MAM-A | Technology

Format comparison

Blu-ray Discs (BDs) and HD DVDs have the potential to provide the highest resolution that the current high-def video standard allows. They could even provide unprecedented audio performance by using various advanced capabilities.

Parameters	CD	DVD	DVD	BD	BD	HD-DVD	HD-DVD
Storage capacity	0.74 GB	4.7GB	9.4GB	25GB	50GB	15GB	30GB
Number of layers	single-layer	single-layer	dual-layer	single-layer	dual-layer	single-layer	dual-layer
Laser wavelength	780 nm	650nm	650nm	405nm	405nm	405nm	405nm
Numerical aperture (NA)	0,45	0.60	0.60	0.85	0.85	0.65	0.65
Diameter of laser spot on data layer, in micrometers (µm)	1.6 µm	1.1 µm	1.1 µm	0.48 µm	0.48 µm	0.62 µm	0.62 µm
Track pitch	1.6 µm	0.74 µm	0.74 µm	0.32 µm	0.32 µm	0.4 µm	0.4 µm
Minimum pit length	0.83 µm	0.40 µm	0.40 µm	0.15 µm	0.15 µm	0.204 µm	0.204 µm
Protection layer	1.2mm	0.6mm	0.6mm	0.1mm	0.1mm	0.6mm	0.6mm
Data transfer rate	1.4 Mbps	11.1Mbps	11.1Mbps	36.0Mbps	36.0Mbps	36.0Mbps	36.0Mbps
Video compression		MPEG-2	MPEG-2	MPEG-2 MPEG-4 AVC VC-1	MPEG-2 MPEG-4 AVC VC-1	MPEG-2 MPEG-4 AVC VC-1	MPEG-2 MPEG-4 AVC VC-1

	Blu Ray

Blu Ray is supported by : Sony, Dell, Hewlett-Packard, Hitachi, LG Electronics, Matsushita Electric Industrial (Panasonic), Mitsubishi Electric, Philips Electronics, Pioneer Electronics, Samsung Electronics, Sharp, TDK, and Thomson Multimedia.

	HD DVD

HD DVD is supported by Toshiba, NEC, Sanyo, and Memory-Tech. Microsoft is also supporting HD-DVD in its next version of Windows (support for Blu-ray is on the table).

All of these new features stem from two breakthroughs :

	First is an increase in the maximum data rate for streaming information off the discs - 36 megabits per second (Mbps) for both BD and HD DVD compared with 11 Mbps for standard DVD - which allows these discs to provide even better picture quality than current high-definition TV broadcasts. They'll also be able to handle several applications simultaneously, letting you do things like call up background audio and video commentaries without interrupting the movie or choose from multiple camera angles on the fly for the scene you're watching.
	The second breakthrough is far greater storage capacity than DVD. While a single-sided, single-layer DVD can hold 4.7 gigabytes (GB), a single-sided, single-layer HD DVD can hold 15 GB, and a comparable Blu-ray Disc can hold 25 GB. While each high-def format starts with a new blue laser to achieve these breakthroughs, they follow radically different paths from there.
	The key technology behind both HD DVD and Blu-ray is the blue laser, an evolutionary development of the infrared and red lasers used in CD and DVD players. The wavelength of the light coming from the blue lasers in both high-def disc formats is 405 nanometers (billionths of a meter), which is shorter than the DVD wavelength of 650 nanometers (a pure red) and nearly half the CD wavelength of 780 nanometers (in the near-visible infrared). Using a shorter laser wavelength allows a much smaller spot to be focused onto the reflective data layer.
	Using a smaller spot lets you shrink everything on the disc pro- portionally to increase the amount of data you can pack in. This happened once before with the move from the CD's infrared laser to DVD's shorter-wavelength red laser. The data-carrying pits and the spacing between revolutions of the pit trail (the "track pitch") are both substantially smaller with Blu-ray and HD DVD than they were with DVD.
	Optically, the HD DVD system was arrived at by taking a standard DVD and shrinking the dimensions of the data layer as much as the new laser wavelength allows. DVDs and HD DVDs have the same diameter, and both use the same sandwich construction made up of two 0.6-mm substrates, only one of which usually carries data, bonded with an adhesive to create a disc 1.2-mm thick (same as a CD). DVDs and HD DVDs have the same thickness as CDs to retain compatibility with current disc-loading mechanisms