Never Twice the Same Color: Why NTSC is so Weird

Ever wonder why analog TV in North America is so weird from a technical standpoint? [standupmaths] did, so he did a little poking into the history of the universally hated NTSC standard for color television and the result is not only an explanation for how American TV standards came to be, but also a lesson in how engineers sometimes have to make inelegant design compromises.

Before we get into a huge NTSC versus PAL fracas in the comments, as a resident of the US we’ll stipulate that our analog color television standards were lousy. But as [standupmaths] explores in some depth, there’s a method to the madness. His chief gripe centers around the National Television System Committee’s decision to use a frame rate of 29.97 fps rather than the more sensible (for the 60 Hz AC power grid) 30 fps. We’ll leave the details to the video below, but suffice it to say that like many design decisions, this one had to do with keeping multiple constituencies happy. Or at least equally miserable. In the end [standupmaths] makes it easy to see why the least worst decision was to derate the refresh speed slightly from 30 fps.

Given the constraints they were working with, that fact that NTSC works as well as it does is pretty impressive, and quite an epic hack. And apparently inspiring, too; we’ve seen quite a few analog TV posts here lately, like using an SDR to transit PAL signals or NTSC from a microcontroller.

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Hand Gestures Play Tetris

There are reports of a Tetris movie with a sizable budget, and with it come a plentiful amount of questions about how that would work. Who would the characters be? What kind of lines would there be to clear? Whatever the answers, we can all still play the classic game in the meantime. And, thanks to some of the engineering students at Cornell, we could play it without using a controller.

This hack comes from [Bruce Land]’s FPGA design course. The group’s game uses a video camera which outputs a standard NTSC signal and also does some filtering to detect the user. From there, the user can move their hands to different regions of the screen, which controls the movement of the Tetris pieces. This information is sent across GPIO to another FPGA which uses that to then play the game.

This game is done entirely in hardware, making it rather unique. All game dynamics including block generation, movement, and boundary conditions are set in hardware and all of the skin recognition is done in hardware as well. Be sure to check out the video of the students playing the game, and if you’re really into hand gesture-driven fun, you aren’t just limited to Tetris, you can also drive a car.

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Color TV Broadcasts are ESP8266’s Newest Trick

The ESP8266 is well known as an incredibly small and cheap WiFi module. But the silicon behind that functionality is very powerful, far beyond its intended purpose. I’ve been hacking different uses for the board and my most recent adventure involves generating color video from the chip. This generated video may be wired to your TV, or you can broadcast it over the air!

I’ve been tinkering with NTSC, the North American video standard that has fairly recently been superseded by digital standards like ATSC. Originally I explored pumping out NTSC with AVRs, which lead to an entire let’s learn, let’s code series. But for a while, this was on the back-burner, until I decided to see how fast I could run the ESP8266’s I2S bus (a glorified shift register) and the answer was 80 MHz. This is much faster than I expected. Faster than the 1.41 MHz used for audio (its intended purpose), 2.35 MHz used for controlling WS2812B LEDs or 4 MHz used to hopefully operate a reprap. It occasionally glitches at 80 MHz, however, it still works surprisingly well!

The coolest part of using the chip’s I2S bus is the versatile DMA engine connected to it. Data blocks can be chained together to seamlessly shift the data out, and interrupts can be generated upon a block’s completion to fill it in with new data. This allows the creation of a software defined bitstream in an interrupt.

Why NTSC? If I lived in Europe, it would have been PAL. The question you’re probably thinking is: “Why a dead standard?” And there’s really three reasons.

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Retro Games on ArduinoCade Just Shouldn’t Be Possible

Making retro video games on today’s micro controllers brings many challenges, especially when using only the micro controller itself to handle the entire experience. Complex graphics, sound, game logic and input is taxing enough on the small chips, toss in NTSC color graphics and you have a whole different bear on your hands.

[rossum] set out making the Arduinocade retro game system using an overclocked Arduino Uno, and not much more. Supporting 4 voice sound and IR game controllers, the system also boasts 27 simultaneous colors all in software. These colors and the resolution feel like they’re impossible without a graphics chip to offload some of the work. While doing all of this the ATmega328p is also playing some faithful reproductions of classic arcade games.

The uses a couple of interesting tricks. Color is generated with NTSC color artifacts, where the screen is really black and white, but thanks to a delay or two in the signal generation the bits are out of phase from the reference “color burst” signal and appear on-screen as unique colors. This approach was used in the 8 bit Apple II personal computers to generate its colors, and also on the early IBM PC’s with CGA cards to drastically increase color depth. In this case, the chip is overclocked with a 28.6363 MHz crystal (a multiple of NTSC timing) and the SPI hardware leveraged to shift out all the necessary pixels. Check out how great it looks and sounds after the break.

It’s good to see an old trick on a new project and we are off to play some games!

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FPGAs Keep Track of your Ping Pong Game

It’s graduation time, and you know what that means! Another great round of senior design projects doing things that are usually pretty unique. [Bruce Land] sent in a great one from Cornell where the students have been working on a project that uses FPGAs and a few video cameras to keep score of a ping-pong game.

The system works by processing a live NTSC feed of a ping pong game. The ball is painted a particular color to aid in detection, and the FPGAs that process the video can keep track of where the net is, how many times the ball bounces, and if the ball has been hit by a player. With all of this information, the system can keep track of the score of the game, which is displayed on a monitor near the table. Now, the players are free to concentrate on their game and don’t have to worry about keeping score!

This is a pretty impressive demonstration of FPGAs and video processing that has applications beyond just ping pong. What would you use it for? It’s always interesting to see what students are working on; core concepts from these experiments tend to make their way into their professional lives later on. Maybe they’ll even take this project to the next level and build an actual real, working ping pong robot to work with their scoring system!

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Spectrum Analyzer on the Cheap

Provided you have an NTSC-compatible TV you can build yourself a really inexpensive spectrum analyzer. From there you just need one trivial piece of hardware to complete this build. [Bruce Land] has come up with a spectrum analyzer that shouldn’t cost any more than $5, if that’s what’s been keeping you from adding this tool to your workbench!

The spectrum analyzer is based on a PIC32 microcontroller which was previously proven in his Oscilloscope project. [Bruce] has managed to squeeze quite a bit out of this robust chip; the spectrum analyzer has 450 kHz bandwidth and runs a 256 Hz TV display and can output over 30 updates per second. The microcontroller runs the Fast Fourier Transform (FFT) to do calculations, with great results.

[Bruce] notes that the project was based on TV framework from another project, and that the FFT was added on top of that. Be sure to check out the source code on the project site if you’ve been on the hunt for an inexpensive spectrum analyzer, and if you need something with more processing power but only slightly more money, check out the FFT that runs on the Raspberry Pi’s GPU.

ATtiny85 Does Over The Air NTSC

[CNLohr] has made a habit of using ATtiny microcontrollers for everything, and one of his most popular projects is using an ATTiny85 to generate NTSC video. With a $2 microcontroller and eight pins, [CNLohr] can put text and simple graphics on any TV. He’s back at it again, only this time the microcontroller isn’t plugged into the TV.

The ATtiny in this project is overclocked to 30MHz or so using the on-chip PLL. That, plus a few wires of sufficient length means this chip can generate and broadcast NTSC video.

[CNLohr] mentions that it should be possible to use this board to transmit closed captioning directly to a TV. If you’re looking for the simplest way to display text on a monitor with an AVR, there ‘ya go: a microcontroller and two wires. He’s unable to actually test this, as he lost the remote for his tiny TV from the turn of the millennium. Because there’s no way for [CNLohr] to enable closed captioning on his TV, he can’t build the obvious application for this circuit – a closed caption Twitter bot. That doesn’t mean you can’t.

Video below.

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