The duel of the dual-layer DVD formats
The DVD+RW camp, which includes Hewlett-Packard, Dell and Philips, plans to put so-called “double-layer” DVD recording devices on the market by next spring. Discs on these systems are expected to hold 8.5GB, or four hours of DVD-quality video. That’s about the same amount as the DVDs studios use to issue movies.
But the so-called “dash” camp promoting the DVD-R and DVD-RW formats also is working on dual-layer recording, which involves writing data on two separate surfaces. And unlike in the videotape-standard battle between VHS and Betamax, “plus” and “dash” may be able to coexist for some time to come.
“I do believe that the plus guys are going to get there first,” said Robert DeMoulin, marketing manager for branded optical products at Sony. Sony, like some other manufacturers, makes DVD recorders that combine both plus and dash technology.
Retail movies sold on DVDs typically come with data written on two layers. But the commercial process involves “stamping” the discs rather than burning spots with a laser.
Dual-layer DVD-R products are slated to come out sometime next year, said Andy Parsons, senior vice president in the business solutions division of Pioneer Electronics USA. But he said dual-layer recording, no matter what the format, faces hurdles. One is the importance of fully recording both layers of a dual-layer disc, he said. If that doesn’t occur, Parsons said, some DVD players might behave unpredictably, for instance by causing a momentary interruption of the program.
The dual-layer DVD+R specification does not require the entire disc to be recorded. Philips’ Driessen said that if one layer of a dual-layer DVD+R has a recorded signal at a particular point on the disc, the other layer must have a matching signal; otherwise, a player may detect an error. For example, if one layer has 4GBs of data recorded, the other layer must have 4GB as well. But he said blank space may be left at the edge of the DVD without any playback problems.
