BitTorrent is a special file sharing protocol designed to transfer very large files to lots of people simultaneously. Unlike the more common peer-to-peer networks Kazaa, Gnutella and eDonkey, where you would connect to a single server to download a particular file, BitTorrent allows you to gather pieces of a file from many different servers while at the same time making that file available for other people to download.

By spreading the load across many servers, BitTorrent can continue downloading a file without interruption, even if some of the servers suddenly go offline. And because a file is delivered in pieces, it must already know how to stitch a file back together and to identify which parts are missing, so if your computer or connection fails, you can easily resume the download where it left off.

However, there is quite a bit of negotiation required to manage all these connections, not to mention the extra overhead of having to upload while you are downloading, so BitTorrent may not be suitable for files less than about 100MB, when a direct connection to a fast file server will be more efficient. Since audio files are typically less than 10MB each, the peer-to-peer networks will continue to be your best bet for mp3 files. On the other hand, even the smallest feature film cannot be compressed into a file less than about 600mb without severely damaging its quality, so this makes BitTorrent especially attractive for distributing DVD and HDTV files.

DVD File Formats

Feature film DVDs consist of a lot of files of varying types, but the most important ones, the actual movie itself, is in the VIDEO_TS folder, which usually contains more than one version of the complete movie due to screen size options and other add-ons. Although you could just copy these files to your hard-drive, it would be much better to use a program like MacTheRipper to extract only what you really need to see the movie (widescreen only, no menus, commentaries and other options) since a typical VIDEO_TS folder has over 7GB of files.

And even then, you will still have over 3GB of files, which would take more 20 hours to download over the average dsl/broadband connection, so very often these VIDEO_TS files will be combined, re-encoded and compressed into another format such that an entire movie will be around 1GB or less. Unfortunately, there are many ways to do this and the result of most of them is something that is very hard, if not impossible, to view on a Macintosh.

But there are two formats, called DivX and XivD, that produce a single, less than 1GB file, which after installing two free plugins, will play beautifully in Quicktime 6. Although neither of these formats will obtain the full quality of the original DVD, regardless of any claims to the contrary, being able to download a feature length movie as a single file in as little as 4 hours, or your favorite TV show in less than two hours, is well worth a slight reduction in quality.