message, a blue screen, or a channel guide.
Gibson has written that he has mixed feelings about that line. Great line, but dates the work.
Frequently these TV's would have a "muting" mechanism - if you selected a channel without a signal, it would mute the audio and display a blue background instead of the underlying signal.
When LCD TV's and HDTV started gaining traction the "No Signal" screen was often some text bouncing around in some manner.
Like snow, even. Hence 'Snow Crash'. :)
I imagine the sky in a predominantly cold, snowy or rainy place could look a bit like static. Dry sunny climates are tend to be more "A/V 1" blue. :)
shhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhh
Sandin also had a distribution philosophy that was a precursor (early contemporary?) to FOSS: he called it “copy-it-right”. He’d send anyone a copy of the schematics, but you were expected to build it as designed and not get creative until you at least had it working properly. The process of building the machine was also supposed to teach you how it worked.
Many moons ago I emailed Sandin and got a copy of the plans. They’re a hell of a document. Unfortunately some critical components are no longer in production, and updating the schematics was beyond my skill (setting aside that the scale and expense of the project was also beyond me, but hey).
Superblack: A value on the wave form monitor of 0 or less luminance units. 7.5 units is standard TV black. Graphics and logos placed on superblack are much easier to work with.
You will see that the area around the logo is glowing slightly, and that the area opposite the logo is completely lights out.
That is, essentially, the difference between "black" and "superblack". Both areas are displaying black, but one area is backlit and the other is not. Lit black is clearly different from Unlit black, because LCD pixels aren't perfectly opaque.
If you have an OLED TV (or an OLED phone, like a top-end iPhones), then every black pixel is superblack, which is why it looks so high contrast and gorgeous. If you have an LCD phone, you can see the "lit black" thing — but probably only if you set it next to an OLED phone.
Folks who know what "235" has to do with this, yes, I know, but I'm only addressing "what that might actually look like", not "deep dive into the RGB low/high problem". Feel free :)
I'm not a TV engineer, I was a journalist, so here's what I remember:
Superblack was a special kind of black. When you watched analog TV and the video faded to black, the screen was black. But that was a transmission black. It wasn't as black as was electrically possible. There was always still some signal there generating not-quite-black.
The not-quite-black was largely an artifact of video tape, and all the dozens of machines a video signal had to go through from playback to broadcast. If you were watching black recorded on tape, it was never quite black. An ordinary person would never notice that it wasn't perfectly black, but you could see it if you were in a TV station with oscilloscopes monitoring the signal at various points in the video chain. IIRC, it was like -1db, or something like that.
You could see it at home, if you tried. If you knew what to look for. The easiest way to do it was to turn the brightness up on your TV and look for the dark dark dark grey at the beginning and the end of commercial breaks. That wasn't superblack, that was regular black. But superblack would be next.
In a videotape room or an editing suite, you could see superblack quite easily. Watching a tape with black on it on an analog monitor showed regular black. When you ejected the tape, the monitor would go a shade darker: superblack. The blackest the monitor could electrically be without actually being off.
Superblack could be used for all kinds of things. I only remember three off the top of my head.
First, primitive chroma-key effects in the days before digital video. It wasn't great, and you'd need extra equipment down the line to boost the signal because it would get dark, and then boosting the signal made it look bad, so it was rarely used.
Second, the equivalent of today's alpha channel compositing. This was more common, but still resulted in some signal degradation. But it was how you could put chyron or an OTS over video or a live signal.
Third, was the TV station equivalent of a "silence sense." When I worked in radio, each station had a gadget called a "silence sense" that would be hooked up to an ordinary radio tuned to the station. If there was silence for longer than x number of seconds, it tripped a relay that flipped on red blinking light bulbs in the DJ booth, in the newsroom, in the PD's office, in the MD's office, and if you were unlucky, the GM's office. In non-studio locations it was often accompanied by a beeping noise. The idea was to let everybody in the building know that something had gone horribly wrong and there was nothing on the air. Some stations I worked at it was set for 10 seconds. Some as few as 3. Really, it depended on the type of music the station played.
A similar gadget could be made (most of these things were home-made by the station engineer) to look for superblack in a TV signal. Too much superblack, and alarms go off everywhere.
Fourth, Panasonic is the only company I know of that used superblack in the consumer arena. It made a VCR that, after a show was recorded, would automatically rewind and re-watch the show for you. When it sensed superblack, it would mark the location on the tape. Then when a person went to watch what was recorded later, the VCR could sense the marks it made previously and use them to fast forward through the commercials in the program. This worked because there would always be superblack inadvertently broadcast at the start and at the end of each commercial set where there was a break in the video chain from the switch between the show playback machine and the commercial break's playback machines. I had one of these machines. It worked really well, except that it made all kinds of chugging and whirring noises in the night while it marked the tape.
Again, I'm not an engineer, so I'm just working from memory. But I'm typing what I know here because so much information about these sorts of things has disappeared, and the people who know more about these things are mostly dead.
I assume that videos used the same machinery, possibly in software, so that you couldn't take screenshots for copyright reasons. Or maybe it was faster for some reason, who knows (Raymond Chen might).
Either way, it's probably unrelated.
But this is indeed tangential and not relevant to the original comment, because the chroma key color could be anything. On one particular driver I had, I remember the chroma key color was a very ugly shade of brown :)