[quote name='shipwreck']Well, yes HD-DVD and Blu-Ray are much larger storage mediums. HD is up to 60 GB and Blu-Ray is up to 200 GB dual layered (I hope I remembered those correctly off the top of my head). But they also provide the means for DVDs to actually be in Hi-Def. Currently progressive scan DVD's only support 480p. HD-DVD and Blu-Ray will allow for support of 720p and 1080i/1080p.[/QUOTE]
www.blu-ray.com
How much data can you fit on a Blu-ray disc?
A single-layer disc can fit 23.3GB, 25GB or 27GB.
A dual-layer disc can fit 46.6GB, 50GB or 54GB.
To ensure that the Blu-ray Disc format is easily extendable (future-proof) it also includes support for multi-layer discs, which should allow the storage capacity to be increased to 100GB-200GB (25GB per layer) in the future simply by adding more layers to the discs.
http://www.disctronics.co.uk/technology/hddvd/
An alternative version has been developed by Toshiba and NEC and a specification for the pre-recorded version has been approved by the DVD Forum. The original name was AOD (Advanced Optical Disc). There are three versions in development.
1. HD DVD-ROM discs are pre-recorded and offer a capacity of 15 GB per layer per side, offering capacities up to 30 GB per side or 60 GB per disc. These can be used for distributing HD movies.
2. HD DVD-RW discs are re-writable and can be used to record 20 GB per side for re-writable versions.
3. HD DVD-R discs are write-once recordable discs with a capacity of 15 GB per side.
DVDs are not in HD format now b/c there isn;t enough room on the disk and movies are not filmed with HD cameras yet. The new HD DVD formats allow grater room to hold movies in the HD format, since they take more space.