Playing without paying

Electronics Times, Nov 20, 2000

Danny Birchall looks at how every Internet user is potentially a pirate

Across the world, Internet users are downloading music and films without paying for them. New Internet applications are making it possible to trade copyrighted material easily and anonymously. And the industry claims that, unless this is checked, the future of recorded music and film does not look good.

What makes digital piracy special, and why is it such a threat?

Digital piracy is unique in that it suffers no copy degradation. VHS cassettes rarely survive beyond a third generation copy and a tape recording of a CD shows a considerable loss in fidelity to the original. A digital copy, by contrast, is identical to the original, and - more importantly - infinitely copiable. The recent explosion in home Internet use has given people a global network with which to swap files containing copyrighted music and films.

Three things have made digital piracy prevalent rather than merely possible. The first is the proliferation of digital originals. Digital audio has been around in the form of CDs since the early 1980s, but only since the advent of CD-rom drives in PCs has it been possible for a home user to access the data that makes up the music.

Digital films on DVD have been accompanied much more quickly by DVD-rom drives in PCs, useful both for playing films onscreen and for their large data storage capacity.

While the digital audio on a CD is made up of an unencrypted and uncompressed audio file, the digital video on a DVD is both compressed - with the MPEG2 video codec - and protected by the Content Scrambling System (CSS). Each commercially released DVD contains software `locking' keys which correspond to `unlocking' keys, licensed by the DVD Forum to the makers of DVD players, at a cost of tens of thousands of dollars.

CSS was designed to prevent access to unencrypted video and to enforce the `region coding' system. But in October 1999, a group of users of the Linux operating system developed a utility called DeCSS. By listing all possible unlocking keys, DeCSS allows access to the MPEG2 file on the disc. While the original purpose of DeCSS was to provide the basis of a freeware Linux DVD player, it also opened the door to thousands of pirates to access the raw video itself.

Both MPEG2 and raw WAV files are too big to do much with by themselves - even with a broadband connection. The second enabler of digital piracy is compression technology that pushes audio and video into smaller spaces, making it easier to store and exchange across networks.

The global favourite in audio compression is MP3. This `psycho- acoustic' compression method samples at a similar rate to CD audio and uses a complex set of algorithms, based on human hearing, to filter out sounds which cannot be heard, and discards the data containing them. Typically, a 50Mbyte WAV file can be reduced to 4 or 5Mbyte. Hundreds of songs can be stored on a single CD and swapped easily between Internet users. MP3 encoders are of variable quality but widely available and easy to use.

Video compression is more complex. Since DVD's adoption of the MPEG2 codec, MPEG4 has been developed, which can compress the same video as MPEG2 into a smaller space at a similar level of quality.

A hackers' codec named DivX, based on MPEG4, can compress several gigabytes of MPEG2 into a VHS-quality file in less than 600Mbyte, small enough to transfer over a broadband connection. Creating DivX from MPEG2 requires a powerful PC as well as a collection of tools, but playback only needs a plug-in for Windows Media Player.

The third part of the piracy equation is file sharing. Making pirated songs and videos available on the Web is risky: once a site distributing illegal copies is found it can usually be shut down. Trading in pirated software has existed for many years, but tracking down temporary FTP sites has little mass appeal.

The breakthrough in file sharing came with the Napster application, which allows users to swap MP3 files directly from one PC hard disk to another. Having `ripped' any number of songs to MP3 files on your PC, you can log on to the Napster network and search other users' collections. Napster maintains central servers that upload your MP3 file list for others to search. When you find a track that you want, you select it and Napster links you directly with another user's PC. Meanwhile, other users download songs from your PC.

Dozens of similar file-sharing networks have followed in Napster's wake. Most, unlike Napster, are not limited to MP3 files, and allow you to swap music, films, pictures and any other kind of file. The Scour network allows the transfer of DivX films and, like Napster, uses central servers.

Gnutella uses a different model of file sharing, activated by connecting to another client running Gnutella and through that to other clients. While wasteful of bandwidth, this model is completely decentralised. And in the wake of Napster, Scour and Gnutella, dozens of imitators and clones have sprung up, customising the principle for different platforms, file types and users.