The problem with putting a high-definition program on a standard DVD is one of storage capacity. Put simply, high-definition programming requires more data storage space than does a standard definition movie.
A 135-minute standard-definition movie requires a little over 6GB of storage, which is fine for today's DVDs, which can store up to 8.5GB of data. But that same 135-minute movie in high definition requires 13GB of storage, plus another 5GB for the lossless digital audio tracks and even more storage for audio commentary tracks, foreign language tracks, and various disc extras. So we're looking at 20GB or more for a complete high-definition disc, which definitely won't fit on an 8.5GB DVD.
What's necessary, then, is a new DVD format that can store more than 20GB per disc. Enter two new and competing formats, Blu-ray Disc and HD DVD. The HD DVD format holds 30GB on a dual-layer disc, while the Blu-ray format holds a whopping 50GB on a dual-layer disc -- more than enough space on either type of disc to store a typical high definition movie.
Michael Miller is a writer and commentator on technology and digital lifestyle topics. 
