SINGULUS MASTERING BV
15X CD and 5R DVD
CAV, the supporting act for the AM Master
The term CAV stands for Constant Angular Velocity and is used to describe how, in our
business, a disc rotates. Constant angular velocity means that the rotation speed ω is fixed
(e.g. 40 Hz. meaning 40 revolutions per second).
Controlling such a rotation is not too difficult. Once the disc is spinning at the required
speed, its status is stable as all parameters are kept the same.
CAV versus CLV
When looking at storing information on the surface of a disc, a trade-off has to be made
between capacity and accessibility. When fast random access to the data is required, it is
essential to know the exact location. This can be achieved by rotating the disc in CAV mode
and using concentric circles divided in sectors to store the information. Such method is used
in hard disks, which rotate typically at a fixed speed of 5400 to 15000 rpm. Disadvantage of
the approach is that the linear density of the data is less towards the outside of the disc, thus
“wasting” capacity.
When the goal is to pack as much data as possible on a disc, the linear density should be
maximal on any location of the disc. Therefor we are looking at a Constant Linear Velocity
(CLV) mode of operation on read-out. This is exactly what is used for CD, DVD, DH DVD
and BD formats in order to maximise capacity. Random access is possible, as the data is
organised in sectors, but main use is in a sequential manner (Audio, Video).
CAV in use since 1888
Another factor to use CAV can be ease of
design and construction. This has clearly been
the case in the record industry with the
invention of the gramophone by Emile Berliner
in 1888. Gramophone records are rotating at
a fixed frequency of 78 (actually 78.26), 33⅓,
45 rpm. In other words: CAV. As a
gramophone record is read from outside to
inside, the CAV mode resulted in increased
"end-groove distortion" toward the centre of
the disc, particularly on loud passages.
Although this problem was know, it never
resulted in gramophone discs in CLV mode. In
the manufacturing process, the master was
also recorded in CAV mode, then plated and
used for replicating the discs.
CLV in Optical Disc Mastering
A mastering system records data onto a blank
substrate covered with photo resist. As the
read-out data-rate for CD and DVD is CLV, it
was logical to choose this mode for recording
of the disc. Challenge became the control of
the rotation of the motor, as rotation speed
decrease moving from inside to outside of the disc following 1/r. This was brought under
control in the embedded software of the laser beam recorder.
May 2006
SINGULUS MASTERING BV, Marinus van Meelweg 2, 5657 EN Eindhoven, The Netherlands
Tel: +31 40 7501 400 Fax: +31 40 7501 409 E-Mail: [email protected] Web: http://www.singulus.nl
SINGULUS MASTERING BV
Encoding speed, focus system response time and required recording laser power all remain
constant due to the constant linear velocity. Progress in computing power have resulted in
increase of the recording speed from 1X CD to 10X, and from 1R DVD to 4R on modern
days machines.
Comparing CAV, CLV
The two methods each have their pros and cons, resulting from the different properties.
typical values for DVD
Rotation speed
Linear velocity
Translation speed
Signal encoding speed
Recording time PA
Average speed
CLV
69 - 29 Hz
15 m/s (fixed!)
48 – 20 µ/s
3R
20 minutes
3R
CAV
70Hz (fixed!)
10-25 m/s
50 µ/s
3 – 7.3R
12 minutes
5.2R
In CLV mode, rotation speed is at its maximum at the inner radius, thus limiting the
mastering speed for the complete disc. This is the reason that the LBRs with 240mm glass
were limited to 4X, 2R recording speed.
When the same rotation speed is maintained in CAV mode we see that the linear velocity
ramps up towards the outside of the disc, thus creating a challenge for the focussing system,
the encoder, and the required laser power. All three can be limiting for the machine
performance.
CAV in Mastering
Using CAV in mastering is only possible when the signal source, the encoder, can deliver its
data (EFM) in a linear increasing or decreasing manner. This requires the encoding clock
speed to be tightly controlled from beginning to end of the recording. Singulus Mastering
introduced CAV mastering for CD and DVD on the Big Stone in May 2003, thus boosting the
capacity by 50%.
With the introduction of the ACE250 encoder, which boosts a maximum encoding speed of
250 MHz, CD can be encoded at speeds beyond 40x and DVD at almost 10R. This enables
Singulus Mastering to offer the AM Master with average mastering speeds of 15X for CD
and 5R for DVD. Speeds on the outside of the discs are over 20x and 7.2R respectively.
Challenge is now with the LBR itself, in particular the focussing system as the linear velocity
goes up to 25m/s. A novel focus system part of the 15X, 5R package takes care of this. A
Learning Feed Forward Control (LFFC) system anticipates the surface profile of the
substrate from revolution to revolution. This makes it possible for the system to react faster
on surface height changes during the mastering.
What does it bring
CAV enables the AM Master to perform at 15X, 5R, thus making the next step in daily
mastering capacity and further shortening time required for a mastering session.
It also brings a challenge to the encoder, more particular to the storage as a sustained user
data rate of at least 25 Mb/s for CD and 88 Mb/s for DVD must be supported.
Encoder speed
15x
5R (using CAV)
8x
3R
4x
2R
CD production in 24h
166
118
75
DVD production in 24h
76
58
38
May 2006
SINGULUS MASTERING BV, Marinus van Meelweg 2, 5657 EN Eindhoven, The Netherlands
Tel: +31 40 7501 400 Fax: +31 40 7501 409 E-Mail: [email protected] Web: http://www.singulus.nl