It's that small logo on Blu-ray cases: BD-Live. BD-what? BD-Live is a system that allows you to download from the internet and enjoy interactive content - via your Blu-ray player! We ask the question: what is BD-Live and what can it offer you?

This is the logo to look out for: This Blu-ray disc allows you to download BD-Live material.

When you buy a new Blu-ray player, the biggest issues will be how to connect it up and how to get to grips with its features. Check out our player reviews for more tips on setting up the device. But once you've got it all working and you've settled down for a couple of movies, you might find time to wonder what all this BD-Live fuss is about. Well, let's take a look.

Before we even get started, you'll need an internet connection and a player with a network interface. You'll also need a built-in hard disk or external storage with a capacity of at least one gigabyte, so that you can also store downloaded content. But you needn't worry too much about these requirements: Almost all new players now have a network interface - examples include the Pioneer BDP-320 and the Samsung BD-P 3600.

The Pioneer BDP-320: a cheap, elegant player with superb picture-quality and BD-Live support.

Oh, and another thing: The Blu-ray disc must have a BD-Live function - otherwise, this obviously isn't going to work! Far from all discs offer this function, but the number is at least growing. You'll find BD-Live on, for example, "Step Brothers", or "Half Past Dead".

"Step Brothers" is one example of a Blu-ray with BD-Live.

It's important to note that BD-Live doesn't normally start by itself - you'll have to actively select it in the menu first. The player therefore only creates the connection on request.

BD-Live is a new, interactive, and still-quite-exclusive Blu-ray feature. Introduced as part of Blu-ray profile 2.0, it still isn't used on all discs. BD-Live allows the viewer to download and store exclusive content such as actors' profiles, trailers, background stories, or even games related to the movie. And there's a pleasant side effect to having an internet connection: Many Blu-ray players can download updates for their software when they become available - this saves you the bother of manually downloading the software and burning it onto a CD.

Chatting in the home theater? Not a problem with the Blu-ray "The Da Vinci Code"! But is it really a good idea?

One interactive feature is the "CineChat" function, which first appeared on Sony's Blu-ray release of "The Da Vinci Code". Here, viewers can use BD-Live's internet connection to chat with other viewers and exchange thoughts on the movie as it progresses. The text comments are sent via an on-screen keyboard or via the home PC. This is also possible, for example, on the technically outstanding Blu-ray release of "The International".

An example of a BD-Live start page.

Opinions vary widely as to whether this is a sensible feature or not. We doubt that it'll be used often; surely most viewers want to give the movie their full concentration. You can also cast doubt on the online extras in vampire flick "Twilight": Do you really want to see the "vampire weather" for local cities, so that you can know exactly when the sun goes down and dusk sets in? Does anyone really need a "vampire test", which uses 16 questions to determine whether a person is a vampire or not? We're not sure, but we did at least establish - surprise, surprise - that we're not bloodsuckers.

When does the sun set in your city? Find out on the Blu-ray "Twilight"!