Pure BBC Video Grabbing

By Dominic Ford

Originally published in EUG #39

A couple of years back, EUG featured some digitised images submitted by Simon Pilley. I'm not quite sure of their origin, but they were almost certainly digitised on the Archimedes or PC, and then ported down to the Electron. I decided to have a go at doing something similar, except actually doing the digitisation on a BBC. The idea I had was to put a video signal from a camera into a Beeb, and expect an image to appear on the screen.

This project of mine is still very much in progress, and actually forms part of a rather larger project I'm working on to get a Beeb to take a video image from a camera mounted on a Rover, and use it to drive the Rover to a desired destination. Currently, I'm able to achieve a resolution of around 50 x 250 by grabbing a whole load of frames and compiling the results into one digital image. This does, of course, make the system useless for photographing moving objects, as it relies upon having a steady image for about a second while the grab is performed.

The demo I've submitted (on the Utilities Menu) contains a couple of sample grabs which I've done to show what the result looks like. They don't look very good close-up, so stand back from the screen a bit to see the images. If you can't work out what they are (which you probably won't be able to!), they are:

  1. A BBC Micro keyboard (the function keys show up well...)
  2. A building

The quality of these grabs isn't that great compared to those done by Simon Pilley but remember - this is purely Beeb produce! I'm currently working on a more sophisticated system which will take pictures at 128 x 250 resolution, which will look considerably better and it will draw all of the grab data from one frame, allowing moving objects to be grabbed.

I'll send some better pictures when I've built my improved capture system, and will probably include some more detailed information of my Rover project. The new capture system will involve fitting a PCB inside a BBC (and an Elk version might be possible as well), so it might be possible to produce a whole load of video grabber PCBs and sell them to EUG members along with software to do the grabs (possibly £25 or so).

Please do write into EUG if you're interested in the idea, essentially as I'm going to see if there's any response before I start contacting any potential manufacturers.

Dominic Ford, EUG #39