DVD-RW DL

DVD-RW DL is a rewritable optical disc standard with storage capacity of 8.5 GB. DVD-RW DL discs employ two rewritable dye layers. It's approved by DVD Forum as "DVD Specifications for Re-recordable Disc for Dual Layer (DVD-RW for DL) Physical Specifications, Version 2.0".

Dual layer recording

Dual Layer recording allows DVD-R and DVD+R discs to store significantly more data, up to 8.5 gigabytes per side, per disc, compared with 4.7 gigabytes for single-layer discs. DVD-R DL was developed for the DVD Forum by Pioneer Corporation, DVD+R DL was developed for the DVD+RW Alliance by Philips and Mitsubishi Kagaku Media (MKM).cite web|url=http://www.burnworld.com/howto/articles/intro-to-dual-layer.htm|title=Understanding Dual Layer DVD Recording |publisher=BurnWorld.com |author=Robert DeMoulin |accessdate=2007-07-06]

A Dual Layer disc differs from its usual DVD counterpart by employing a second physical layer within the disc itself. The drive with Dual Layer capability accesses the second layer by shining the laser through the first semi-transparent layer. The layer change can exhibit a noticeable pause in some DVD players, up to several seconds. [cite web|url=http://www.hometheaterhifi.com/cgi-bin/shootout.cgi?function=search&articles=all&type=&manufacturer=0&maxprice=0&deInt=0&mpeg=0#SamsungBD-P1000%20Blu-ray/DVD%20Player%20(HDMI)|title=DVD players benchmark|publisher=hometheaterhifi.com |accessdate=2008-04-01] This caused more than a few viewers to worry that their dual layer discs were damaged or defective, with the end result that studios began listing a standard message explaining the dual layer pausing effect on all dual layer disc packaging.

DVD recordable discs supporting this technology are backward compatible with some existing DVD players and DVD-ROM drives. Many current DVD recorders support dual-layer technology, and the price is now comparable to that of single-layer drives, though the blank media remains more expensive. The recording speeds reached by dual-layer media are still well below those of single-layer media.

There are two modes for dual layer orientation. With "parallel track path" (PTP), used on DVD-ROM, both layers start at the inside diameter (ID) and end at the outside diameter (OD) with the lead-out. With "opposite track path" (OTP), used on DVD-Video, the lower layer starts at the ID and the upper layer starts at the OD, where the other layer ends, they share one lead-in and one lead-out. [ [http://www.discusa.com/Website/Pages/Products%20and%20Technology/DVD%20Basics/dvdbasicsdiscformat.htm Disc USA *Link appears broken as of May 21, 2008] ]

ee also

*DVD+RW DL

References

External links

* [http://www.dvdforum.org/35scmtg-resolution.htm]