
Al Alcorn, creator of Pong, explains the NTSC color graphics trick - mpweiher
https://spectrum.ieee.org/tech-talk/tech-history/silicon-revolution/al-alcorn-creator-of-pong-explains-how-early-home-computers-owe-their-color-to-this-one-cheap-sleazy-trick
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skibz
"When the Apple II was being done, I helped them. I mean, I actually loaned
them my oscilloscope, I had a 465 Tektronix scope, which I still have, and
they designed the Apple II with it. I designed Pong with it."

Damn, that scope is a serious piece of history.

~~~
triptych
We really could stand to come back to those days of collaboration, freedom,
and hands on practical development.

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jefftk
_AA: In one repair shop, there was a real cheap, sleazy color bar generator
[for testing televisions]. And instead of doing color properly by synthesizing
the phases and stuff like that, it simply used a crystal that was 3.58
megahertz [the carrier frequency for the color signal] minus 15.750 kilohertz,
which was the horizontal scan frequency. So it slipped one phase, 360 degrees,
every scan line. You put that signal on the screen and you’ve got a color bar
from left to right. It really was really the cheapest, sleaziest way of doing
it!_

 _AA: Anyway, part of the way into the design, Nolan said, “Oh, by the way, it
has to be colored.” But I knew he was going to pull this stunt, so I’d already
chosen the crystal [that drove the chip] to be 3.58 MHz, minus 15.750
kilohertz._

 _SC: So, in the home version of Pong, the graphics would simply change color
from one side of the screen to the other?_

 _AA: Right, the whole goal for doing this was just to put on the box:
“Color!”_

I'd never seen Pong in color, but having a simple color gradient across the
screen works very well for the game. You can see the ball changing color as it
crosses the screen, which is a bit weird, but nothing else looks out of place:
[https://www.youtube.com/watch?v=F73cgR63Jn4](https://www.youtube.com/watch?v=F73cgR63Jn4)

~~~
dylan604
If you look at the video signal on a waveform and zoom in on the front porch
area of the signal, you can see the color burst. It looks like a group of 9 (i
think) spikes. The first spike is supposed to go up, but it was possible to
have the color burst "flipped" so that the first spike went down. (Maybe I
have it backwards, been a looong time.) If that happened during a broadcast,
the FCC would issue fines. There was a very expensive piece of video equipment
that was meant for doing video effects during post production (3DO maybe?). If
you had a flipped burst, you could pass your signal through it without using
any of the effects, and it would get corrected. For a time, the post house I
worked at said they made more money using it for that purpose than what it was
designed to do. That was all before my time though. Supposedly, some poor
engineer would have to watch all incoming video tapes with the waveform zoomed
in to the color burst just to watch for these flips. If it occurred, they
would reject the tape.

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pavlov
This article contains a visual explanation of NTSC color artifacting, and how
it can be used to get 1024 colors out of IBM's 1981 original PC CGA:

[https://int10h.org/blog/2015/04/cga-in-1024-colors-new-
mode-...](https://int10h.org/blog/2015/04/cga-in-1024-colors-new-mode-
illustrated/)

~~~
PunksATawnyFill
I remember this being used in games on the Atari computers, but only those
that were ports of Apple games and Apple’s crude graphics. By skipping
horizontal pixels, they’d get composite NTSC to smear the area into a color.

But the Ataris had S-video outputs (in 1978!), which of course is not
composite. The color resolution is too high to produce artifacts when using
separated video, so those games were essentially black & white on a good
monitor like the Commodore 1702 hooked up with separated Y & C signals.

The Ataris were great, forward-thinking computers.

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peter_d_sherman
Excerpts:

"Analog NTSC televisions generate color by looking at the phase of a signal
relative to a reference frequency."

[...]

"And instead of doing color properly by synthesizing the phases and stuff like
that, it simply used a crystal that was 3.58 megahertz [the carrier frequency
for the color signal] minus 15.750 kilohertz, which was the horizontal scan
frequency. So it slipped one phase, 360 degrees, every scan line. You put that
signal on the screen and you’ve got a color bar from left to right."

------
drudru11
This is a really good story. It is important to remember that this is the
spirit that built Silicon Valley.

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blakesterz
Not exactly related to the topic at hand, but that opening paragraph really
caught my eye:

"I had my father sign me up for an RCA correspondence course on radio and
television repair. So, by the time I got to Berkeley, I was a journeyman TV
repairman and actually paid my way through college through television."

Sometimes it's had to believe just how much the cost of college has changed
since the 60s/70s.

~~~
JoeAltmaier
I started college in 1976. $300 per semester, 16 hours. Textbooks cost around
$100 (all of them together).

But I earned $2.75/hr at the college computer lab as a lab monitor. So yeah.

~~~
logfromblammo
So tuition and texts could be paid with 150 hours of on-campus labor. Let's
call that 15% part-time. Someone on 20 hour/week 50% part-time would therefore
have wages left over for things like food, clothing, and housing, and time
left over for actually being a student.

Now, tuition and text can only be paid with 100% or less of a full-time wage
job if you are an in-state student at a public university, or attend a
community college. And then, no time or money left over for lectures, study,
or basic survival.

In terms of student labor hours per semester, college tuition and textbooks
have increased an average of 4%-5% per year from JoeAltmaier's 1976 numbers to
2020. Due to advances in efficiency, infrastructure, and technology, that
metric should be _decreasing_ every year for most goods. Some see large
downward jumps as machines are invented that allow one person to do jobs that
formerly required more laborers.

What the hell have universities been doing? Do they not all have economics
departments and business schools?

~~~
michaelbrave
Costs have gone up mostly because of decreases in government funding toward
college.

~~~
JoeAltmaier
Oh yea. Our 'state college' gets only 5% of its operating funds from the
state. I don't know why they don't just go private.

------
masonic
NTSC, not NSTC.

~~~
dylan604
Exactly. Never The Same Color

~~~
duskwuff
The US digital television standard is called "ATSC".

Officially, this stands for "Advanced Television Systems Committee".

Unofficially, the "A" stands for "always".

~~~
joezydeco
If you're an insomniac, I recommend David Brinkley's book "Defining Vision :
How Broadcasters Lured the Government into Inciting a Revolution in
Television"

It's an account of the incredibly messy process that got us the ATSC standard
in the USA. A little dry but a little interesting.

[https://www.amazon.com/Defining-Vision-Broadcasters-
Governme...](https://www.amazon.com/Defining-Vision-Broadcasters-Government-
Revolution/dp/0156005972)

The upside is that the group took so long to define a standard that digital
compression and broadcasting technologies matured enough so that HDTV in the
US could be fully digital and not analog like the Japanese had pioneered and
proposed as a world standard.

------
kragen
> _In those days, in Silicon Valley, we didn’t keep secrets._

That's how Silicon Valley was created from the 1950s through the 1980s, and
still to a significant extent through the 1990s: knowledge was not treated as
property, but rather as a commons. This is the foundation of the professions:
judges and lawyers do not keep their reasoning secret, nor do priests, nor do
professors, nor do medical doctors — to the extent that the knowledge they
create belongs to anyone, it belongs to the profession, not to the individual
professional or their client. When Silicon Valley started abandoning that
principle in the 1990s and especially after 2000, the epicenter of innovation
shifted to Shenzhen, where that principle was still practiced. And today with
the covid pandemic we see the fallout: the US has been left far behind
technologically and is completely unable to deploy the measures needed to stop
the pandemic.

That isn't the only factor, of course, but it's a big one. The profession of
engineering computing machinery has been subordinated to the quarterly goals
of business, which can be more effectively promoted if information flow is
controlled by management and money, not by engineers and sharing. But the
innovation that remains vital in Silicon Valley today is underpinned by open-
source software, which is based on the same kind of promiscuous openness that
got Steve Wozniak debugging Atari machines for free on the late shift. Too bad
free software can't tell if you've got a fever.

