8 ms·

Al Alcorn, creator of Pong, explains the NTSC color graphics trick

89 points by mpweiher 7y ago

masonic 7y ago
NTSC, not NSTC.
- dylan604 7y ago
  Exactly. Never The Same Color
  - rbanffy 7y ago
    Or "Never Twice The Same Color"
    - anticensor 7y ago
      National Television System by Committee* *Committee stands for National Television System Committee
      - dylan604 7y ago
        Are you trying to say that it is a recursive name like GNU?
        anticensor 7y ago
        NTSC as the name of the committee is not, NTSC as the name of the system is.
  - duskwuff 7y ago
    The US digital television standard is called "ATSC". Officially, this stands for "Advanced Television Systems Committee". Unofficially, the "A" stands for "always".
    - joezydeco 7y ago
      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-Government-Revolution/dp/0156005972 https://www.amazon.com/Defining-Vision-Broadcasters-Governme... 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.
- szczys 7y ago
  Well also not really NTSC either. Did you see the part where he talks about them trying to get a recording of gameplay for the commercial? > "We can't get it to play on the videotape recorder, why?” I say, "Well, it's not really video! There’s no interlace… Treat it as though it’s PAL, just run up through a standard converter.”
blakesterz 7y ago
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.
- pjc50 7y ago
  Really highlights the workings of "Baumol cost disease" in general: TVs themselves have got cheaper, so everyone can have one for a fraction of their income. The relative cost of repair labour has gone up, as well as the devices getting less repairable, so TV repairmen are no longer a major source of employment. While college - which entirely consists of paying for the skilled labour of others, as well as buildings - has gone up hugely by comparison. Someone should calculate the historical cost of college in terms of how many televisions you could have bought instead.
  - dkdk8283 7y ago
    Not limited to TVs. Appliance repair in general has been replaced with disposable appliances. Human rights violations in countries like China is to blame for reducing the value of skilled labor.
    - mikepurvis 7y ago
      It's true, and a huge shame, particularly as it's driven appliances to be made with parts not designed to last beyond a 10 year lifespan. That said, it's been interesting to witness the recent rise in YouTube repair guides coupled with online parts stores. Obviously not for everyone, but I've had good results repairing two different washing machines, a stove, a coffee grinder, my hot tub, a laptop, a video game controller, etc. For a lot of those I would have felt completely overwhelmed and not known where to start without a video tutorial.
  - rbanffy 7y ago
    The TV set index seems like a nice counterpart to the Big Mac Index.
skibz 7y ago
"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 7y ago
  We really could stand to come back to those days of collaboration, freedom, and hands on practical development.
- drudru11 7y ago
  Totally. I really like that he has kept it all these years.
jefftk 7y ago
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 7y ago
  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.
pavlov 7y ago
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-illustrated/ https://int10h.org/blog/2015/04/cga-in-1024-colors-new-mode-...
- PunksATawnyFill 7y ago
  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.
kragen 7y ago
> 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.
drudru11 7y ago
This is a really good story. It is important to remember that this is the spirit that built Silicon Valley.
peter_d_sherman 7y ago
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."

89 points by mpweiher 7y ago

masonic 7y ago

NTSC, not NSTC.

dylan604 7y ago
Exactly. Never The Same Color
- rbanffy 7y ago
  Or "Never Twice The Same Color"
  - anticensor 7y ago
    National Television System by Committee* *Committee stands for National Television System Committee
    - dylan604 7y ago
      Are you trying to say that it is a recursive name like GNU?
      - anticensor 7y ago
        NTSC as the name of the committee is not, NTSC as the name of the system is.
- duskwuff 7y ago
  The US digital television standard is called "ATSC". Officially, this stands for "Advanced Television Systems Committee". Unofficially, the "A" stands for "always".
  - joezydeco 7y ago
    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-Government-Revolution/dp/0156005972 https://www.amazon.com/Defining-Vision-Broadcasters-Governme... 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.
szczys 7y ago
Well also not really NTSC either. Did you see the part where he talks about them trying to get a recording of gameplay for the commercial? > "We can't get it to play on the videotape recorder, why?” I say, "Well, it's not really video! There’s no interlace… Treat it as though it’s PAL, just run up through a standard converter.”

blakesterz 7y ago

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.

pjc50 7y ago
Really highlights the workings of "Baumol cost disease" in general: TVs themselves have got cheaper, so everyone can have one for a fraction of their income. The relative cost of repair labour has gone up, as well as the devices getting less repairable, so TV repairmen are no longer a major source of employment. While college - which entirely consists of paying for the skilled labour of others, as well as buildings - has gone up hugely by comparison. Someone should calculate the historical cost of college in terms of how many televisions you could have bought instead.
- dkdk8283 7y ago
  Not limited to TVs. Appliance repair in general has been replaced with disposable appliances. Human rights violations in countries like China is to blame for reducing the value of skilled labor.
  - mikepurvis 7y ago
    It's true, and a huge shame, particularly as it's driven appliances to be made with parts not designed to last beyond a 10 year lifespan. That said, it's been interesting to witness the recent rise in YouTube repair guides coupled with online parts stores. Obviously not for everyone, but I've had good results repairing two different washing machines, a stove, a coffee grinder, my hot tub, a laptop, a video game controller, etc. For a lot of those I would have felt completely overwhelmed and not known where to start without a video tutorial.
- rbanffy 7y ago
  The TV set index seems like a nice counterpart to the Big Mac Index.

skibz 7y ago

"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 7y ago
We really could stand to come back to those days of collaboration, freedom, and hands on practical development.
drudru11 7y ago
Totally. I really like that he has kept it all these years.

jefftk 7y ago

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 7y ago
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.

pavlov 7y ago

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

PunksATawnyFill 7y ago
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.

kragen 7y ago

> 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.

drudru11 7y ago

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

peter_d_sherman 7y ago

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."