Hi-Def DVD Players
Here is an article that appeared in today's N.Y. Times
Dueling Visions of a High-Definition DVD
By IAN AUSTEN
Published: April 29, 2004
With the development of high-definition television, electronics companies that make and sell DVD's realized they had a potential problem as well as an opportunity. Although the discs can hold a lot of data, they can't hold nearly enough for a movie in high-definition video format.
The capacity of conventional DVD's, 4.7 gigabytes, was originally based on the need to store a 135-minute film in slightly compressed standard video along with a few extras, said Michael Fidler, who helped introduce the technology to the United States in 1997.
But saving that same film as high-definition video with the same compression requires five times the storage space.
"There clearly was a need to develop a next-generation disc, something beyond DVD," said Mr. Fidler, now a senior vice president of Sony America.
The electronics industry has seized on the opportunity two times over. Competing groups have developed high-definition DVD formats, setting up an eventual battle between incompatible technical standards.
The two technologies, Blu-ray DVD and High-Definition DVD, store significantly more data on a disc that is the size and shape of a conventional DVD. Both use a relatively new kind of laser, one that creates blue light. But that's where the similarities end and the 21st century's version of the Beta-versus-VHS fight begins.
"Yes, the format wars," said Gerard Catapano, the manager of electronics testing at Consumer Reports magazine. "They should just pick one, but that's not going to be an easy thing."
Sony is among about a dozen companies, usually fierce rivals, that are developing the Blu-ray technology (Mr. Fidler leads Sony's Blu-ray group in the United States). Among the others are Matsushita Electric (Panasonic), Thomson (RCA and GE), LG, Philips, Pioneer, Sharp and Samsung. From the computer world, Dell and Hewlett-Packard have joined in. The HD-DVD format has been developed by Toshiba and NEC.
On conventional DVD's, binary data is stored as "pits" and "lands" - areas of high and low reflectivity - on a long spiral track on the disc. Conventional DVD players shine a red laser beam on the surface of the disc as it spins to create a stream of ones and zeroes - the data that produces lines of video to fill up a TV screen.
The blue (or, more accurately, blue-violet) light from the new lasers has a much shorter wavelength, creating a beam about one-fourth the size of a red laser. That allowed developers to shrink the size of the pits and lands correspondingly and squeeze the spiral track closer together. As a result, much more data fits on a disc of the same size.
For the developers of Blu-ray, a change in laser color wasn't the sole answer. Their new system may owe as much to chemistry as electronics.
DVD's and CD's have a thin protective layer of plastic over the substrate containing the data. Once the Blu-ray engineers had reduced the incredible shrinking pits by a factor of five, it became apparent that the coating, just six-tenths of a millimeter in thickness, was not thin enough. The slightest tilting of the disc while it was being read optically distorted the laser beam as it passed through the protective layer, leading to inaccurate data readings.
The solution came from TDK: it developed a protective layer that is just 0.1 millimeter thick but harder and more scratch-resistant than current coatings. Mr. Fidler said TDK is also developing methods to minimize fingerprints on disc surfaces, which can also distort the laser beam.
Sony has already introduced one Blu-ray product, a digital high-definition recorder that is being offered to customers of a Japanese satellite television service. It sells for about $3,000, Mr. Fidler said.
So far, HD-DVD's backers, Toshiba and NEC, have only built prototype players. (With both standards, players can be made that will also handle conventional DVD's. But the new DVD's will not be playable in existing players.)
HD-DVD's developers have shrunk the size of the pits and lands to a lesser degree and have thus managed to stay with a disc that has the same thickness as those used in current DVD players. Jodi Sally, an assistant vice president for marketing at Toshiba America, said that by not reinventing the disc, HD-DVD allows companies to burn movies onto discs with equipment they now have on hand.
The downside is lower capacity. A single-layer Blu-ray disc holds 23 gigabytes of information, while a similar HD-DVD disc has a capacity of 15 gigabytes. (Both systems can use discs that record on two layers and hold about twice as much data.)
The HD-DVD group is also considering more efficient compression software for video - including Microsoft's Windows Media 9 - to ensure that even the longest high-definition films fit on a single disc.
It is far too early to say which of the formats will win out. But Mr. Catapano, who has seen both systems demonstrated, is not sure it matters. To his eye, neither technology offers owners of high-definition television sets the same improvement in image quality that DVD's boast in comparison with videocassettes. "That's night and day," he said.
Mr. Catapano pointed out that high-definition television sets already convert standard DVD signals to something that reasonably approximates their higher image standard.
"There are improvements in the detail," he said of the two new systems. "But this is not going to be something that makes you go 'Whoa!' The step-up is not that dramatic."