First announced at this year’s Consumer Electronics Show (CES), the Total HD is a disc that’s capable of playing on both Blu-ray and HD DVD players (one format on each side). It was initially due to launch in the second half of 2007, but was then delayed until the beginning of 2008. It is now on indefinite hold.

While studios will no doubt say it’s so they can offer the best possible video and audio, it smacks of a rather cynical marketing ploy to us. When DVDs fi rst came out, it wasn’t uncommon for a film to come with no extras at all (also known as a vanilla disc). That way, when extras were later made available for special editions, there was more chance of consumers ‘double dipping’ and picking the more loaded release. Considering that many Blu-ray and HD DVDs have been released numerous times on DVD, it’s somewhat criminal that all these extras aren’t made available. Some would argue that it’s picture and sound quality that’s most important. But hey, that’s why fi lms normally come with a second disc.

VMD stands for Versatile Media Disc and is the third high-def disc format to appear. Created by UK technology fi rm New Medium Enterprise, its discs can currently store 15-20GB on a single layer. While no major American fi lm studios are currently supporting the new format, New Medium Enterprise has struck a European deal with Monolith Films.

Encoding is a way of transferring specifi c information from one format to another. Both formats currently use either VC-1, MPEG-2 or MPEG-4 (H.264).

While Blu-rays and HD DVDs can be bought from a variety of retail stores, including Blockbuster (Blu-ray only), Gamestation, Virgin, Game and HMV, they often tend to feature highly inflated prices. Your best option is to use internet sites like play.com, amazon.co.uk or movietyme.com.

Compression is essentially a way of encoding information by using fewer bits than an un-encoded version would use. It can take the form of zipped fi les on a computer but, as far as high-defi nition is concerned, it is used to compress both video and audio (although audio compression is more common on HD DVDs).

All HD DVDs are Region Free, so it’s possible to buy films from anywhere in the world and not have to worry about them not working. This is particularly handy for keen moviegoers, as you can sometimes buy movies around the same time they appear in UK cinemas.

Currently, both Blu-ray and HD DVD use the following three different codecs: MPEG-2, VC-1 and H.264/AVC. Initial Blu-ray releases appeared on MPEG-2s, while the majority of HD DVDs tend to use Microsoft’s VC-1.