Blu-ray Vs HD DVD

High Definition has already become the next generation format, many products already support the crisp resolutions of HD 1080i but there is still one thing undecided, Blu-ray or HD DVD? Both support high definition with similar technologies but they are not compatible and require different hardware to work.

With the two formats so closely matched in this head to head battle, it is impossible to predict which one will come out on top as the leader of the next-gen’ or if we may be indeed be stuck with the two competing formats.

Both systems use a 405nm wavelength blue-violet laser, but their optics differ in two ways.

Blu-ray disc have a tighter track pitch, this is the single thread of data that spirals from the inside of the disc all the way out. Tighter means its also longer, therefore it can hold more pits (those microscopic 0s and 1s) on the same size disc as HD DVD even with a laser of the same wavelength.

The difference in track pitch results in different apertures. HD DVD has an aperture property of 0.85, the Blu-ray discs 0.65. This is what makes them technically incompatible even though they use the same laser.

The discs also have different surface layers (the clear plastic layer on the surface of the data what you get fingerprints and scratches on). Blu-ray has a very thin, 0.1mm layer to help enable the laser to focus with that 0.85 aperture, while the HD DVD uses a 0.6 mm-thick surface layer, the same as DVD.Herein lies the issues associated with the higher cost of Blu-ray discs.

Because Blu-ray discs incorporate a new surface layer, costly production facilities must be modified or replaced in order to produce the discs. The special hard coating that must also be applied to Blu-ray discs, so their surface is sufficiently resilient enough to protect the data a mere 0.1mm beneath, also drives up the cost. There is one major benefit of the Blu-ray technology, as the data layer is closer to the surface there is more room for extra layers.

So here’s the low down and specifics for the two different HD formats.

Blu-ray Vs HD DVD

HD DVD and Blu-ray can deliver hi-def video in three formats:

• 720p - 720p offers the lowest high definition pixel count, at a resolution of 1,280 x 720 pixels. Each frame is scanned on to your screen progressively, or in its entirety, which results in smooth edges during motion
• 1080i - The 1080i format has a higher resolution of 1,920 x 1,080 pixels. Picture is detailed even on large screens, but as each frame is scanned in two passes, 1080i can sometimes display jagged edges around moving objects
• 1080p - This is the best of the lot, the highest resolution with progressive scan. But currently not every HD display is able to display this format and you’ll need really big screen to fully appreciate the superior image quality

Capacity
Blu-Ray		HD DVD
ROM single layer: ROM dual layer: RW single layer: RW dual layer: Highest test: Theoretical limit:	23.3 / 25GB 46.6 / 50GB 23.3 / 25 / 27GB 46.6 / 50 / 54GB 100GB 200GB	Single layer: Dual layer: Highest test: Theoretical limit:	15GB 30GB 45GB 60GB

Although most companies have sided with either Blu-ray or HD DVD, there are some examples that don’t follow suit. The Nichi Corporation, who holds the design patents to the Blu-ray’s laser system, sits as an associate member of the HD DVD Promotion Group and even though Apple sits on the Blu-ray Board of Directors, its DVD Studio Pro software supports authoring HD DVD media.

Format founders
Blu-Ray	HD DVD
Sony Corporation Royal Philips Electronics	Toshiba Corporation Hitachi Corporation

Studios (movie and game) listed as supporting members
Blu-Ray	HD DVD
20th Century Fox Buena Vista Home Entertainment Electronic Arts MGM Studios Paramount Pictures Sony Pictures Entertainment The Walt Disney Company Vivendi Universal Games Warner Bros.	Buena Vista Home Entertainment New Line Cinema Paramount Pictures The Walt Disney Company Universal Studios Warner Bros.