Disc bd after this visibly different characteristic

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Disc (BD), after this visibly different characteristic. Blu-ray technology further increases the storage capacity of optical media without changing the form factor. On a 12-cm disc, similar to those used for CD-ROMs and DVD-ROMs, BD derives a 25 GB storage capacity from the basic disc. When you add a second layer to the same or opposite side of the disc, you attain 50 GB of storage. The Blu-ray laser is of a shorter wavelength (405 nm) than that of DVD (650 nm) and CD (780 nm) technologies. As a result, and through the use of refined optics, the laser can be focused on a much smaller area of the disc. This leads to a higher density of information being stored in the same area.
An interesting point to note is that designers of the Blu-ray technology do not have to stop with the common double-layer solution to increase capacity. Blu- ray Discs with more than four layers on a side have been demonstrated, largely owing to the extremely accurate focus attainable with the Blu-ray laser. In the interest of completeness, it should be mentioned that a high-definition technology directly related to DVD, called HD DVD, was once a competitor to Blu-ray. In February 2008, Toshiba, HD DVD’s primary champion, gave up the fight, conceding to Blu-ray Disc as the winner in the high-definition optical-disc race. HD DVD featured red- and blue-laser compatibility and 15 GB data storage capacity. Table 2.2 draws together the most popular optical-disc formats and lists their respective capacities. Some of these formats have already been introduced; others are presented in the upcoming section “Recordable Discs and Burners.” Boldfaced capacities in the table are the commonly accepted values for their respective formats. Table 2.2: Optical discs and their capacities Disc Format Capacity CD SS (includes recordable versions) 650 MB, 700 MB , 800 MB, 900 MB DVD-R/RW SS, SL 4.71 GB ( 4.7 GB ) DVD+R/RW SS, SL 4.70 GB ( 4.7 GB ) DVD-R, DVD+R DS, SL 9.4 GB DVD-R SS, DL 8.54 GB ( 8.5 GB ) DVD+R SS, DL 8.55 GB ( 8.5 GB ) DVD+R DS, DL 17.1 GB BD-R/RE SS, SL 25 GB BD-R/RE SS, DL 50 GB
Table 2.2: Optical discs and their capacities Disc Format Capacity BD-R/RE DS, DL 100 GB SS = single-sided; DS = double-sided; SL = single-layer; DL = dual-layer Optical Drive Data Rates CD-ROM drives are rated in terms of their data transfer speed. The first CD- ROM drives transferred data at the same speed as home audio CD players, 150 KBps, referred to as 1X. Soon after, CD drives rated as 2X drives that would transfer data at 300 KBps appeared. They increased the spin speed in order to increase the data transfer rate. This system of ratings continued up until the 8X speed was reached. At that point, the CDs were spinning so fast that there was a danger of them flying apart inside the drive. So, although future CD drives used the same rating (as in 16X, 32X, and so on), their rating was expressed in terms of theoretical maximum transfer rate; 52X is widely regarded as the highest multiplier for data CDs. Therefore, the drive isn’t necessarily spinning faster, but through electronics and buffering advances, the transfer rates continued to increase.

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