Philips demonstrated double layer DVD recording as well as 16x DVD recording
for DVD+R. Double layer DVD+R technology has been jointly developed by Philips
and Mitsubishi Kagaku Media (MKM), doubling the data capacity of recordable
DVD to 8.5GB.
The companies had to overcome significant technological challenges for recording
on to two layers. Development of the appropriate double layer organic media
(MKM), the logical formatting as well as the hardware implementation of the
technology were issues to be faced.
One challenge to overcome was to minimize the interference between data
recorded in the first layer while recording on the second layer. In addition,
the first layer requires the use of a transparent thin metal layer that will
allow the light beam to penetrate onto the second layer without affecting
the first layer. Towards this direction, MKM developed new materials used
for the spacer layer, the transparent metal reflector.
According to the standard, reflection back off any layer must be above 18%
to ensure proper operation, especially in the case of defective media where
the surface may have fingerprints for example and the signal must be strong
enough to overcome losses caused by any defects. This also applies to dual
where part of the signal destined for the second layer is absorbed by the
top layer. Here, Philips has managed to achieve 50% reflection, well above
the 18% minimum.
Another issue with dual layer media is the addressing strategy which must
be implemented. When writing on a dual layer disc, logically the entire 8.5Gbytes
appears as one contiguous stream. Physically this is not the case however,
and this poses a problem when part of the disc is left unrecorded. Any part
been recorded on, must be "de-iced", ie filled with dummy data, which is
similar to formatting a hard disk for example.
The reason for this has to do with
compatitbilty. For example, take a disc on which the entire first layer
and part of the second layer have been written on. When this disc is then
read, and a seek on the first layer to some point further ahead is requested
which will move forward to a point on the second layer, there are
methods the reading drive can adopt (the standard itself does not define
what the behaviour in such a situation should be). The first is to seek forward
until it reaches the
the first layer, switch to the second layer (OTP), continue seeking forwards
until it reaches the desired point.
The second method is to simply jump from
layer, at the point from which the request is made, directly onto the same
position on the second layer and back up until it reaches the desired position.
If the point at which the switch from the first layer to the second
layer is made, the second layer has not been "de-iced", the reading drive
will not be able to determine its position since there is no address information
available on the unwritten portion of the disc. Hence, de-icing the unwritten
parts of the disc simply allows a drive using this approach to navigate the
entire drive without "getting lost".
Philips uses a single laser diode for recording on the two layers. Recording
is done at 2.4x for both layers, since higher speeds would require more power.
Currently, the laser power for recording at 2.4x has been kept lower than
30mW for both layers. So the drive only adjusts the laser focusing point
in order to record on the first or the second layer. In addition, the
data-to-clock jitter is less than 9.0% for both layers.
The first Philips drive to support double layer is the DVDRW885. The drive
support 8x writing for DVD+R (4.7GB) Z-CLV, 2.4x CLV for DVD+R9 (8.5GB),
4x for DVD-R, 2x for DVD-RW, 4x for DVD+RW, 24x CD-R and 10x CD-RW.In the
reading part, the supported speeds are 12x on DVD-ROM, 7x on DVD+R DL, 7x
DVD-R, 7x on DVD-RW, 40x on CD-R, 32x on CD-RW. Of course, the drive uses
a different laser diode for CD recording/reading. Availability on the market
is expected by May.
We witnessed a demonstration of a dvd video compilation written
onto double layer media which took a little over 39 minutes (7.034 GBytes).
The recorded disc was then played on a standard dvd player for confirmation,
where both layers were
read without problems.
Below you can see the NeroCDSpeed reading graph of th erecorded DVD+R9 disc:
- Operating System Windows 2000
- Drive PHILIPS DVD8421
- Firmware Version 2L27
- Serial Number BASE_PLUS_040227
- Disc DVD+R DL
- Capacity 5.31 GB
The first Philips 16x DVD+RW burner is the DVDR1640, to be available by
June. The drive records at 16x CAV on DVD+R media, and also
is capable of DVD+R9 writing. The basic features include the Dynamic Calibration
to ensure writing quality at high DVD speeds, the Seamless Link technology
and and the Optimum recording speed feature that selects the appropriate
writing speed for any recordable disc. The detailed specifications of the
new drive are available below:
- 8.5 GB storage capacity
- Access time (typical) 120ms on CD, 140ms on DVD
- Disc capacity 8.5 GB DVD+R
DL, 4.7 GB DVD+R
- Recording format UDF and ISO 9660
- Recording media 8cm CDs (only in hor.
pos.), CD-R, CD-RW, DVD+R, DVD+R double layer,
DVD+RW, DVD-R, DVD-RW
- Supported formats 8cm discs, CD-Audio, CD-Bridge,
CD-Extra, CD-I, CD-Recordable, CD-Rewritable, CD-ROM, CD-Text, DVD+R, DVD+RW,
DVD-ROM, DVD/R, DVD/RW, Photo CD
- Write modes Disc at once (DAO), Fixed packet, Multi
Session (MS), Over-burn writing, Packet writing, Raw mode burning, Session
at once (SAO), Track at once (TAO),Variable packet
- Reading speeds 16x on
DVD-ROM, 10x on DVD+R DL, 10x on DVD+R, 10x on DVD+RW, 10x on DVD-R, 10x
on DVD-RW, 40x on CD-R, 32x on CD-RW
- Recording speeds 16x on DVD+R, 2.4x
on DVD+R DL, 8x on DVD-R, 40x CD
- Rewriting speeds 4x on DVD+RW, 4x on
DVD-RW, 24x CD-RW
Philips Nexperia reference kit