With the finalization of the Basic Format Specifications for the Dual
Layer DVD+RW discs, the first media should be expected later this
The DVD+RW Alliance announced the establishment of the "DVD+RW DL"
format almost two years ago. Philips released the DVD+RW part 2: Dual
Layer, volume 1; DVD+RW 8.5 Gbytes, Basic Format Specifications,
version 1.0, earlier this month.
The recording speed for DVD+RW DL recording is not expected to reach
the current speed available for single layer DVD+R, due to the high
power requirements for dual layer recording. The 2.4x is the debut
speed for dual recording, expected to reach 4X in one year. Initial
media will be write-once, while 8cm discs are also included in the
specifications, offering 2.66GB available space per layer.
The DVD+RW DL media use two phase-change layers. The first
semi-transparent layer should be formed in a way that it would balance
transparency characteristics with efficient laser beam absorption
just like it is the case with single layer recordable DVDs.
High transparency could be achieved by using a thinner recording
layer, but this would result in a drop of laser absorption, which is
insufficient to form and erase marks (recording signal patterns).
In addition, to maintain compatibility with current DVD players, the
discs should feature a reflectivity of minimum 18%, a value
technically difficult to achieve. Thus, the DVD+RW DL discs will
possibly feature a lower reflectivity. In that case, a firmware
upgrade in the existing DVD players/writers would be essential to
The first DVD+RW DL media are expected to appear in the market later
this year, although Philips has not made any official announcement
Japanese JVC has also announced it has made progress in developing
double layer DVD-RW media. The DVD-RW DL format was approved by the
DVD Forum last February.