Simple PAL/NTSC Video Signal Generator

[Mike Warren]

I need to generate a signal that can be switched between PAL and NTSC as simply and cheaply as possible. This is just for quickly checking which format various video monitors support. Video quality is not important. All it needs to do is generate some sort of recognisable image. I don't even really need to have the colour information, although it would be nice if it was a colour picture, perhaps colour bars or a grid. A blue screen is not practical since many monitors switch to blue when there is no signal and it wouldn't be easy to tell if there was a signal or not.

I thought of using a small AVR or PIC and a few passives, but don't really want to spend the sort of time needed to write the code, so I thought I'd ask here if anyone has a simple idea. Maybe someone has already done this and can share the code?

Even a cheap eBay format converter or similar, if there's any that produce some sort of picture (perhaps a menu) when there's no input. I even looked at cheap cameras, but I can't find any that can be switched between PAL and NTSC.

This is only a one-off device for internal use.

[amyk]

Maybe this might inspire you: http://www.linusakesson.net/scene/phasor/
http://hackaday.com/2013/03/27/color-ntsc-video-directly-from-an-avr-chip/

[David_AVD]

Maybe two cheap cameras and a switch?   

[netdudeuk]

Maybe this might inspire you: http://www.linusakesson.net/scene/phasor/
http://hackaday.com/2013/03/27/color-ntsc-video-directly-from-an-avr-chip/

You might like to check out the guy in the second link. He has some great projects on his YouTube channel.

[woodchips]

With the stopping of analogue TV there are any number of bits of TV test equipment around for next to nothing, probably the easiest way of solving the problem.

[Psi]

You could get a minim OSD board. They cost like $20 and use a MAXIM OSD chip plus arduino compatible atmega. (i think they are using fake maxim chips, but it doesn't matter).

The board draws text/numbers on top of a composite video signal for use in RC planes, so you see some stats about speed, battery volts etc.. on top of your camera feed.

If you don't provide a input video signal the max chip generates its own "gray" background for overlaying the text on instead.
I'm not sure how the code is currently setup, i think it may autodetect PAL/NTSC, but i know the chip does have PAL and NTSC options you can set in the chips registers.
So you should be able to change/replace the code to switch between a PAL or NTSC output signal.


Another option is a reasonably good model VCR, a lot of them had switches for setting the output video standard which was independent of the input (from tuner or vhs tape). I remember my SONY one did.
Since they are pretty much worthless now you should have no problem finding one for cheap/free.

[robgambrill]

As you may know Radio Shack is having a bit of financial trouble. I recently purchased some of their Parallax P8X32A Quickstart boards for under $8.00 each.

 These propeller chips have the timing for producing video output. Check out http://letsmakerobots.com/content/video-propeller. Three resistor circuit for PAL or NTSC. VGA is possible too.

 I admit it is rather an obscure choice, but the darn thing is the cheapest thing I can think of. The bare chip can be purchased in a DIP package if you want to do a quick one-off design.

 BTW: The propeller chip is Open Source HardWare. Parallax provides the Verilog to implement one on an FPGA. They seem to support hobbyists/makers, so I would like to see them sell a lot of chips. But I think this is the only chip Parallax Semiconductor makes at the moment.

[vk6zgo]

You could probably do something with an old DVD player,too.

The easy way of telling the difference between PAL & NTSC is to poke some PAL into it (possibly from that old DVD player).
If it doesn't give a colour pix it is probably NTSC (OK,it could be SECAM).

Another way is to open the Monitor & have a look for a 4.433MHz crystal &,particularly, a delay line.
NTSC doesn't have one,don't think SECAM does,either.

 If you want to make a generator,there are probably dozens of special chips that do the job you need,though,without approaching it from scratch.

[netdudeuk]

If mono is ok then there's this option that I built for another project.

http://searle.hostei.com/grant/MonitorKeyboard/index.html?mmskip=1

It does PAL and NTSC and is pretty cheap to make.

There is the Propellor option. I've bought a few of them to use for video generation amongst other things.  You could use their reference design to get something going pretty quickly but it will probably cost more than that AVR solution.  You'd also need their Prop plug or something similar to program the raw Propellor chip.

[Richard Crowley]

It wasn't actually stated, but I am assuming that Mr. Warren is asking for a composite video signal?

The Raspberry Pi SBC has a composite analog output which can be programmed to produce NTSC or PAL.
I would think that one of these would probably be the most reliable and least expensive options.
Or they are so cheap, two of them, one set for NTSC, and the other for PAL.

I am going to be working on a video switcher project that needs several test HDMI inputs.
I plan on using several RasPi boards to generate static signals for test purposes.
I don't know of any more cost-effective way of generating static (or even dynamic) video signals.

[Mike Warren]

Thanks for all the ideas. 

The one I like the sound of most is the Raspberry Pi idea. I've been meaning to get one to have a play with, and this should be about the simplest project possible. However, using 2 of them seems a bit clunky. There's just 2 things I'm not sure of.

1/ Can it be switched between PAL and NTSC without a reboot?
2/ What sort of boot time could be expected to just display a simple bitmap (or text, if the graphic is a problem).

I guess I should just order one. If it's not suitable for this task I still want to play with one anyway.

Is this the current version?
http://au.element14.com/raspberry-pi/raspbrry-modb-512m/sbc-raspberry-pi-model-b-512mb/dp/2434669

[Richard Crowley]

The latest versions of the RasPi dropped the RCA connector used for composite video output, however the composite signal is still available on the 40-pin header I/O connector.  And the latest versions use faster processors, which have no apparent benefit to an application like a video test-pattern generator.

I believe in the original version, the RasPi does require re-booting to switch between NTSC and PAL. The design assumptions of the originators was that NTSC/PAL was a "fixed" variable dependent on what part of the planet you live in. So it is "baked in" to the operating-system parameters.

However, since the signals are software-generated, there is nothing to prevent you from hacking the code to make that a dynamic variable that could be controlled with a switch.

[deephaven]

The old ZNA234 is a single chip 625/525 line sync and video pattern generator. Only monochrome though.

Data here: http://www.mikrocontroller.net/wikifiles/9/9e/ZNA234E.pdf

[Mike Warren]

The old ZNA234 is a single chip 625/525 line sync and video pattern generator. Only monochrome though.

Data here: http://www.mikrocontroller.net/wikifiles/9/9e/ZNA234E.pdf

That does look like a very simple solution. I see there are some available on eBay.

[Mike Warren]

However, since the signals are software-generated, there is nothing to prevent you from hacking the code to make that a dynamic variable that could be controlled with a switch.

My concern is that it may require recompiling a driver or other program, which would mean I'd have to set up a dev environment (and probably Linux). Not impossible, but quite a lot of work.

I've posted some questions on the raspberrypi.org forum.

[vk6zgo]

If you produce a video signal without colour information,you will get a black & white image on the screen,with perhaps some colour artifacts if you have hit the correct colour burst frequency.

Most PAL & NTSC Monitors will produce a reasonable black & white image when fed with the other standard's video signal.

I have looked at PAL colour bars with a multi-standard Monitor.
With the Mon in:-
 NTSC,it produces a good black & white image.

SECAM,from memory,it produces a black & white image,with a slight colour cast,because the burst frequency is correct & the decoding is trying to make something of it.

On another occasion I have watched SECAM off a satellite on a PAL Monitor,which also produced  black & white with a colour cast,probably for the same reason.

If,as it appears,you are only interested in determining which Monitors are NTSC,& which are PAL,you only need a PAL source.
Apart from the DVD player I referred to earlier,you could use a TV set top box.

There are probably thousands of these lying around unused.
You can even watch the Cricket while you are testing!