How to display RGBHV video on a Laptop Computer

[Valinote]

I would like to take the 5 signal RGBHV output from an 8" color 256 x 256 dot resolution screen and display it on my laptop computer. The signal has the following characteristics:

Horizontal Sync = 15.75 KHz
Vertical Sync = 60 Hz
Dot Clock - 5.545 MHz

How do I convert the RGBHV to get it intp my laptop? Is there a PCMCIA card that would do this, or a converter box that would allow me to input to the one of the input ports on my laptop? I don't have a video "in". I've posed this question on several other forums and have received no response, so any advice you can provide would be greatly appreciated.

-Steve D

[Alan69]

That's a fairly tall order for straight into a computer.

First, see if you have access to that signal before it's RGBHV. Is it an NTSC source and then split into RGBHV for the screen display? If so the NTSC video signal would be easier to get into the computer on the video in of a capture card or similar. VGA to video converter might work, but VGA is twice that frequency and most won't go down to 15 KHz. Can't hurt to read some specs and see if anyone makes one that will.

If you only have access to the RGBHV and have to get this in, there is the easy method, cam the screen. Of course works best if it's offline stuff so you can do it once and be done. If it has to be live it's a little unwieldy.

If you've got to do it, fastest/cheapest/easiest thing will be to find an Amiga video converter, and put in the signals and power it yourself. Amigas had RGBHV at NTSC timings, so people wanting to get the Amiga picture onto a TV screen used these. Be careful not to get a genlock. They do a similar thing, but sync the Amiga picture up to an external video signal, and would likely actually require an Amiga and/or external NTSC source to run. If you get just the video converter, you should be able to power it, put RGBHV signal in on the right pins and get NTSC out. Getting NTSC into the laptop will then be relatively easy, should be lots of PCMCIA and USB options for that.

Likely there is not a direct solution, and if you find one it won't be affordable. The above will be relatively cheap for the Amiga part, were $20-$50 back when the Amiga was dying out. Likely around that now, tons were made..

LOL googled and hit your post on AVS. Just so you know your older fish finder output is almost guaranteed to have been made to drive an Amiga style NTSC RBG monitor. Older NEC multisyncs that can go down to 15.75 KHz would also work.

Just a warning, RGB like this could do 80 columns of text easily. After converting to NTSC and back on the laptop it may be hard to read. If it's mostly picture you want it should still be useful. I'd get an Amiga monitor first and hook it up, make sure the video is there and looks like it'll be useful etc before working on a final solution, then sell the monitor back off. If you know a lot of people with computers, likely someone you know has one in a closet still..


At least it's something to start with..
Alan

[Alan69]

BTW the dot clock frequency is high for NTSC, but the sync timings are right. This output was definitely made for an NTSC scan monitor, and it'll degrade with the double conversion. Not a common thing to do especially these days, anything to do it directly would be an engineering level tool and probably quite expensive.

Hmm if they were only doing 256x256 on the LCD and put the same resolution out the video, they weren't using that video output to it's fullest extent, and were only driving that frequency to run a standard high res RGB video monitor. Likely it will still look ok even with the double conversion, unless they were showing more info on that output.

[Valinote]

Alan, thank you so much for the comeback. I noticed several Amiga A520 RF composite video modulators for sale on Ebay; is that the video converter you are referring to? I am using my laptop on my boat with a rooftop USB GSP receiver as a Chartplotter/Mapping device. I thought it would be nice to also be able to view the output of my Raytheon Fishfinder on the larger screen of the laptop. If I can't find a reasonably priced solution, it might be more trouble and expense than it's worth. Thank you kindly for your learned advice!

-Steve D

[Alan69]

Yes. Been a while since I've looked at one, RF out the back, but video/audio out the rear side. It was powered through the 23 pin Dsub video port on the Amiga. Here's what you'd have to do:

Cut down a DB25 to make a DB23 (easiest way, hard to find DB23 pin connectors)
Hook up RGBHV and ground from the finder.
Get a power supply on the right pins.

This should get you video output, easy to hook to inputs on any TV, monitor, VCR etc to make sure it works to here. Looks like it'd only be $20 or so, and a few for the connector and power supply, and a little work hooking things up.

If that works, should be easy enough to get video in on your laptop. That is assuming it is a newer laptop, and at least has a cardbus PCMCIA for a video adapter of some sort. Get something with A/V in, while you could use the RF out and an RF tuner, you'll lose even more doing that. RF would be a last resort if it was the only way to get video in on your laptop.

Video out is easy, video in is a little more difficult on a laptop. I have an old compaq armada, has video out right on the back, but its PCMCIA isn't cardbus, doubt I could even get video into it. As long as your laptop is a little newer, you should be able to find some sort of video input device for it.

http://search.ebay.com/search/search.dll?from=R40&satitle=pcmcia+video&category0=


Seems like most cards on Ebay have video in not just RF, so if your laptop can use one of these you'd be good. Looks like $40ish after shipping, so $60ish or a little more with the A520 and a little work wiring it up. But of course again get the A520 first and wire it up to something else, make sure everything else is good before buying the video card. Should work, but there can be so many gotchas with something like this. There are also other RF/video modulators out there, from the era when computers were going RGB but RGB monitors were more expensive, but the A520 was common and cheap, so probably still the most common..

$20 or so to see, then $40 more to get it where you want it. Not exactly super cheap, but maybe reasonable enough to have them at the same spot.. And NP, I do electronics and used to use Amigas and have done similar hookups, so the answer was easy enough off hand.

Alan