|
|
|
|
| Optical media types |
- Laserdisc (LD), Video Single Disc (VSD)
- Compact Disc (CD): Red Book, 5.1 Music Disc, SACD, PhotoCD, CD-R, CD-ROM, CD-RW, CD Video (CDV), Video CD (VCD), SVCD, CD+G, CD-Text, CD-ROM XA, CD-i
- MiniDisc (MD) (Hi-MD)
- DVD: DVD-R, DVD+R, DVD-R DL, DVD+R DL, DVD-RW, DVD+RW, DVD-RW DL, DVD+RW DL, DVD-RAM, DVD-D
- Ultra Density Optical (UDO)
- Universal Media Disc (UMD)
- HD DVD: HD DVD-R, HD DVD-RW, HD DVD-RAM, HD DVD-ROM
- Blu-ray Disc (BD): BD-R, BD-RE
|
|
| Standards |
|
|
| Further reading |
|
|
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).[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 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. 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.[3]
See also
External links
|
