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DVD+ReWritable technology
DVD+ReW ritable
Ho w it works
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DVD+ReWritable technology
D VD+ReWritab le and ho w it works
Introduction
Arising from the need to store ev er -larger amounts of data on an optical disc,the pre-recorded D VD-Video
(Digital V ersatile Disc) can store 4.7 gigab yte of information corresponding to mor e than two hours of highquality digital video on a single-sided (CD-size) 12 cm disc.The high-density successor to the popular CD media
family ,DVD not only meets f oreseeable capacity needs,it is also well-suited to the operating needs of the latest
multimedia PCs and CE appliances using digitized audio,graphical and video information.
Though pre-recorded D VDs (D VD-R OM and D VD-Video discs) ha ve been around f or a while,recordable and
rewritable D VDs are a mor e recent but crucial dev elopment.Already ,several re writable formats exist:
DVD+RW ,D VD-R W and D VD-RAM.Of these,DVD+R W,developed in co-operation by He wlett-Packard,
Mitsubishi Chemical,Philips,Ricoh,Sony and Yamaha,provides a breakthrough in D VD technology:it is the only
rewritable format that pr ovides full compatibility with existing D VD-Video play ers and D VD-R OM drives.
As consumer and IT applications for D VD continue to converge,DVD+RW provides a disc format suitable for
both real-time video recording and random data r ecording – the best of both worlds – in a system that also
offers effective means to pre vent unauthorized cop ying of copyright-pr otected content.
D VD+R W:Physical format
DVD+R W is designed to be used for both data and video content acr oss PC and entertainment applications.
DVD+R W r ecognizes that these applications are rapidly conv erging,and that content must be portable across
various types of equipment.DVD+R W has theref ore been designed to be compatible with existing D VD-ROM and
DVD-Video formats.
An important benefit for PC applications is the capability of the DVD+RW format to allow ‘CA V r ecording’
(Constant Angular V elocity).Due to the constant rotation speed of the disc CAV r ecording allows for fast
random access.Yet two other benefits are the incorporation of ‘Defect management’,especially designed for
reliability of the data,and ‘Quick formatting’,enabling instant use of blank discs. Above-mentioned benefits
support the use of the format in data systems requiring high performance.For video applications the format has
the capability of ‘lossless linking’ allowing to use variable bit rate r ecording for longer pla ying times.
DVD+R W at a glance
- Single-sided disc with 4.7 GB capacity
- Double-sided disc with 9.4 GB capacity
- Uses a bare disc - no cartridge required
- 650 nm laser (numerical aperture 0.65)
- Constant linear data density
- CL V and CA V recor ding
-Write speeds from 1x to 2.4x D VD-Video data rates
- Defect management handled by the drive
- Quick formatting
- Uses same 8-16 Modulation and RS code as DVD-ROM
- Recording
- Sequential and random recording
- 32 kB ERCO blocks
- Lossless linking
- Address information:
- Spiral groove with radial wobble (32T period)
- Phase modulation addresses
- Four addresses per ECC block of 32 kB
After recording all ph ysical parameters comply with the D VD-R OM specification.
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DVD+RW Video format
The pre-recorded D VD-Video mark et is booming,and Philips believes that D VD-Video will become the
mainstream pre-recor ded video distribution format.Adding recording capabilities to D VD pla yers will further
boost the appeal of the DVD system.Of course,for long-term success it is essential that both home-recorded
and pre-recorded discs can be pla yed on the same equipment.This is one r eason why D VD+RW is a major
breakthrough in re writable D VD technology .
Philips’ DVD+ReWritable Video format,based on the recently announced 4.7 GB DVD+R W storage technology ,
provides compatibility with existing D VD-Video and D VD-R OM equipment,and allows media interchange
between consumer electronic equipment and PC platforms.Moreov er ,DVD+R W offers the possibility to
combine digital video and digital data in a single file system as required for multimedia r ecording applications.
T wo-way compatibility
DVD+RW Video technology provides a unique advantage:Recorded discs can be played back on existing D VDVideo players.
Recordings made with a DVD Video Recorder on DVD+RW discs can be played on D VD Video players as well as
on PCs with a DVD-R OM driv e and MPEG2 video decoding capability .D VD+R W discs offer up to 4 hours
record/pla yback time per side,resulting in recording capacities of up to 8 hours for double-sided discs.
High-quality video at extended recording times
DVD+RW Video is encoded in MPEG2 with variable bit-rate,providing high bit-rates where necessary while no
storage capacity is wasted in scenes with less dynamic video.This means that with the same disc capacity much
longer recording times can be achiev ed,or the recording quality can be further improved without r educing the
recording time.DVD-Video pla yback compatibility with real-time variable bit-rate recor ding is achieved by using
‘Lossless linking’,a technique developed specifically for D VD+R W.
Simplified editing
Philips’ DVD+RW Video technology also offers easy-to-use editing facilities.Whereas editing private camcorder
material on conventional equipment generally requir es two video devices,random access to a DVD+R W disc
means editing can be done using a single DVD Video Recorder .This brings editing within reach of the a verage
consumer and makes it quick and very easy to use.Because of its PC-compatibility,advanced editing of
DVD+RW Video can be done on a PC.
With the addition of DVD+RW to the DVD media family,consumers get the best of both worlds – pre-recorded
high-quality recordings,plus home-recording capability.Without doubt,rewritable DVD will stimulate further
growth of the D VD Video market,strengthening its long-term interest to both equipment manufacturers and the
movie industry alike.
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DVD+ReWritable technology
D VD+ReWritab le and ho w it works
D VD+R W:PC applications and file handling
With the growing trend towar ds multimedia documents,which require large amounts of disc space,DVD+RW
offers the ability to easily create,share,store and access such content-rich documents using a single disc.
In DVD+R W,data is arranged on a disc according to the industry-standard UDF (Universal Disc Format)
standardized and published by OST A (Optical Storage T echnology Association).UDF is well suited to handling file
changes and (random) writing of small amounts of data,and facilitates the design of multi-platform applications.
Today ,UDF is increasingly used for writing to CD-RW discs instead of the less flexible ISO9660 file system f ormat
that was developed to handle read-only data a pplications.Virtually platform-independent,UDF makes D VD
systems highly compatible with CD-based data systems.Also,being designed to handle the massive capacities of
future optical storage systems,UDF provides excellent forward compatibility.
D VD+R W:Phase-change technology
In its original state,the recording layer of a D VD+R W disc is polycrystalline.During writing,a focused laser beam
selectively heats areas of the phase-change material abov e the melting temperature (500-700°C),so all the atoms
in this area can move rapidl y in the liquid state.Then,if cooled sufficiently quickly ,the random liquid state is
‘frozen-in’ and the so-called amorphous state is obtained (see Fig.1).If the phase-change layer is heated below the
melting temperature but above the crystallization temperature (200°C) for a sufficient time (at least longer than
the minimum crystallization time),the atoms revert back to an ordered state,i.e.the crystalline state.
The amorphous and crystalline states have different r efractive indexes,and can therefore be optically
distinguished.In the DVD+R W system,the amorphous state has a lower r eflectance than the crystalline state and,
during read-out,this produces a signal identical to that of a regular dual la yer D VD-R OM disc,making it possible to
read D VD+R W discs on D VD-R OM drives and D VD Video players.
The phase-change medium consists of a grooved polycarbonate substrate onto which a stack (usuall y four lay ers)
is sputtered (see Fig.2).The phase-change (recording) la yer is sandwiched between dielectric la yers.A commonly
used phase-change material is Ag-In-Sb-Te alloy. The chemical composition of the phase-change lay er determines
the minimum time of crystallization.The disc structure (lay er thickness,thermal capacities and thermal
conductivity) determines the cooling rate during writing.Precise control of the recording-la yer composition is
important to obtain the desired recording properties.In general,low recording pow ers are achieved b y using thin
layers. The lay er thickness and refractive index es determine the optical properties of the phase-change medium.
The phase-change medium can be rewritten in a single pass of the focused laser beam;this is sometimes referr ed
to as ‘direct o verwriting’.In the DVD+RW system,the data is recorded on discs by means of a write strategy,using
different laser output levels (see Fig.3).This strategy (see Fig.4a) has two parts:
a pulsed part (pulsing is necessary to write amorphous ‘marks’),and
•
a non-pulsed part,in which the strategy writes crystalline areas between the marks.
•
The write strategy therefore writes new data to the disc while simultaneously o verwriting old data.Moreover,
DVD+R W supports CLV (see Fig.4a) as well as CAV (see Fig.4b).This process can be r epeated several thousand
times.
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Label
Polycarbonate
2P resin
Reflective layer
Upper dielectric layer
Recording layer (Ag-In-Sb-Te)
Lower dielectric layer
Polycarbonated disc substrate
Laser beam
Groove
Single sided disc
(Not to scale)
Creating amorphous regions
temp
~600 C
Creating polycrystalline regions
melting point
time
tcrystal tcrystal
tpass
tcooling
crystallisation
temperature
temp
melting point
time
crystallisation
temperature
o
~200 C
o
~600 C
o
~200 C
o
Figure 1.
Figure 2.
Fig.2.Section through a single-sided 4-layer D VD+R W disc (4.7 GB).
By exposure to the heat from a laser,the recording layer can be changed fr om a polycrystalline (more reflectiv e)
state to an amorphous (less reflective) state,and vice versa.The lay ers are deposited onto a polycarbonate
substrate;the latter molded with a spiral groove for servo guidance,address information and other data.
DVD+RW discs are supplied ready-for -use in the polycrystalline state.They can be written at between 1x and
2.4x DVD-Video data rates,i.e.11-26 Mbit/s,allowing CA V operation (Constant Angular V elocity).
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DVD+ReWritable technology
P
laser output (mW)
P
bias
P
erase
P
write
optical powers at the
entrance surface of the disc
15
8
3
0.7
0.1
T
top
T
mp
2.4 x
T
ch
1 x
T
ch
T
top
T
mp
P
bias
P
erase
P
for 3T mark
(forms an amorphous
region on the disc)
for no mark
(forms a polycrystalline
region on the disc)
write
D VD+ReWritab le and ho w it works
Figure 3
Figure 4a
Fig.3.During recording,the laser output is modulated using
three power lev els;P
write,Perase
and P
,according to a
bias
predefined write strategy .The laser in a D VD+R W system has
to be pulsed (for thermal reasons) to form well-defined
amorphous regions of the desired length (see Fig.1).The power
level P
amorphous marks.The optimum recording pow ers (P
P
erase
is used to form the crystalline regions between
erase
and P
) depend on the disc,the recorder and the
bias
write
,
recording speed.Their values for individual disc/recor der
combinations and different recording speeds ar e determined
by the Optimum Pow er Control (OPC) pr ocedure.
Fig.4a.Write strategy example.Shown here are the laser
modulation strategy to record the shortest ‘pit’ defined in the
DVD system,the ‘3T mark’,and the strategy to record ’no
mark’.Recording a mark means creating a low-reflectivity
(amorphous) region in the active la yer;recording no mark
means creating a high-reflectivity (polycrystalline) region as
illustrated in the graphs.
Figure 4b
6
modulated power
constant power
Note that new data is simply written over existing data in a
single pass.DVD+R W is theref ore known as a Direct
Overwrite (DOW) system.
Fig.4b.Write strategy principle for CAV operation
For good signal quality at both the 1x and the 2.4x speed,the
pulse duration for the write pulses (T
and Tmp) is kept (more
top
or less) constant over the velocity range.Of course,the
channel bit duration (Tch) changes with velocity .
This write strategy prevents the recrystallization of the
amorphous mark that has just been written.Using this write
strategy the disc can be written in CAV mode,but also at any
desired CL V v elocity between 1x and 2.4x.
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D VD+R W:Lossless linking
In the DVD+RW Video format,video can be encoded with a variable bit-rate (VBR).Because the writing process
takes place at a constant bit rate,the writing process needs to be suspended and continued frequently.Normally,
this would result in a linking loss,making the disc incompatible with read-only devices lik e D VD Video players and
DVD-R OM driv es.With D VD+R W it is possible to perform lossless linking,i.e.to suspend and continue the
writing process without linking loss.This feature mak es the format very efficient and suitable for random write in
data as well as video applications.Additionally ,lossless linking makes it possible to r eplace any individual 32 kB
block (recording unit) by a new one,without losing compatibility .
For lossless linking it is necessary to write any data block in the correct position with high accuracy (within
1 micron).For this purpose the groov e is mastered with a high wobble fr equency (817 kHz at n=1),which
ensures that the writing can be started and stopped at an accurately defined position.The writing clock as
obtained from this groov e is very accurate.At the same time,address information is stored in this w obbled
groove by locall y inverting the sign of the wobbled wa veform.For each ERCO block,which is 32 kB,four
addresses exist,resulting in a reliable addr ess format with large detection margins.
D VD+R W:Disc manufacturing
DVD+RW discs are manufactured using equipment similar to that already found in con ventional D VD factories,
but some dedicated equipment is needed.For instance,the active layer formed by sputtering is amorphous,and
has to be converted to the polycrystalline phase by heating it with a high DC power.This process,called
initialization,ensures that every new disc reaching users is in the high-reflectance phase.The additional
investment needed for manufacturing D VD+RW discs is lower than what would be required f or other
rewritable D VD technologies.
D VD+R W:Tw o-way compatibility with existing DVD drives
An important feature of the DVD+RW disc is its compatibility with existing DVD-Video and D VD-R OM drives.
All physical parameters fit within the D VD-R OM specification.The reflectivity is in the same range as the duallayer r eflectivity specification of a read-only disc and the density is the same as for the single la y er specification.
The main parameters are summarized in T able 1.The choice of identical parameters optimizes pla yability in
current read-only pla yers.
Table 1.
DVD+RW
compared with
DVD-R OM
Media type Phase change Read-only Read-only
User data capacity 4.7 GB 4.7 GB 8.54 GB
Wa velength 650 nm 650 nm 650 nm
Reflectivity 18-30% 45-85% 18-30%
Track pitch 0.74 µm 0.74 µm 0.74 µm
Minimum pit length 0.4 µm 0.4 µm 0.44 µm
Modulation >0.6 >0.6 >0.6
Data modulation/ECC 8-16/RS-PC 8-16/RS-PC 8-16/RS-PC
Channel bit-rate 26.16 MHz 26.16 MHz 26.16 MHz
Scanning velocity 1x – 2.4x 3.49 m/s (1x) 3.84 m/s
DVD+RW DVD-ROM
Single-layer Dual-layer
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DVD+ReWritable technology
D VD+ReWritab le and ho w it works
Philips Disc Systems
Building SFF7
P.O.Box 80002
5600 JB Eindhoven
The Netherlands
Philips Media Relations
Jeannet Harpe
Building SFF-6
P.O.Box 80002
5600 JB Eindhoven
The Netherlands
phone +31 40 273 56 77
fax +31 40 273 27 29
It is a criminal offense,under applicable copyright
laws,to make unauthorized copies of cop yrightprotected material,including computer programs,
films,broadcasts and sound recordings.This
equipment should not be used for such purposes.
© 1999 Royal Philips Electronics N.V.
All rights reserved.Reproduction in whole or part is
prohibited without written consent of the copyright
owner .
8/99 Printed in The Netherlands
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