DVD-R DL
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DVD-R DL (DL stands for Dual Layer[1]), also called DVD-R9, is a derivative of the DVD-R format standard. DVD-R DL discs hold 8.54 GB (7.96 GiB) per side by utilizing two recordable dye layers, each capable of storing nearly the 4.7 GB (4.38 GiB) of a single layer disc -almost doubling the total disc capacity. Discs can be read in many DVD devices (older units are less compatible) and can only be written using DVD-R DL compatible recorders.
| DVD-R DL | Capacity | |
|---|---|---|
| Physical size | GB | GiB |
| 12 cm, single sided | 8.5 | 7.92 |
| 12 cm, double sided | 17.1 | 15.93 |
| 8 cm, single sided | 2.6 | 2.42 |
| 8 cm, double sided | 5.2 | 4.84 |
DVD-R DL has compatibility issues with legacy DVD-ROM drives known as pickup head overrun. To avoid this issue, the two layers of the disc need to be equally recorded. But this is a contradiction with the sequential nature of the DVD recording. Thus DVD Forum under Pioneer's lead developed a technology known as Layer Jump Recording (LJR), which incrementally record smaller sections of each layer to maintain compatibility with DVD-ROM drives.
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[edit] 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).[2]
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.[3] 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.[2] 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. However only blank disks and drives that support the latter mode are currently available.
[edit] 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.
| Disk Type | number of sectors for data (2,048B each) | capacity in bytes | capacity in GB | capacity in GiB |
|---|---|---|---|---|
| DVD-R (SL) | 2,298,496 | 4,707,319,808 | 4.7 | 4.384 |
| DVD+R (SL) | 2,295,104 | 4,700,372,992 | 4.7 | 4.378 |
| DVD-R DL | 4,171,712 | 8,543,666,176 | 8.5 | 7.957 |
| DVD+R DL | 4,173,824 | 8,547,991,552 | 8.5 | 7.961 |
[edit] See also
[edit] References
- ^ "Standard ECMA-382 120 mm (8,54 Gbytes per side) and 80 mm (2,66 Gbytes per side) DVD Recordable Disk for Dual Layer (DVD-R for DL)". ecma-international.org. http://www.ecma-international.org/publications/standards/Ecma-382.htm. Retrieved 2008-10-29.
- ^ a b Robert DeMoulin. "Understanding Dual Layer DVD Recording". BurnWorld.com. http://www.burnworld.com/howto/articles/intro-to-dual-layer.htm. Retrieved 2007-07-06.
- ^ "DVD players benchmark". hometheaterhifi.com. 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). Retrieved 2008-04-01.
[edit] External links
- DVD-R9 and DVD+R9 Hardware, Technologies and Standards by The DVD Insider
