Demystifying NTSC Color And Progressive Scan

NTSC

Black and white NTSC is simple – it can, and was, done with vacuum tubes for a long, long time. Color is just weird, though. It runs at 29.976 frames per second, uses different phases of the carrier for different colors, and generally takes a while to wrap your head around. [Sagar] is doing a series on the intricacies of NTSC, and the latest post deals with color and progressive scanning versus interlacing, or as it is better known, how classic game consoles and home computers generate video.

The test bed for [Sagar]‘s video experimentations is a circuit containing an ATMega16, a 4-bit shift register, and a 14.31818 MHz clock. This clock is much faster than the 3.579545 MHz clock in an NTSC carrier frequency – exactly four times as fast – allowing the shift register to output four different phases of the carrier frequency a 0°, 90°. 180°, and 270°. Playing with some of the pins on the ATMega in the circuit results in a palette being generated on any old TV.

NTSC requires interlaced scanning, or sending an entire screen of even lines, then an entire screen of odd lines, at around 60 fields per second. The Nintendos and Segas of yesteryear didn’t bother with this, instead opting to send half the vertical resolution at double the frame rate. This is known as a progressive scan. [Sagar] found that this resulted in some image artifacts when displayed on a modern LCD, and moving back to an interlaced mode fixed the problem. All the code and files are up on the gits. If you’re feeling adventurous, this is exactly how projects like the Uzebox have created homebrew game consoles using little more than the ATMega found in [Sagar]‘s build.

The Open Hardware Driver For CRTs

driverCRTs are the king of displays for any homebrew project. They have everything – high voltages, high vacuums, X-rays, and the potential for a vector display – that makes a project exude cool. Getting an old CRT up and running, though, that’s another story. Never rear, because now there’s an Open Hardware eletrostatic CRT driver for your next display.

[Eric] designed a driver circuit that should be able to send a picture to most 2″, 3″ and some 5″ electrostatic CRTs, the kind found in ancient TVs and oscilloscopes. The 1kV power supply uses a transformer usually found in a CCFL bulb, and is able to produce several milliamps. You’ll want to keep one hand behind your back when working on this.

The driver circuit takes a 0-3.3V analog signal for deflecting the beam along the X and Y axis. The amplifier has enough bandwidth to handle NTSC video, so displaying video along with vector letters and shapes is also a possibility with this circuit. Most of the files are available on the git, with three boards available to be ordered from OSHPark.
Thanks [Mike] for the tip.

The Hovering, Holographic, Star Wars Display

Tweetergif

While we’re still a long way off from the Star Wars telepresence holographic displays, this build over on the Projects site is the closest we’ve seen yet. Even better, it can be built in a garage for not much money.

Inside the Hoverlay are a few fans and a pair of ultrasonic atomizers that turn water into an extremely fine mist. The fans pull this vapor up through the base of the display and through simple drinking straws to create a laminar sheet of water vapor. Put a projector behind this thin sheet of vapor, and you have a display, seemingly floating in mid-air.

The base of the display can be scaled up, simply by putting several units together in a line. It’s still just a prototype – future versions will improve the stability and reduce the thickness of the fog layer – but it’s still a very cool build for a custom holographic display.

[Read more...]

Vector Graphic Flappy Bird Harder Than It Should Be

 

The dark room at Maker Faire was loud,  after all it’s where Arc Attack was set up plus several other displays that had music. But if you braved the audio, and managed not to experience a seizure or migraine from all the blinking you were greeted with these sharply glowing vector displays on exhibit at the TubeTime booth. We did the best we could with the camera work, but the sharpness of the lines, and contrast of the phosphorescent images against the black screen still seems to pop more if viewed in person.

This isn’t [Eric's] first attempt at driving high-voltage tube displays. We previously covered his dekatron kitchen timer. But we’d say he certainly stepped things up several notches in the years between then and now. He blogged about Asteroids, which is running on the same hardware as the Flappy Bird demo from our video above. An STM32F4 Discovery board is running a 6502 emulator to push the game to [Eric's] CRT vector driver hardware.

Just before we were done at the booth, [Eric] turned to us with a twinkle in his eye. He confessed his delight in purposely leaving out any button debounce from the Flappy Bird demo. As if it wasn’t hard enough it tends to glitch after passing just a few of the pipe gates. Muhuhahaha!

Neo Geo Gets Line Doubled

NeoGeoScan

We love old video games, but we hate the way analog interlaced video looks on our new LCD monitors. [Michael] feels the same way, so he’s created NeoVGA, A Neo Geo Line Doubler in VHDL. Neo Geo, like many classic consoles, didn’t use the full resolution of an analog TV. In NTSC mode, it ran at 320×224 pixels. PAL users got an extra 32 vertical pixels for 320×256 pixels. The system ran with an approximately 15kHz horizontal sync and ~60Hz vertical sync.

This is not exactly a VGA compatible signal, so it would be relegated to composite or S-Video capable displays. The signals looked pretty good on a CRT, but on an LCD, they tend to look crummy. Modern LCDs don’t natively handle interlaced and/or low resolution input signals. The TV’s controller performs the magic of buffering, interpolating, and transforming the input signal to be compatible with the LCD panel. As [Michael] explains, most of these algorithms are optimized for TV video signals with lots of motion. They perform poorly on static high contrast images such as the background of a fighting game. TV controllers also add lag to the signal chain. Not much of a problem when watching movies, but it’s a big problem when you’re trying to pull off that triple hit combo.

Click past the break for more on [Michael's] creation.

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Hacking An Old Parallel Port Webcam To Work With A Gameduino 2

connecting parallel port web camera to gameduino 2

[Andrew] couldn’t pass up a 20ish year old parallel port based webcam he saw on the shelf at a thrift store. It’s a Connectix QuickCam and was the first webcam that did not require a separate video input card to interface with your computer. Due to this feature, the webcam was extremely popular, so popular that Logitech ended up buying Connectix and marketing the camera for themselves.

It’s tough to find a newer computer that still has a parallel port, but using an old computer wasn’t [Andrew]‘s plan anyways. After thinking about it, he decided to try to get the camera’s image to display on a Gameduino 2.

The hardware list is fairly minimal. The cam’s parallel connector is plugged straight into STM32 Nucleo development board by way of several jumpers. The Gameduino 2 is connected to the dev board and a USB to PS/2 adapter was made to power the camera.

[Read more...]

1980’s Ingenuity Yields Mechanical Intervalometer

DIY Intervalometer

Let’s go back in time to the 1980’s, when shoulder pads were in vogue and the flux capacitor was first invented. New apartment housing was being built in [Vince's] neighborhood, and he wanted some time-lapse footage of the construction. He had recently inherited an Elmo Super-8mm film camera that featured a remote control port and a speed selector. [Vince] figured he might be able to build his own intervalometer get some time-lapse footage of the construction. He was right.

An intervalometer is a device which counts intervals of time. These are commonly used in photography for taking time-lapse photos. You can configure the intervalometer to take a photo every few seconds, minutes, hours, etc. This photographic technique is great when you want see changes in a process that would normally be very subtle to the human eye. In this case, construction.

[Vince] started out by building his own remote control switch for the camera. A simple paddle-style momentary micro switch worked perfectly. After configuring the camera speed setting to “1”, he found that by pressing the remote button he could capture one single frame. Now all he needed was a way to press the button automatically every so often.

Being mechanically minded, [Vince] opted to build a mechanical solution rather than an electronic circuit. He first purchased a grandfather clock mechanism that had the biggest motor he could find. He then purchased a flange that allowed him to mount a custom-made wooden disk to the end of the minute hand’s axle. This resulted in a wheel that would spin exactly once per hour.

He then screwed 15 wood screws around the edge of the wheel, placed exactly 24 degrees apart. The custom paddle switch and motor assembly were mounted to each other in such a way that the wood screws would press the micro switch as they went by. The end result was a device that would automatically press the micro switch 15 times per hour. [Read more...]