As we all know, DVDs are easily damaged and aren't quite as forgiving as CDs when scratched. Making a backup copy of a DVD allows you to keep your original safely stored in pristine condition away from harm while the disposable copy takes the abuse. It sounds pretty simple, doesn't it?

The problem is that some people copy movies that don't belong to them. In order to try to curb the illegal copying of movies, the Digital Millennium Copyright Act (DMCA) law was enacted in 1998 making it illegal (in the United States) to circumvent any copy protection system. It might sound reasonable; after all, movie studios have a right to protect their investment. However, what did it really accomplish? The world's piracy problem continues to run wild and the DMCA has done little to curb it. I'm sure there are one or two very malicious pirates who are rotting in a minimum security prison somewhere right now thanks to the DCMA, but what about the rest of us?

The problem with the law is that it does not contain a provision for fair use, which means that exercising your fair use rights legally has become very difficult. In order to make a backup of a DVD that you own, it's still necessary to find a way around its copy protection system. Since the DCMA has made removing all copy protection illegal, those of us who want to make a legitimate backup of our DVDs have limited options. Sadly, once again the steps taken to fight piracy hurt the legitimate law-abiding consumer far more than the pirates.

One way to get around the DMCA without risking a trip to the "big house" is to use the DVD Xpress DX2 from ADS Tech. The DX2 works by re-encoding (digitizing) the DVD directly from the analogue output of a DVD player, circumventing the whole DMCA mess. The downside of this method, of course, is that the copy is not a perfect duplicate of the original and comes with audio and video quality loss. The key question I set out to explore was whether the copy produced by the DX2 will still be acceptable.

Incidentally, there is another copy protection mechanism that the DX2 has to deal with. DVDs contain a copy protection system developed by Macrovision that is designed to prevent copying DVDs to videotape. The Macrovision system uses the "extra" lines in the NTSC signal that are used by a VCR's automatic gain control circuitry (AGC). (There are actually 525 vertical lines in NTSC, but only 480 of them are used for displaying video. The extra lines are usually used to transmit extra information such as closed captioning etc.)

Automatic gain control (AGC) is normally used to adjust the strength of a recording so that a good image is recorded. Macrovision discovered that they could ruin DVD to VHS copies by altering the extra NTSC lines so that a VCR's automatic gain control would believe that there was a signal strength problem. But because the AGC circuitry changes attempt to correct a non-existent problem, the result is a very distorted and nearly unwatchable recording. The DX2 bypasses the entire Macrovision process by not using an AGC chip and passes the Macrovision-altered NTSC lines directly through to the DVD copy, leaving the Macrovision protection intact.