YOU’RE PROBABLY AWARE that nowadays a lot of pre-recorded video software is "copy pro-tected", to stop people from making their own pirate copies. In principle that’s fair enough, too – having spent millions of bucks making a movie, the producers are entitled to get a fair return on their investment.

What complicates the situation is that the system that’s used to prevent copying involves adding extra "dancing pulses" to the normal video signal. Unfortunately, this can stop quite a few TV sets and projectors from displaying a steady picture during legitimate viewing.

In particular, the extra pulses can cause problems with large-screen TVs that display the picture at 100 fields per second (100Hz) to reduce flicker and also with projectors that perform line and pixel doubling to improve picture clarity. They can cause problems with older conventional TV sets, too.

If you have one of these sets or projectors, often the only way to get a steady picture is to somehow remove those extra pulses. The idea is to "clean up" the video and let the set’s sync circuitry do its normal job without interference. And that’s exactly what this little project is designed to do.

Note that once the offending pulses are removed, it may also become possible to record the video. However, we want to stress that this project is NOT designed to allow recording – it’s intended purely to allow you to achieve stable and steady pictures for viewing. It is illegal to record copyright material and there are heavy penalties for doing this. We must therefore warn you specifically against using the project to do so.

As well as removing most of the copy protection pulses, Dr Video also allows you to apply a small amount of high-frequency boost to the video, to "sharpen" the picture a little when you’re watching movies on older VHS tapes (which are often a little "soft"). However, you can switch off this sharpening when it’s not needed – when you’re watching DVDs, for example (these are usually quite sharp enough already).

Dr Video is housed in a compact low-profile instrument box, and runs from a nominal 12V DC source – such as a battery or plugpack. You should also be able to build it for considerably less than other stabilisers.