Introduction
The DVD format has been hugely successful both as a home entertainment media and a computer storage format. But with the release of HDTV and ever increasing storage requirements for digital media, the need for a next generation storage format developed. Two competing formats have emerged, Blu-ray and HD-DVD. While both were developed with similar base technology, the two formats have a lot of technological and political differences. In this article, I intend to take a look at both Blu-ray and HD-DVD to give consumers an idea of what both have to offer.
Blue Lasers
The technology of the next generation DVD formats are both based upon the new blue-violet lasers. These have a beam width of 405 nanometers compared to the previous 650 nanometer red lasers used by both CD and DVD media. Because this beam is thinner, it allows more more data to be fit onto the disc. This is extremely important because the amount of data stored in a high definition video stream is much greater.
Broadcast high definition television streams have a required data bandwidth of 19.3 Mbps. Both formats have a minimum transfer rate of 36 Mbps that should provide them with sufficient data streams for quality higher than broadcast high definition. Of course, the resolution of the video and the encoding method will play various roles in the required signal bandwidth but it should be able to handle 1080p signals.
What's the Difference?
The major difference in the two formats comes from how the laser is used on the media and the media itself. The Blu-ray standard uses a lens that provides a tighter focus on the media surface. This allows the Blu-ray format to store 25GB on a single layer disc and 50GB on a double layer. The HD-DVD specification by contrast stores either 15GB of 30GB respectively.
The media is also very different between the two. The HD-DVD media was developed around existing techniques used in the production of DVD and CD discs. This allows the HD-DVD to have a lower overall cost than the Blu-ray media. On the other hand, Blu-ray specifications allow for additional layers on a single disc that can provide up to 200GB of total storage. TDK has already successfully produced this media but has not set any prices.
Multi-Format Drives?
The main reason that the original DVD recordable media wars ended was manufacturers eventually supported both formats in a single unit. This allowed the consumers to choose whichever format they wished to use based on media available and compatible with their equipment. Some companies have announced the intention to do the same thing with the Blu-ray and HD-DVD formats, but none of the initial products reaching the market have this ability.
There are several problems with supporting both formats on a single drive unit. The most notable of these has to do with the laser. While both formats use the 405nm blue-violet laster, each format uses a different type of lens unit to focus it onto the disc. In order for a drive to support both format, it will actually require multiple lasers. If the drive is also going to be backward compatible with the DVD and CD formats, this also adds an additional red laser and lens into the unit.
With all these parts, it is unlikely that many manufacturers would be willing to produce such units. The limited space of the drives to fit all of this is one factor, but more importantly is the cost. Having all the extra parts will add to the cost of the drives. With the initial computer drives costing near $500 for just a single format, not many consumers will be interested in buying.
Conclusions
The current state of affairs over the next generation DVD formats is really a wait and see. The dominant format will eventually be born out by the consumer electronics market and not the computer market. It may be a year or so though before we have a clear winner. This will have strong implications for the storage market as the majority of optical drives are now used in the production of video discs and not data storage. Why choose one format now for a computer when the other format may win out?
If however you are not concerned about using it for video and solely are using it for storage purposes, the Blu-ray format with its higher disc capacities is the clear choice. Of course, with the low cost of external hard drives, having backups of materials put onto an optical storage disc is becoming less and less common.
