By Ben Metcalfe BBC News Online

File-sharing over the internet was a real headache for the record industry in 2001. But this year, the focus looks set to shift to the film industry.

The technology that enabled music tracks to be compressed to a size that could be sent over the internet is now being used to put whole movies on to the net.

One of the most common is called DIVX, a highly versatile video compression technology based on the MPEG-4 format.

However, it can also be used to turn a DVD film into a small enough file to fit on a blank CD.

Sharing films

Downloading movies has been popular with Americans wired up to broadband.

It has not quite reached the proportions of music file-sharing. But there are enough movies being made available by hardcore enthusiasts that you are likely to find your favourite blockbuster available for download.

Like copying a music album to MP3, creating a compressed film is as simple as loading a DVD movie and running one of the many freely available software "rippers".

For those living in countries outside the US where broadband is available, downloading a movie from the net is particularly enticing.

Many of the newest films available have not yet received a worldwide release. More often than not, this is because in the US, DVDs are sold to the public shortly after the cinemas stop showing the film.

However, there are even cases where disgruntled film industry workers have managed to obtain a digitised version of a film and put it out on to the web before its release in the US.

PC screen

Technology has not only made sharing films much easier. It has also opened up other means of watching movies on a computer.

VHS tapes: The way we were

Having successfully downloaded the movie to your computer, one is obviously left with the problem of storing and managing what is understandably a large file.

DIVX technology is able to compress a movie to such an extent that the film can fit on to a recordable CD, with little loss in quality.

The encoding software automatically selects the compression rate needed to create the 700 MB file that would fit on a CD.

The resulting file is about 15% of the size of the original DVD.

This means you can burn the file straight on to a cheap, blank, recordable CD and watch the movie on any computer, even those that do not have a DVD drive.

This is achieved by using the large amount of processing power available on a computer to compress the data.

During playback an equally large amount of processing power is needed to convert the compressed film into something viewable.

DVDs use a much smaller level of compression, which allows them to play in devices that do not have a massive amount of processing power such as a home DVD player.

Stopping piracy

Independent filmmakers are already releasing their work in DIVX format.

Like the record industry, work is under way to modify the technology to include a "secure wrapper" so that internet users can legally download Hollywood movies after paying a subscription charge.

Once downloaded, these modified movie files might only play for a time-limited period, just like renting a video.

At the moment, blocks put on DVDs to stop them being copied are simply circumvented by most DVD ripping software. It is inevitable that any further measures implemented by the industry will just be hacked and evaded.

The popularity of MP3s has hit the record industry hard and not just in terms of legal fees and sales it argues it has lost.

Now it is the film industry's turn and one cannot help thinking that they are in for a rough ride.