4.7GB DVD-R Using Varying Specs for Light Sources
nikkeibp.asiabiztech.com
The basic approach for the next-generation digital video disc record (DVD-R) standard, featuring a single-side capacity boosted to 4.7 Gbytes, has almost been finalized.
The existing DVD-R disk is based on DVD-R Standard Ver.1, which was finalized in 1997, and has been most commonly used in authoring of play-only media. Its single-side 3.95-Gbyte capacity, however, makes it difficult to use on the proposed 4.7-Gbyte play-only disks, and therefore the development of a new standard was urgent.
There was discussion whether to continue to use the 635-nm wavelength light source defined in Ver.1, or switch to the same 650-nm source as used in DVD random-access memory (DVD-RAM) and DVD rewritable (DVD-RW) drives. The 635-nm group claimed it would provide compatibility with existing systems, while the 650-nm side pointed out that only one firm is making the 635-nm laser diodes, practically speaking, and claimed that this is expensive and makes it difficult to develop consumer products
In addition, 650-nm group explained that developing higher-output 650-nm device would make future higher recording speed possible. The DVD Forum decided to split the DVD-R standard into two parts, one for authoring and one for general use. The authoring standard maintains compatibility with existing systems, using a 635-nm source. The general-use standard uses the 650-nm light source, making it easier to achieve lower product cost and provide additional DVD-R capabilities for DVD-RAM and DVD-RW drives.
In other words, compatibility has been deliberately lost between the two. Addressing and schemes to prevent unauthorized copying will also be different. |
