SHOULD people who have bought DVDs legally be allowed to make digital copies of them for their own use? Any reasonable person would say yes. In copyright terms, that ought to be considered “fair use”. The law, however, presently says otherwise.

In America the Audio Home Recording Act of 1992 considers it fair use for people to record copyrighted radio broadcasts for personal use. But the act says nothing about making digital recordings; and ripping copyrighted music tracks off CDs and storing them on iPods has now become an everyday occurrence. Apple would be in serious difficulty if people were prevented from transferring their own CDs to their iPods. Indeed, the software Apple gives away to iPod customers is designed to let them do just that. Yet it is probably illegal.

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One reason cited by people who believe they are entitled to make copies of any copyrighted material is security. A backup copy is needed, they say, in case a rare or favourite DVD is attacked by “disc rot” or gets badly scratched.

They are being disingenuous. Optical discs are not indestructible, but they are remarkably robust. Certainly, the adhesive used to bond the layers within the platter can lift, causing the aluminium data-layer below to become oxidised and patchy. But the solution is simple: keep all optical discs out of direct sunlight.

Meanwhile dust, fingerprints and even scratches can usually be removed by wiping the polycarbonate disc with a polyester cloth dipped in dilute washing-up liquid, and then rinsing with rubbing alcohol or methylated spirits.

Just remember to wipe the disc radially—from the centre to the edge. Wiping with a circular motion—parallel to the direction the data are laid down—can create microscopic blemishes over the Hamming error-correction codes. The picture can then become jerky or freeze as the video player stumbles across the patch of corrupted data.

In an act of desperation, your correspondent once used toothpaste to rub out deep gouges on a Laser Disc. The unplayable disc was restored to life, and subsequently replayed many times with never so much as a flicker.

The polymer coating of a Blu-ray Disc makes it even more durable than a DVD. Though little more than half a millimetre thick, it can withstand a surprising amount of abuse. It even stands up to a screwdriver attack.

Another excuse used by those who would copy DVDs is convenience—to have copies of favourite films on a laptop while away from home. Maybe, but your correspondent thinks it is easier to take the original discs with him. A better case can be made for copying DVDs onto a dedicated home-server, especially if it is hooked up to a wide-screen television using a secure cable.

Copying DVDs for such purposes may make life easier, but it is almost always against the law. With every DVD sold in America, both the packaging and the introduction to the video itself clearly state that unauthorised reproduction, distribution or exhibition is illegal. To be more specific, the Digital Millennium Copyright Act of 1998 makes it a crime to circumvent measures that control access to the copyrighted material.

Unfortunately, the copyright protection on DVDs is so pathetic that it positively invites piracy. The encryption method known as Content Scrambling System (CSS) was first cracked in 1999 by Jon Johansen, a Norwegian programmer. In a few short lines of elegant code he called DeCSS, Mr Johansen showed the world how utterly useless the encryption was. Ever since, free software tools with names like HandBrake, DVDFab and DVD Shrink have circulated the web for copying the contents of DVDs onto hard-drives and recordable discs.

The one way you can legally copy a DVD, at least for the moment, is to buy one of the $10,000 home-server and player combos beloved by Hollywood moguls and made by a Silicon Valley firm called Kaleidescape.

A Kaleidescape server works by ripping the tracks off an owner's collection of CDs and DVDs and storing them on the digital jukebox's huge hard-drive. The digital content is then encrypted and fed to various screens and speakers around the home by a secure cable.

Ironically, Kaleidescape was sued several years ago by the film industry's friends in theDVD Content Control Association for breaching its CSS licence. In its defence, Kaleidescape claimed that content distributed this way was even safer than it was on the original DVDs. The judge not only agreed, but could find no breach of the CSS licence either. The Content Control Association is appealing against the ruling.

RealNetworks, a digital media company that pioneered much of the technology for streaming music and video from the web, has pinned its defence in court this week on the Kaleidescape ruling. Last October a group of Hollywood studios sued the Seattle firm for the way RealDVD, a $30 software program, makes copying DVDs to a PC's hard-drive a simple one-click affair, busting the CSS digital-rights-management system wide open and encouraging flagrant piracy in the process.

Not true, claims the company. RealDVD keeps the encryption intact as it copies everything—CSS included—to a PC's hard-drive, and then wraps the lot up in an iTunes form of digital rights management. Lawyers for the firm have framed the debate in terms of fair use, as the software not only maintains the CSS encryption but also locks the copies of the DVD onto the receiving PC's hard-drive for the owner's private use.

But why, might our reasonable person ask, would RealNetworks go out of its way to provoke the Hollywood studios, who rely on DVD sales for most of their revenue these days? It is not as though a $30 program, sold in direct competition with a dozen well-established freebies from the internet, is going to make any significant difference to the media company's sagging bottom line.

The answer can only be that RealNetworks has far bigger fish to fry than mere backup software for DVDs. Under questioning in court this week, the company was forced to reveal its long-term plans for the technology.

It seems that RealNetworks wants to turn its handiwork, code-named Facet, into a “TiVo for DVDs”—and do for video what MP3 players have done for audio. Apparently, the company has contracts with set-top-box makers in Asia awaiting the go-ahead. If the San Francisco court rules in its favour, RealNetworks could have its $300 version of the formidably expensive Kaleidescape jukebox out by next Christmas.

There is just one problem: the federal judge hearing the present case is Marilyn Hall Patel, who ruled against Napster in 2001—and put a stop, albeit briefly, to peer-to-peer sharing of MP3 music files over the internet.