Dual layer DVD R: DVD R dual disc

	Dual layer DVD R: DVD R dual disc


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Dual layer DVD R: DVD R dual disc

Dual layer DVD R products are expected to come out sometime next year. But, dual layer recording, no matter what the format, faces hurdles. One is the importance of fully recording both layers of a DVD R dual disc. If that doesn't occur, some DVD players might behave unpredictably, for instance by causing a momentary interruption of the program when using a Dual layer DVD R disc.

DVD R dual disc of 8.5GB will increase the time needed to make a full recording. The dual layer DVD R Plus specification does not require the entire disc to be recorded. If one layer of a dual layer DVD R Plus has a recorded signal at a particular point on the disc, the other layer of such a DVD R dual disc must have a matching signal; otherwise, a player may detect an error. For example, if one layer of DVD R dual disc has 4GBs of data recorded, the other layer must have 4GB as well. But, blank space may be left at the edge of the DVD without any playback problems.

Arranging for both layers of dual layer DVD R to be recorded in equal amounts is relatively easy in the case of data files of a known size. When a user records a television broadcast of unknown length, however, the drive may need to add "dummy" data in order for the DVD R dual disc to be readable in DVD players. This could mean a finalization process of up to 25 minutes. Future write speed improvements (such as 4x) will reduce this finalization time.

Dual layer DVD R Plus recording prototype created by Philips and media-maker Mitsubishi Kagaku Media uses focused light to mark areas on two dye surfaces stacked on top of each other of such DVD R dual disc. For each dye layer, reflective material sits underneath to send back light to the lens, which interprets the signal. One challenge is getting light to stop and record on the closest layer, and also to pass through it to record data on the subterranean surface of DVD R dual disc.


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