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{{Optical disc authoring}}
{{Missing information|dates|date=August 2020}}
{{short description|DVD Recordable Dual Layer}}

'''DVD-R DL''' (DL stands for '''Dual Layer'''<ref name="ECMA international Standard 382">{{cite web|url=http://www.ecma-international.org/publications/standards/Ecma-382.htm|title=Standard ECMA-382 120 mm (8.5GB per side) and 80 mm (2,66 G DVD Recordable Disk for Dual Layer (DVD-R for DL) |publisher=ecma-international.org |access-date=2008-10-29}}</ref>), also called '''DVD-R9''', is a derivative of the [[DVD-R]] format standard. DVD-R DL discs hold 8.5 GB by utilizing two recordable dye layers, each capable of storing a little less than the 4.7 [[gigabyte]] (GB) of a single layer disc, almost doubling the total disc capacity.<ref>{{Cite news |title=Dual-Layer DVD explained. |newspaper=Insync |date=March 2004 |url=https://www.sweetwater.com/insync/dual-layer-dvd-explained/ |author1=Sweetwater }}</ref> Discs can be read in many DVD devices (older units are less compatible) and can only be written using DVD-R DL compatible recorders. It is part of [[optical disc recording technologies]] for [[digital recording]] to [[optical disc]].

DVD-R DL products started appearing on the market during mid-2004.{{Citation needed|date=September 2024}}

== Capacities ==
{| class="wikitable" style="text-align:center;"
!''DVD-R DL''
!colspan="2"| Capacity
|-
! Physical size || Nominal capacity in GB (109 bytes) || Typical capacity in GiB (230 bytes)
|-
|style="text-align:left;"| 12 cm, single sided || 8.5 || 7.96
|-
|style="text-align:left;"| 12 cm, double sided || 17.1 || 15.91
|-
|style="text-align:left;"| [[MiniDVD|8 cm]], single sided || 2.6 ~ 2.7 || 2.47
|-
|style="text-align:left;"| [[MiniDVD|8 cm]], double sided || 5.3 || 4.94
|}

<ref>{{Cite web|last=Marshall|first=Dave|date=2001-10-04|title=Sizes and capacities of DVD|url=https://users.cs.cf.ac.uk/Dave.Marshall/Multimedia/node135.html|access-date=2020-07-21|website=users.cs.cf.ac.uk}}</ref>
=== Compatibility ===
{{See also|DVD_recordable#Adaption}}
DVD-R DL has compatibility issues with legacy DVD-ROM drives known as [[pickup head]] [[Buffer overflow|overrun]].{{elaborate|date=July 2020}} 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|Layer Jump Recording (LJR)]], which incrementally record smaller sections of each layer to maintain compatibility with DVD-ROM drives.

According to the developer of [[dvd+rw-tools]], DVD-R DL lacks appendable writing support in the "incremental" recording mode that is normally used for multisession writing on single-layer media, and requires the use of the more complicated "Layer Jump Recording", so multi-session writing is not possible without technical difficulty. Without appendable writing, any space not used during the first write is wasted.<ref>[https://fy.chalmers.se/~appro/linux/DVD+RW/-RW/#nomultisess DVD-R[W] for Linux] "In addition DVD-R Single Layer Incremental strategy provides for multiple sessions and dvd+rw-tools do utilize it." "In other words Dual Layer Incremental recordings do not have notion of multiple sessions and come out unconditionally unappendable, just like DAO. If multisessioning is a requirement, then Layer Jump is the only option."</ref>

DVD-R DL media has been discontinued by most manufacturers. [[DVD+R DL]] is dominating the market for dual layered media.{{Citation needed|date=September 2024}}

== Dual layer recording ==
Dual Layer recording allows [[DVD-R]] and [[DVD+R]] discs to store significantly more data, up to 8.5 GB, per disc, compared with 4.7 GB for single-layer discs. DVD-R DL was developed for the DVD Forum by [[Pioneer Corporation]], [[DVD+R DL]] (formally known as Double Layer) was developed for the DVD+RW Alliance by [[Philips]] and Mitsubishi Kagaku Media (MKM).<ref name="Dual-layer-BurnWorld">{{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 |access-date=2007-07-06 |archive-date=2010-04-21 |archive-url=https://web.archive.org/web/20100421150137/http://www.burnworld.com/howto/articles/intro-to-dual-layer.htm |url-status=dead }}</ref>

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 player]]s, up to several seconds.<ref>{{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 |access-date=2008-04-01 |url-status=dead |archive-url=https://web.archive.org/web/20080313232626/http://www.hometheaterhifi.com/cgi-bin/shootout.cgi?function=search&articles=all&type=&manufacturer=0&maxprice=0&deInt=0&mpeg=0 |archive-date=March 13, 2008 }}</ref> 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.

The stacked, shine-through arrangement of layers does come with a small increase in error rate due to reduced reflectivity of the written layers, and a similar small risk of crosstalk interference. One of the techniques employed to help compensate for these reliability shortcomings is a 10% increase in minimum mark (digital 0 or 1) length on the disc, with a corresponding 10% increase in rotation speed and 10% reduction in gross recordable capacity, accounting for the lower capacity of a single-sided dual-layer DVD at 8.5 billion bytes, versus a double-sized, single-layer DVD at 9.4 billion (for 12 cm discs). Detail differences in formatting and file structure mean the "usable" data area capacity does not change by exactly this much, but for all intents a DVD-R DL has effectively 20/11ths the capacity of a DVD-R SL, and the same holds for +R, commercially pressed, and 8 cm discs.

DVD recordable discs supporting this technology are backward compatible with some existing DVD players and [[DVD-ROM]] drives.<ref name="Dual-layer-BurnWorld"/> 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 first layer ends. The two layers share one lead-in and one lead-out. Only blank disks and drives that support the latter mode are currently available. 

== 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.

{| class="wikitable" style="text-align:center;"
|-
! Disk Type || number of sectors for data (2,048 B each)|| capacity in bytes || nominal capacity in GB (109 bytes)
|-
|style="text-align:right;"| DVD-R (SL) || 2,298,496 || 4,707,319,808 || 4.7
|-
|style="text-align:right;"| DVD+R (SL) || 2,295,104 || 4,700,372,992 || 4.7
|- style="background:gray; color:white"
|style="text-align:right;"| DVD-R DL || 4,171,712 || 8,543,666,176 || 8.5
|-
|style="text-align:right;"| DVD+R DL || 4,173,824 || 8,547,991,552 || 8.5
|}

== See also ==
* [[DVD+R DL]]
* [[DVD]]
* [[DVD-R]]
* [[DVD-RW]]
* [[DVD-RW DL]]
* [[Book type]]
* [[MultiLevel Recording]]
* [[List of optical disc manufacturers]]

==References==
{{Reflist}}

==External links==
* [http://www.audioholics.com/news/editorials/DVDInsider-DVDR9.php DVD-R9 and DVD+R9 Hardware, Technologies and Standards] by The DVD Insider

{{DEFAULTSORT:Dvd-R Dl}}
[[Category:DVD]]
[[Category:Optical computer storage]]
[[Category:Optical computer storage media]]

DVD-R DL - Revision history

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