DVD+R DL

A single DVD+R DL disc

DVD+R DL (DL stands for Double Layer) also called DVD+R9, is a derivative of the DVD+R format created by the DVD+RW Alliance. Its use was first demonstrated in October 2003. DVD+R DL discs employ two recordable dye layers, each capable of storing nearly the 4.7 GB capacity of a single-layer disc, almost doubling the total disc capacity to 8.55 GB (or 7.96 GiB). Discs can be read in many DVD devices (older units are less compatible) and can only be created using DVD+R DL and Super Multi drives. DL drives started appearing on the market during mid 2004, at prices comparable to those of existing single-layer drives. However, the current price of DL media is up to twice as expensive as that of single-layer media. The latest DL drives write double layer discs at a slower rate (up to 10×) than current single-layer media (up to 16×).

A double layer rewritable version called DVD+RW DL has been released but is expected to be incompatible with existing DVD devices.

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).^[1]

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.^[2] This caused more than just 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.^[1] 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, parallel track path (PTP) and Opposite Track Path (OTP). In PTP mode, used for DVD-ROM, both layers start recording at the inside diameter (ID) with the lead-in and end at the outside diameter (OD) with the lead-out. Sectors are sequenced from the beginning of the first layer to the end of the first layer, then the beginning of the second layer to the end of the second layer. In OTP mode, used for DVD-Video, the disk is recorded in the same physical way, but the sectors are sequenced from the beginning of the first layer to the end of the first layer, then the end of the second layer to the beginning of the second layer. In both modes, the layers share one lead-in and one lead-out.^{[citation needed]}

Recordable DVD capacity comparison

For comparison, the table below shows storage capacities of the four most common DVD recordable media, excluding DVD-RAM. (SL) stands for standard single-layer discs, while DL denotes the dual-layer variants. See articles on the formats in question for information on compatibility issues.

See also

• Book type
• DVD
• DVD+R
• DVD+RW DL

References

• Bennett, Hugh. Understanding Recordable & Rewritable DVD. Cupertino: Optical Storage Technology Association, Apr. 2004.
• Bennett, Hugh. "DVD±RW DL—D.O.A.?" EMedia Xtra May 10, 2005.

External links

• Double-layer DVD heats up standards battle - ZDNet UK
• JVC's April 2005 announcement on DVD+RW DL
• DVD-R9 and DVD+R9 Hardware, Technologies and Standards by The DVD Insider